Docstoc

Paediatric Ophthalmology notes eyenz homepage

Document Sample
Paediatric Ophthalmology notes eyenz homepage Powered By Docstoc
					 PAEDIATRIC OPHTHALMOLOGY NOTES 2004

Graham Wilson
Dept of Ophthalmology
January 2004

                              CONTENTS

      1.    Visual Development/Assessment of Vision                            1
      2.    The Apparently Blind Infant                                        2
      3.    Amblyopia                                                          4
      4.    Strabismus (Squint)                                                5
      5.    Examination Techniques for Strabismus                              8
      6.    Treatment of Amblyopia                                            10
      7.    Treatment of Squint                                               11
      8.    Refractive errors                                                 12
      9.    The Red Eye in Childhood                                          13
      10.   Conjunctivitis in the infant & older child                        16
      11.   Corneal Disease                                                   18
      12.   Blocked Tear Ducts                                                20
      13.   Trauma                                                            22
      14.   Leukocoria/Retinoblastoma/Congenital cataract                     24
      15.   Infantile Glaucoma                                                24
      16.   Orbital Disorders                                                 26
      17.   Learning Disabilities                                             28
      18.   Squint Terminology (Table 1)                                      30
      19.   Refraction Terminology (Table 2)                                  31
      20.   Summary (Table 3)                                                 32



                                                 Suggestions re improvements to
                                                 these notes are always welcome.
Paediatric Ophthalmology Notes 2004                                                Page 1

                VISUAL DEVELOPMENT / ASSESSMENT OF VISION

Eye disorders in the infant and child are relatively common. About 3% of children will
fail to develop their full visual potential in at least one eye. The ability to detect eye
disorders during childhood is essential for all doctors who deal with children.

The Development of Vision in Childhood

Vision is a developed sense. The period of visual immaturity extends from birth until
about age eight. The most crucial time for visual development is the first (3) few
months of life. The development of equal, normal vision in both eyes requires clear
focussed images on the same point in each retina during the period of visual
immaturity. Any factor which interferes with visual development will cause poor vision
in the affected eye(s) (amblyopia = lazy eye) unless it is corrected for during the period
of visual development. Examples of such adverse factors are: large refractive errors,
misaligned eyes or ocular media opacities such as congenital cataract. When a sight
threatening disorder is present in early life, prompt intervention offers the best chance
of ultimately obtaining useful vision.

Assessment of Vision in Children

The first priority when examining the visual system of a child is an assessment of the
child‟s visual performance. Make your examination into a game and you will get
results. Toys to catch the child's attention are essential. A good ophthalmoscope,
preferably with a rechargeable handle and a quartz halogen bulb (to give a constant
bright illumination) is also required. Keep the uncomfortable parts of the examination
(such as eye drops and fundus examination) for last.

Screening for Visual Disorders in Infancy

This may be limited by the co-operation and developmental stage of the child. The
examination should be directed by the parent‟s complaints and the child's symptoms.
The basic tests in a child under three years of age are:

         Gross examination (External)
         Visual interest (visual following and fixing) (a toddler with normal vision
          should be able to identify 100‟s and 1000‟s at 1 metre)
         Bruckner reflex (see later)
         Ocular Alignment
         Pupil responses
         Ophthalmoscopic examination through dilated pupils including an
          assessment of the red reflex.
Paediatric Ophthalmology Notes 2004                                             Page 2

Gross Examination and Visual Interest

In the gross examination, look for disorders of the lids and for red eyes. The onset of
an infant‟s ability to fix and follow is usually seen at about six weeks of age. Always
ask the parent what visual behaviour has been observed. Does the child have an
abnormal head position? If a child is not fixing and following a target, such as a
penlight, by the age of three months, expert assessment is called for. Nystagmus in
infancy always requires referral to an ophthalmologist.


THE APPARENTLY BLIND INFANT

Practice point: always needs urgent referral to an ophthalmologist

The apparently blind infant with nystagmus

Always trust the mother if she tells you her baby can‟t see. Children with bilateral
disorders of the anterior visual pathway eg albinism, cataract or retinal dystrophy
usually develop sensory deprivation nystagmus at around about three months of age.
Sensory deprivation nystagmus usually has a pendular (searching) quality although
many such children will also have a jerk component to the nystagmus. If nystagmus
develops in the new born period it is most likely due to congenital (motor) nystagmus
which is due to a mis-wiring of the cerebellum. This disorder may be inherited so a
family history should always be sought. It is important to realise with infantile
nystagmus that many of the patterns of nystagmus overlap so that the type of
nystagmus, while it gives a clue to the diagnosis, cannot be the only basis for making
a clinical diagnosis. An underlying disorder should always be sought -referral to an
ophthalmologist is strongly recommended. Electrophysiological testing of the visual
system (eg an electroretinogram [ERG]) is now part of the standard workup of an
infant with nystagmus. Any nystagmus with onset after 6 months of age is likely to be
neurological, although neurological causes of nystagmus in infants are rare.

The apparently blind infant without nystagmus

Infants with poor vision who do not have nystagmus may simply have delayed visual
maturation. This disorder is thought to be due to delayed myelination in the occipital
cortex. Such infants are usually otherwise neurologically normal. The vision usually
comes up to normal by age one. The diagnosis is usually made in retrospect.
Cerebral vision impairment (CVI) refers to visual failure due to brain damage. The
vision often fluctuates on a day to day basis. These children almost always have other
neurological signs. CVI may follow intraventricular haemorrhage in premature infants
or other neurological insults such as birth asphyxia, meningitis, trauma or near death
drowning. Some recovery almost always occurs in time but may take some years.
Cerebral vision impairment is now the most common cause of poor vision in childhood
Paediatric Ophthalmology Notes 2004                                                  Page 3

(followed by optic nerve hypoplasia and retinopathy of prematurity).

Because a child with poor eyesight from infancy may suffer from delayed
development, a referral to an agency which can provide support and an appropriate
program of stimulation is strongly recommended.

Pupil Responses

The pupil responses should be checked when the child is fixating a distant target.
Test each eye separately first, then swing the light from one eye to the other in order
to detect an afferent pupillary defect. This is the paradoxical dilation of the pupil of the
affected eye when the torch is swung from a normal eye to one affected by optic nerve
disease.

Ophthalmoscopic Examination

Fundus examination in the infant requires skill and patience, and is best left to last.
The fundus must be examined through a dilated pupil if you are serious about seeing
anything. For infants below one year of age use one drop of 0.5% Cyclopentolate
(Cyclogyl) or 1.0% Tropicamide (Mydriacyl) for mydriatic purposes.

At arm's length, assess the red reflex (the defocused fundus reflection); this will detect
any opacities in the ocular media such as cataracts. Also look at the Bruckner reflex
(simultaneous comparison of the fundus red reflexes [see later]). Then examine the
external eye with the ophthalmoscope racked up to +10.                     Then set the
ophthalmoscope at your own refractive error or leave your glasses on with the
ophthalmoscope set at 0. Come in to examine the fundus about 15 off axis
temporally. This will bring the optic disc into view. The additional lenses which you
need to rack up on the ophthalmoscope to obtain a clear image of the retina will
provide you with a rough assessment of the patient's refractive error. After examining
the disc for cupping, swelling or pallor, follow the retinal vessels out in each quadrant
and complete the examination of the fundus by looking at the macular area, found
about 1½ disc diameters temporal to the disc.

Screening for Visual Disorders in the Older Child

In the older child, first obtain a visual acuity. Over three years of age single letter
testing is the easiest method providing that one accepts that it may miss some
amblyopes because of the `crowding' phenomenon. The crowding phenomenon
(caused by the so-called abnormal contour interaction of amblyopic eyes) refers to the
behaviour of amblyopic eyes - they will easily distinguish a single letter on a bland
background but the true acuity of the eye is discovered when the child tries to read a
single letter in a line of letters or a single letter surrounded by confusion bars (see
preferred test below). From about age four the linear `E' chart is quite useful. The
Paediatric Ophthalmology Notes 2004                                                Page 4

Snellen chart can be used once a child knows the alphabet, but abnormal results
should be interpreted cautiously in the five and six year old because of the possibility
of non comprehension of the letter being tested. Take care during acuity testing that
the child is not peeking behind the patch.
The recommended single letter chart is available from The Department of
Ophthalmology, Medical School, University of Otago, Dunedin, New Zealand. Price is
about $6.00NZ + postage. It is calibrated for use at 4.0 meters (useful in real life
consulting rooms). Ask for the „4.0 metre letter matching vision test with confusion
bars‟.
Once the child's visual acuity has been tested, the examination then follows the lines
previously described for an infant. Cyclopentolate 1.0% is better for mydriasis in the
older child than 0.5%.


AMBLYOPIA

The main cause of poor eyesight until middle age is amblyopia (Definition: a reduction
in visual acuity due to abnormal visual experience early in life). Amblyopia is almost
invariably due to some interference with visual development during the period of visual
immaturity. Most cases are treatable if detected early enough.

Types of Amblyopia:

A. Functional Amblyopia

This is the commonest type of amblyopia and is usually diagnosed by finding a
difference in visual acuity between the eyes of two or more lines on the Snellen chart
(or its equivalent) in the absence of organic disease. In younger children, if one eye is
preferred for fixation, amblyopia should be suspected in the non-preferred eye.
Amblyopia is caused by disuse of one or both foveas for visual fixation during the
period of visual immaturity. It is almost always unilateral and is believed to result from
a competition between the two eyes to develop connections with binocularly driven
neurones in the occipital cortex ie it is cortically based. If one eye is at a biologic
disadvantage e.g. a squint or anisometropia (unequal refractive errors), the other eye
with the better image will tend to dominate connections in the cerebral cortex, resulting
in better visual acuity in the favoured eye and amblyopia in the non-favoured eye.
Bilateral amblyopia can result from bilateral visual deprivation (eg bilateral cataracts).

There are four subtypes of functional amblyopia, more than one of which may coexist
in the same patient:

   1. Strabismic Amblyopia. This develops as a defence against diplopia (double
      vision) when the eyes are aligned in two different directions. Any eye which
      squints constantly from an early age will develop strabismic amblyopia. It is
Paediatric Ophthalmology Notes 2004                                               Page 5

       particularly prone to occur in the presence of a convergent squint rather than a
       divergent one probably because convergent squints are more likely to be
       constant than divergent squints, at least in early childhood.

   2. Anisometropic Amblyopia. This is caused by a significant difference in the
      refractive error of the two eyes (anisometropia), particularly if the child is
      hypermetropic (long sighted). It is also relatively common. Affected children
      are usually asymptomatic because they function well using the good vision
      found in one eye. Because anisometropic amblyopia does not often lead to a
      squint, it frequently remains unrecognised until school age when it is detected
      by testing visual acuity separately in each eye. It is easily detected by looking
      at the Bruckner reflex (see later).

   3. Ametropic Amblyopia. This is caused by a large refractive error in both eyes,
      particularly hypermetropia.    Myopia (short sightedness) rarely causes
      amblyopia because the small child's world is close up and the images of near
      objects are in focus in myopic eyes. Ametropic amblyopia is frequently
      associated with a convergent squint.

   4. Deprivation Amblyopia. This occurs when a clear retinal image cannot be
      formed e.g. because of a congenital cataract or a corneal opacity.

B. Organic Amblyopia

This is amblyopia which develops in the presence of organic disease e.g. a structural
abnormality of the eye such as optic nerve hypoplasia or acquired disease such as
retinal scarring from retinopathy of prematurity (formerly known as retrolental
fibroplasia).

In the infant, amblyopia can be inferred when there is a definite fixation preference for
one eye to the exclusion of the other. This is usually seen in the context of a squint.
In the older child, the easiest way to detect amblyopia is by measuring the visual
acuity in each eye.


STRABISMUS (SQUINT)

Misalignment of the eyes on the object of gaze (strabismus) is common during
childhood (up to 5% of children in some series). Transient squints are occasionally
seen in the neonatal period but a constant squint is abnormal at any age. Any squint
seen after the age of six weeks requires formal assessment. There is often a family
history.

Types of Strabismus
Paediatric Ophthalmology Notes 2004                                                   Page 6


The detailed classification of squint is quite complex but it can be simply be classified
as convergent, divergent or vertical. The ophthalmic jargon for squints is in Table 1.

A. Convergent Squint (Esotropia)

1.      Infantile Esotropia

Definition: A convergent squint which manifests itself in the first six months of life. aka
congenital esotropia-a misnomer given that clinical studies have found that the usual
onset is between four and six months of age (when binocular vision develops in
normal infants). The aetiology is unknown but is probably a disorder of the binocular
cells in the visual cortex which detect eye misalignment. The angle of squint is usually
quite large (and hence the squint is usually obvious to the parents). Refractive errors
are not an important cause of squint in this age group, so glasses are uncommonly
prescribed. Eye muscle surgery is usually necessary.

The inability of an eye with organic pathology to fixate may lead to infantile onset
esotropia. It is mandatory when assessing children with infantile onset squints to
exclude such conditions as congenital cataract and retinoblastoma by a dilated fundus
examination.

The squint usually alternates between the two eyes and so amblyopia is uncommon.
Cross fixation is often seen; i.e. the squinting eye is used to fixate in the contralateral
field eg. objects in the left field of gaze will be fixated by a squinting right eye and vice
versa. As a result, neither eye has to abduct as vision out to the side is taken care of
by the fellow eye fixating across the nose; an erroneous diagnosis of bilateral sixth
nerve palsy may then be made. Abduction can usually be demonstrated by spinning
the child around in one's arms and observing a normal doll's eye manoeuvre.

2.      Acquired Esotropia

Definition: A convergent squint appearing after the first six months of life.
This is the second most common convergent squint encountered in clinical practice. It
usually appears between the ages of eighteen months and four years. Hypermetropia
is often an important aetiological factor. Accommodation and convergence are linked
via a neural mechanism (accommodative convergence); in this way when we
accommodate for a near object the eyes converge, so avoiding diplopia. In children,
where hypermetropia is the rule, accommodation is utilised to obtain a sharp retinal
image even for distant objects. Accommodative convergence is counterbalanced by
fusional divergence ie. eyes are kept aligned by the fusion mechanism in order to
avoid diplopia. If fusional divergence is poor, the eyes will begin to converge
whenever accommodation is activated. Ultimately a constant squint will develop. In
the visually immature child, any diplopia caused by this misalignment can be
Paediatric Ophthalmology Notes 2004                                                  Page 7

suppressed. In time, amblyopia can develop in the non preferred eye.

If accommodation is a factor in a convergent squint, the prescription of glasses to fully
correct for the hypermetropia will usually correct the deviation partially or totally. After
correcting any refractive error (often determined by a trial of glasses wear) and
patching to eliminate any amblyopia present, the remaining deviation (if any) is
corrected by squint surgery.

A convergent squint developing in any child should raise the suspicion of a sixth nerve
palsy due to intracranial disease. All children presenting with a convergent squint
should have the optic disc examined through a dilated pupil to exclude papilloedema.
Retinoblastoma should also be excluded even in older children.


B. Divergent Squint (Exotropia)

The aetiology of divergent squints is less well understood than for convergent squint.
Most probably begin with some disorder of innervation; either a weakness of
convergence or an excess of divergence. In the older child (and adult) deprived of
fusion (e.g. by a traumatic cataract) tonic divergence prevails and such an eye will
ultimately diverge. Anatomical factors are also important: shallow orbits such as occur
in many craniofacial syndromes predispose to divergent squint.

Intermittent Exotropia

Most divergent squints have onset in infancy or early childhood. They are usually
intermittent at the time of onset. Fatigue and intercurrent illness can precipitate a
manifest squint. Sunlight also can precipitate a breakdown of fusion resulting in a
frank divergent squint with the diverging eye often closed, probably to avoid diplopia.
The parents may then present complaining that the child is 'screwing up the eye
(squinting) in sunlight'. When the lid is elevated by the examiner, the divergent squint
is noted. The natural history of intermittent exotropia is poorly documented. With
time, many children with this condition squint more often and for longer periods, finally
developing a constant squint. Binocular vision cannot be developing in this
circumstance so surgery is often offered to these children when the squint is manifest
more than fifty percent of the time.

C. Vertical Squints

Small vertical squints due to oblique muscle dysfunction are commonly associated
with horizontal squints. Isolated vertical squints are uncommon in children. There is a
large differential diagnosis. The commonest isolated vertical squint in childhood is due
to a fourth nerve palsy, which is usually congenital or related to trauma. The child
often presents with a head tilt or a face turn, both of which are used to put the eyes
Paediatric Ophthalmology Notes 2004                                                Page 8

into a position where the effect of the palsy on fusion is least. Some infants with
'torticollis' are merely attempting to compensate for a vertical squint. Unless there is
an obvious lesion of the sternomastoid, infants with torticollis should be assessed by
an ophthalmologist to avoid missing a congenital fourth nerve palsy.

Third nerve palsy may also lead to a vertical squint. The causes in childhood include
congenital, trauma and ophthalmoplegic migraine. Because of the large differential
diagnosis, children with a vertical squint should be referred to an ophthalmologist
without delay.

Strabismus, Amblyopia and Refractive Errors

There is an interaction between squint, amblyopia and refractive errors. For example,
an eye which squints constantly from an early age will almost certainly become
amblyopic, and an eye which becomes amblyopic for some reason e.g. a unilateral
cataract will often develop a squint. Large refractive errors, especially hypermetropia
(long sightedness) may produce strabismus or amblyopia or both together.


EXAMINATION TECHNIQUES FOR STRABISMUS

The detection of a squint is accomplished by discovering a misalignment of the eyes.
Firstly, carry out one or all of the tests described below, to check for the presence of a
squint. Then test the eye movements by getting the child to follow a toy in the
direction of each individual extraocular muscle.

The easy methods for determining whether or not a squint is present are to assess the
asymmetry of the corneal light reflections (Hirschberg corneal reflex test), to look for
the Bruckner reflex (fundus red reflexes compared) and to carry out the cover tests.
The cover tests should be carried out using both near (to stimulate accommodation)
and distant targets. Use toys to attract the child's attention.


The Hirschberg (corneal reflex) test

This test relies on detection of asymmetry of the corneal light reflections (reflexes).
Attract the child's attention to a penlight and compare the light reflex on each cornea.
Very few people look through the dead centre of the cornea; most fixate slightly nasal
of centre (positive angle kappa). Look for asymmetry of the two light reflexes. If the
light reflex in one eye is displaced temporally then that eye has a convergent squint
and vice versa for a divergent squint.

The Hirschberg test is also very useful in the diagnosis of pseudo-squint. Pseudo-
squint is readily diagnosed when the corneal light reflexes are observed to be
Paediatric Ophthalmology Notes 2004                                                   Page 9

symmetrical in a child with an apparent squint. The pseudo squint appearance is due
to the fact that more sclera is visible nasally in one eye than the other, usually because
of asymmetry of the epicanthic folds. Parents often mistake this appearance for a
squint.

The angle of misalignment of squints can be estimated using this method. If the
corneal reflex in one eye is approximately central and the other reflex is displaced to
the limbus then the deviation is 45; if the light reflex is only half way to the limbus then
the deviation is 22, and so on.

The Bruckner Reflex

This test compares the fundus red reflexes when viewed at arms length through a
direct ophthalmoscope (unfortunately, you can‟t do this test with the Panoptic
ophthalmoscope). The room should be darkened and the lens wheel in the
ophthalmoscope set at zero. An ophthalmoscope with a rechargeable handle and a
halogen bulb is best.

The infant's attention should be attracted to the ophthalmoscope (this usually happens
naturally). In the normally fixating child, the light from the ophthalmoscope globe is
reflected back from the centre of the fovea - as in a concave mirror. If one eye is not
fixating centrally, then the light will be scattered and will enter the viewing hole of the
ophthalmoscope. The affected eye will have a brighter reflex than its fellow. The
Bruckner reflex is over 95% sensitive at picking up amblyopic eyes, but there is a
significant false positive rate. Anisometropia (unequal refractive errors) is easily
detected by this method. If one eye is very hypermetropic, the reflex will look dull due
to defocus of light within the affected eye. The important principle to grasp is to detect
asymmetry of the red reflexes. The test is not sensitive in very small infants less than
6-9 months of age but is very useful in children about eighteen months of age who do
not like being examined at close range, eg with the cover tests.


The Cover Tests

These rely on the fixation reflex. If vision in an eye is so poor that it cannot take up
fixation then the cover tests will not work. Accommodation should also be controlled
preferably with the child's glasses on (if needed) and using a toy to stimulate
accommodation. A hand held torch is not an adequate target for the cover tests. Test
both near and distance because some children converge at near only and others
diverge at distance only.

Firstly, the cover-uncover test; once the child is fixating, cover one eye and watch the
uncovered eye for any movement in or out to take up fixation. If after a few seconds
there is no movement of the uncovered eye the assumption can be made that there is
Paediatric Ophthalmology Notes 2004                                               Page 10

no manifest (constant) squint in that eye. Now remove the cover and then place it in
front of the other eye, if again there is no movement of the uncovered eye then no
manifest squint is present in either eye. The test has demonstrated that each eye is
fixating simultaneously with its fellow. If, however, the uncovered eye moves to take
up fixation then a manifest squint is present. If the eye moves out to take up fixation, a
convergent squint is diagnosed. Similarly, if the eye moves in to take up fixation a
divergent squint is present in the uncovered eye. Then do the alternating cover test.

The alternate cover test detects latent squints i.e. those held in control by the fusion
mechanism. If fusion is suspended by covering up one eye (this prevents diplopia
being experienced), latent squints develop behind the cover. Simply place the cover in
front of one eye, hold it there for a few seconds and move it briskly across to the other
eye, watching the eye you are uncovering. If the eye being uncovered moves to
refixate it must have deviated behind the cover, i.e. a latent squint is present. The
alternate cover test also detects manifest (constant) squints as well.

The angle of squint can be measured in conjunction with the cover tests by using
plastic prisms of varying power. Ophthalmologists may report the size of the deviation
in prism diopters if they have measured the deviation using prisms. The conversion to
degrees is simple; one degree equals approximately two prism diopters.

The cover tests will detect all but very small angle squints (micro-squints) where the
refixation movement is often too small to detect. Fortunately micro-squints are
relatively uncommon and significant amblyopia associated with a micro-squint will be
detectable by measuring the visual acuity.

Latent Squint

Latent squints do not have the potentially serious connotations of manifest squints
because amblyopia cannot develop while the eyes are fusing. They can lead to
problems, however, if the fusion mechanism has little reserve to keep squint under
control. The patient may then develop symptoms of eye strain and intermittent
diplopia, often for close work. Glasses, orthoptic exercises and occasionally even
surgery may be necessary to relieve the symptoms. Most people have a latent
divergent squint (exophoria) at near. The mere presence of a latent squint does not
indicate a problem unless there are relevant symptoms and signs. A slow realignment
of the eyes after removing the cover following the alternate cover test, indicating poor
fusion ability, is usually seen in those latent squints which are producing symptoms.
Intraocular disease rarely, if ever, produces a latent squint.


TREATMENT OF AMBLYOPIA

The principles of treatment of amblyopia are simple: patch the good eye to force
Paediatric Ophthalmology Notes 2004                                              Page 11

usage of the affected eye, correct any refractive error (usually by the prescription of
glasses) and remove the cause if possible (e.g. by squint surgery). Strabismic
amblyopia should always be corrected prior to squint surgery to ensure the maximum
possibility of a stable post operative alignment. Treatment of amblyopia is now
supported by several randomised controlled trials.


TREATMENT OF SQUINT

Treatment should begin as soon as the squint is diagnosed. Aside from transient
squints in the neonatal period, very few children will spontaneously straighten a
constant squint. Thorough examination is necessary to exclude organic pathology.

Treatment is necessary to enable binocular fusion to develop (which will predispose to
a stable alignment) and to improve the child's appearance. Treatment may involve
prescription of glasses, patching and surgery or a combination of these.

Squint surgery involves either reducing the pull of a muscle (recession) or tightening of
a muscle (resection). Most squint operations involve surgery on two muscles and take
about 35 minutes. Up to six muscles between the two eyes may be operated on at
one time. Complications are rare. Soft tissue infection occurs in about 1 in 500 cases.
  Loss of an eye or blindness occurs in less than 1 in 50,000 cases.

The success rate of surgery for infantile esotropia is about 80% for one operation.
Further operations may be necessary if there is an over or under correction with the
first procedure or if vertical muscle dysfunction develops. Forty per cent of children
treated surgically for an infantile esotropia will ultimately develop an accommodative
component and require glasses during childhood.

Parents should be advised that continual supervision of a child with a squint is
necessary until the child is visually mature (about age eight), regardless of whether
treatment has realigned the eyes or not. A successful operation at an early age may
be undone if the child is lost to follow up and amblyopia develops unrecognised.

It should be re-emphasised that a squint may occasionally be the presenting sign of
serious intraocular or intracranial disease. In the case of retinoblastoma, the eye
disease is life threatening. All children with squint should be considered to have a
retinoblastoma until proven otherwise by a dilated fundus examination. Papilloedema
should likewise be excluded.


REFRACTIVE ERRORS

Refractive errors are important causes of amblyopia and strabismus in the younger
Paediatric Ophthalmology Notes 2004                                                 Page 12

child and infant. In the older child, refractive errors may cause problems in school.
Terminology is in Table 2.

Signs and Symptoms of Refractive Errors in Children

These are many and varied and are said to include blinking, frowning, rubbing the
eyes, head tilting, closing one eye, clumsiness, photophobia, red eye and epiphora
(tearing). In practice these symptoms are only rarely explained by refractive errors. In
the younger child and infant, refractive errors are most likely to present as a squint. In
the older child, refractive errors may cause school problems with an inability to read
the blackboard or visual fatigue on prolonged close work. Headaches in children are
rarely due to refractive errors. In this case, there is usually a clear association
between visual effort and the onset of headache.

Diagnosis of Refractive Errors

In the younger child and infant, refractive errors should be excluded if squint or
amblyopia is diagnosed. A significant refractive error can be suspected if you must
rack up more than -l or +3 on the ophthalmoscope to get a clear fundus view through a
dilated pupil with the viewers refractive error is taken into account. Precise
measurement of refractive errors in children is possible using a retinoscope.

In the verbal child, refractive errors should be suspected if the child complains of
blurring of vision particularly for distant objects such as the blackboard, of if there is a
complaint of visual fatigue especially after visually demanding tasks such as reading.
The task of deciding whether a refractive error is present is made much easier in the
older child because visual acuity can be formally assessed for distance on the Snellen
chart and for near using a near reading card. In the over 5 year old, if uncorrected
distance vision is less than 6/9 and near vision is good, myopia should be suspected.
If blurred vision clears when looking through a pinhole, a significant refractive error is
almost certainly present


Treatment of Refractive Errors

Refractive errors causing symptoms or suspected of causing a squint are prescribed
appropriate glasses or contact lenses. Anisometropia requires treatment if the
difference between the two eyes is sufficiently large to cause amblyopia (in the
hypermetropic child one diopter of difference between the eyes can cause amblyopia).
 Very few children or adults are truly emmetropic and many children are prescribed
glasses unnecessarily for trivial deviations from the 'norm'. An association between
mild or moderate refractive errors and school performance is at best a tenuous one.
In the interest of preventing eye trauma, 'glasses' for children are made with plastic
lenses which have a much greater impact resistance than glass.
Paediatric Ophthalmology Notes 2004                                               Page 13


Laser surgery for refractive errors has no place in childhood because eye shape and
growth are dynamic processes until late adolescence.


THE RED EYE IN CHILDHOOD

The diagnosis of the 'red eye' in childhood follows conventional medical lines; i.e.
taking a history, carrying out an examination and looking for pathognomonic groupings
of symptoms and signs. 'Shotgun' treatment of all red eyes with antibiotic-steroid
drops in the first instance is quite irrational and potentially dangerous. For instance
steroid drops can lead to severe keratitis in the case of unsuspected Herpes simplex
infection.


CONJUNCTIVITIS

The symptoms of conjunctivitis are red, itchy, irritable eyes and a discharge. The
discharge varies from purulent in the case of bacterial conjunctivitis to watery in
allergic conjunctivitis. Conjunctivitis is usually bilateral. Vision is unaffected unless
keratitis develops.

On examination, the conjunctiva over the inside of the eyelids (tarsal conjunctiva) is
injected, particularly in the fornices, but the conjunctiva over the eyeball (bulbar
conjunctiva) is not affected to the same degree i.e. the eyeball is not as red as the
inside of the eyelids or the redness is maximal in the lower fornix. Leakage from
conjunctival capillaries (papillae) will cause the tarsal conjunctiva to have a velvety
appearance. Lymphoid follicles on the tarsal conjunctiva are seen in acute trachoma
and viral conjunctivitis.     Chemosis (conjunctival oedema) is seen in severe
conjunctivitis.

If the redness of the eyeball itself is maximal at the limbus (ciliary injection) then the
cause of the inflammation is within the eye and the diagnosis of conjunctivitis should
not be made. Pain, photophobia and excessive lacrimation always indicate that there
is corneal involvement (keratoconjunctivitis) and should lead to ophthalmic referral.

Points to remember about making the diagnosis of conjunctivitis; If the redness
remains unilateral, if the vision is affected or if there is severe pain, alternative
diagnoses such as keratitis (corneal inflammation) or iritis should be seriously
considered.

Ophthalmia Neonatorum

Ophthalmia Neonatorum refers to any severe conjunctivitis which occurs in the
Paediatric Ophthalmology Notes 2004                                              Page 14

newborn period. The clinical picture is usually that of a severe conjunctivitis which
may occur any time from the first day of life. While there are certain characteristic
clinical pictures (see later) there is marked overlap in the clinical picture caused by
different organisms so urgent laboratory investigations are called for to enable
appropriate treatment.

The major causes of ophthalmia neonatorum in Australia are Chlamydia trachomatis
and bacteria such as Staph, Strep and Pseudomonas. Gonococcal conjunctivitis is
rare but devastating.
Urgent investigation and treatment must be instituted. An immediate gram stain and
Chlamydia PCR is called for, followed by culture for the usual organisms. The
immediate advice of an ophthalmologist should be sought if ophthalmia neonatorum is
suspected. After the first week of life, blockage of the nasolacrimal duct can
occasionally predispose to mild conjunctivitis. Neonates often have a mucoid
discharge which dries on the eyelids; this is not infective and requires eye toilet only.
Because silver nitrate prophylaxis is not used in NZ, this is not a cause of severe
(chemical) conjunctivitis in neonates in this country. This is a notifiable disease.

A. Gonococcal Conjunctivitis

Ophthalmia Neonatorum is a medical emergency. The child may be blinded within 24
hours of onset if Gonococcus is the organism responsible because Gonococcus (and
also Pseudomonas) can rapidly penetrate even an intact cornea. The signs are a
profuse purulent discharge from the eyes which is usually accompanied by marked
conjunctival chemosis. In addition there is often marked redness and swelling of the
eyelids. The pus may be under pressure and spurt out when the lids are forced open.
 It is imperative to diagnose Gonococcus by an immediate gram stain and to send off
swabs for culture in appropriate transport media. For Gonococcal ophthalmia,
systemic antibiotics, eg Ceftriaxone, are essential in order to obtain adequate tissue
levels and to prevent systemic spread of the organism. Gentamicin drops may also be
used as an adjunct to systemic therapy. Saline toilets to remove pus from the eye are
useful but extreme care must be taken not to abrade the cornea.

B. Chlamydial Conjunctivitis
This usually appears several days after birth and may be clinically indistinguishable
from Gonococcal conjunctivitis. Like the Gonococcus, the infective organism,
Chlamydia trachomatis, is transferred from an infected mother during birth. The
diagnosis is made by detecting positive immunofluorescence (or by PCR) for
Chlamydia and by a negative Gram stain for Gonococcus. Because of the risk of
pneumonitis, systemic erythromycin should be used (for 3 - 4 weeks). As with
Gonococcal conjunctivitis, the mother and her sexual partner(s) should be investigated
and treated appropriately.

C. Other Organisms
Paediatric Ophthalmology Notes 2004                                             Page 15


Treatment for severe conjunctivitis in the newborn should initially be based on the
gram stain results, if possible, while awaiting culture conformation. The choice of
whether to treat topically or to include systemic antibiotics is a clinical one.
Pseudomonas should be treated with both topical and systemic antibiotics.

D. Herpes Simplex Conjunctivitis

Occasionally, children born to mothers with active genital herpes will be infected, and
may present with a severe follicular conjunctivitis in the first few days of life. There
may be an associated infection of the surrounding skin of the eyelids which will show
vesicles. The diagnosis, which is often made clinically, can be confirmed rapidly by a
fluorescent antibody technique, backed up by virus culture. If the cornea becomes
involved, treatment with antiviral agents (sometimes even intravenously) is
recommended as for dendritic ulcer. A severe generalised infection may rarely
develop with chorioretinitis and encephalitis. It is often fatal.


PRACTICE POINT - If Chlamydia conjunctivitis is suspected, always take a firm
scraping of the tarsal conjunctiva so that epithelial cells are available for immuno-
fluorescence staining or PCR.


CONJUNCTIVITIS IN THE INFANT AND OLDER CHILD

A. Bacterial Conjunctivitis

This is the commonest type of conjunctivitis seen in childhood. Bacterial conjunctivitis
causes a purulent discharge and is almost invariably bilateral by the time the doctor is
consulted. The organisms responsible are usually respiratory pathogens such as
Pneumococcus or Haemophilus. In severe cases, there may be a pseudomembrane
on the tarsal conjunctiva. Most cases are self limiting but treatment is recommended
because conjunctivitis is contagious and complications such as corneal infection,
although rare, are potentially disastrous. Children with acute conjunctivitis should be
kept away from daycare or school.

If the clinical diagnosis is certain, culture is unnecessary unless there are grounds to
suspect a virulent organism such as Gonococcus or if the conjunctivitis is particularly
severe. Because of its broad spectrum, topical chloramphenicol is still the best drug
for routine treatment of bacterial conjunctivitis (Use 0.5% drops 2nd or 3rd hourly and
1% ointment at night for 3 days). Make sure the parent knows how to instill eye drops.
Do not use chloramphenicol for more than a few days at a time as bone marrow
suppression can occur with long term use although it is extremely rare after eye drops.
 Neosporin or Framycetin are acceptable alternatives. If there is no significant
Paediatric Ophthalmology Notes 2004                                              Page 16

improvement after three days of treatment, either the wrong drug is being used or the
diagnosis is wrong.

B. Viral Conjunctivitis

The signs which distinguish viral from bacterial conjunctivitis are that the discharge is
mucoid or muco-purulent rather than frankly purulent and in viral conjunctivitis there is
frequently an enlarged, tender pre-auricular lymph node present on the affected side.
Viral conjunctivitis frequently begins unilaterally and may be associated with a
concomitant upper respiratory tract infection. A wide variety of viruses has been
implicated and includes adenovirus and herpes simplex virus. In the case of
Adenovirus types 8 and 19 secondary involvement of the cornea is common within a
few days. Adenovirus keratoconjunctivitis may take several months to resolve.
Treatment of viral conjunctivitis is symptomatic; use drops such as Liquifilm tears to
relieve discomfort. Most cases are self limiting and last 14-21 days. The use of
antibiotic-steroid combination drops has no place in the management of bacterial or
viral conjunctivitis.

C. Allergic Conjunctivitis

This is commoner in the older child and may be associated with hay fever or asthma.
The eyes are itchy and irritable and there may only be excessive tearing or a stringy
discharge. Inspection of the tarsal conjunctiva may reveal numerous small papillae
(areas of oedema surrounding dilated capillaries).

D. Vernal conjunctivitis

This is the most severe form of allergic conjunctivitis and is characterised by much
larger papillae than those seen in the milder forms of allergic conjunctivitis. It is
usually seen in late childhood or early adolescence. There is a seasonal incidence
with the disease being most severe in spring and summer. There is usually a history
of asthma, eczema, hay fever or hives. The symptoms are extreme itchiness and
mucoid discharge which is often described as stringy or ropy. Photophobia may
become prominent if the cornea is affected. Giant papillae will be seen, especially
under the upper lid, where they have a flat topped, `cobblestone' appearance.
Gelatinous papillae may be seen at the limbus.

The papillae under the upper lid may attain such a size as to interfere with corneal
function causing the formation of an oval shaped, superiorly located corneal ulcer.
Vision may be severely affected as corneal scarring often follows. The disease usually
burns itself out by the late teens. There is an association between vernal conjunctivitis
and the development of keratoconus (conical cornea) in the later years.

Simple allergic conjunctivitis can be treated with cold compresses or astringent drops.
Paediatric Ophthalmology Notes 2004                                               Page 17

 Systemic antihistamines are sometimes necessary. In a severe acute attack
vasoconstrictors (eg 1/8% phenylephrine) and ice packs may be called for. Vernal
conjunctivitis requires topical steroids in the first instance with long term maintenance
using mast cell / histamine release inhibitors (eg cromoglycate, lodoxamide or patanol
drops) if possible. Desensitisation has not been shown to be an effective treatment.
Because of the risks associated with long term topical steroid use, such as glaucoma
and cataract, the advice of an ophthalmologist should be sought when managing
vernal conjunctivitis.

E. Trachoma

Trachoma in Australia is common in Aboriginals living in conditions of substandard
housing and poor hygiene. It is spread by personal contact or by flies. Vision loss
from trachoma begins in adulthood and follows repeated attacks in childhood which
produce scarring of the conjunctiva. This in turn may lead to corneal scarring.
Epidemics of bacterial conjunctivitis occurring in children with trachomatous scarring
are more likely to lead to complications because the defensive barriers of the external
eye have been compromised.

There are few symptoms of trachoma in an endemic area. The diagnosis is made by
finding prominent lymph follicles in the upper tarsal conjunctiva and at the limbus.
Scarring of the upper cornea (pannus), within which there are clear areas at the former
sites of the limbal follicles (Herbert's pits), is seen in chronic cases. This combination
of signs is pathognomonic of trachoma.

Systemic treatment with co-trimoxazole or erythromycin, both of the patient and the
other persons sharing the dwelling is recommended for three weeks. Systemic
treatment serves several purposes; the cycle of infection and reinfection from other
family members is broken, chlamydial disease elsewhere in the body (eg the middle
ear and the genital tract) is treated and the over burden of bacterial infection, in the
respiratory system and both the external and middle ear is also reduced, leading to
improved resistance.


CORNEAL DISEASE

The characteristic symptoms of corneal disease are pain, lacrimation and
photophobia. Note that none of these symptoms occur in conjunctivitis. Establishing a
prior history of trauma, ocular herpes or the instillation of drops, particularly steroid
drops, is essential. Patients with corneal ulcers often have intense blepharospasm so
examination in these cases should be preceded by the instillation of a local
anaesthetic drop eg amethocaine 0.5%. Examination using a good light, magnification
(+10 on the ophthalmoscope will do) and the instillation of a dye such as fluorescein to
stain epithelial defects is the key to making a correct diagnosis. The shape and
Paediatric Ophthalmology Notes 2004                                              Page 18

location of a corneal ulcer will often provide clues to the diagnosis. Always evert the
eyelids when dealing with a patient with corneal disease - occasionally the kitchen sink
(or a smaller foreign body) falls out from under the upper eyelid!

A. Herpes Simplex Keratitis

Herpes simplex keratitis is an uncommon cause of `red eye' in children but it is the
most common corneal infection in childhood. The result of misdiagnosis or
inappropriate treatment can be a lifetime of poor vision and ocular discomfort. There
may be a history of a previous episode of primary infection. The virus particles remain
dormant in the trigeminal ganglion and invade the cornea when reactivated via the first
division of the trigeminal to produce the typical dendritic ulcer. Reactivation can occur
following exposure to bright sunlight, during menstruation or during periods of stress
such as an intercurrent illness. Intense pain is not a usual feature of dendritic ulcers.

The diagnosis is made by firstly instilling fluorescein into the eye and then examining
the cornea, preferably with a cobalt blue light, looking for the characteristic dendritic
lesions. The management of herpes simplex keratitis is to use an antiviral such as
idoxuridine Acyclovir (Zovirax) ointment 5 times a day. Because of the risk of
complications, ophthalmic referral is strongly recommended. Dendritic ulcers are often
recurrent so the parents should be advised to return immediately if the child's eye ever
becomes red again.

B. Foreign Body/Trauma

Corneal foreign bodies usually cause intense discomfort. The child may not admit to a
history of a foreign body entering the eye or may not be able to tell you. This
diagnosis should be suspected in a child with an unilateral red eye associated with the
signs of corneal disease.

The removal of a corneal foreign body requires a co-operative patient, good topical
anaesthesia, good lighting, a sharp instrument (such as a 19G needle mounted onto a
2cc syringe), magnification and support for the operation's hand. In the younger child
general anaesthesia is often necessary to allow an adequate examination for
diagnostic purposes and to allow the removal of corneal foreign bodies.

Other causes of the red eye which enter into consideration in adults such as scleritis
and angle closure glaucoma are extraordinarily rare in childhood and for practical
purposes need not be considered in the paediatric age group. Uveitis does occur but
it is uncommon unless associated with a systemic disease such as juvenile
rheumatoid arthritis (where routine ophthalmic surveillance is always necessary).


PRACTICE POINTS (RED EYE)
Paediatric Ophthalmology Notes 2004                                                Page 19


*      The correct diagnosis of red eye in childhood is made by seeking
       pathognomonic groupings of signs and symptoms.

*      If the redness remains unilateral, the vision is affected or if there is severe pain
       the diagnosis is not conjunctivitis.

*      Pain, lacrimation and photophobia should always suggest corneal disease.

*      If chlamydial conjunctivitis is suspected, always take a firm scraping of the
       tarsal conjunctiva so that epithelial cells are available for immuno fluorescent
       staining or PCR.

*      If bacterial conjunctivitis does not respond to adequate treatment within three
       days, you have the wrong drug or the wrong diagnosis.

*      In conjunctivitis the redness of the conjunctiva is maximal on the eyelids and in
       the lower fornix. Discharge must be present to diagnose conjunctivitis. If the
       redness is maximal on the eyeball suspect corneal or intraocular disease.

*      There is no place for combination antibiotic - steroid drops in the management
       of bacterial or viral conjunctivitis.

*      Always suspect trauma as a cause of an explained red eye in a child.


BLOCKED TEAR DUCTS

Introduction

Blockage of the naso-lacrimal duct usually presents in the first few months of life with
epiphora (watering eyes) or as mild recurrent conjunctivitis. The nasolacrimal duct,
which connects the lacrimal sac to the nasal cavity begins to form by about the sixth
week of gestation and canalises from the sixth month. About two per cent of babies
will have symptomatic blockage of the nasolacrimal duct.

How Do I Treat Blocked Tear Ducts?

The usual treatment in cases which are not infected is to massage the lacrimal sac
(see below). Massage of the lacrimal sac has been shown to result in a higher rate of
spontaneous cure when compared to "masterly inactivity". It is not necessary to treat
all cases of blocked tear ducts with antibiotics. Frank purulent conjunctivitis should be
treated with a short course of antibiotics such as chloramphenicol drops second hourly
for three days. Chloramphenicol should not be used as a long term treatment even
Paediatric Ophthalmology Notes 2004                                                Page 20

though the risk of bone marrow suppression is rare.

Most cases of nasolacrimal duct obstruction resolve spontaneously by six to nine
months of age so it is usual practice to wait until age one year before probing. In a
child with recurrent infections or where epiphora is particularly troublesome, probing is
indicated at an earlier age. If the child's eyes are still watering after twelve months of
age, probing is almost always necessary as there is almost no spontaneous resolution
after age one year.

Teaching the Technique of Lacrimal Sac Massage to the Parent

The technique of lacrimal sac massage should be taught to the parent for several
reasons; the spontaneous regression rate is higher when massage is used, the
likelihood of infection in the tear sac is probably reduced if the sac is periodically
emptied and lastly it gives the mother something to do as the doctor demonstrates
`masterly inactivity' while awaiting a spontaneous cure. Advising the mother to rub the
side of the bridge of the nose will achieve the last aim but demonstrates ignorance of
anatomy!

The mother should be shown (on herself), where to find the lacrimal crest (the sharp
edged buttress of bone at the nasal end of the inferior orbital margin) behind which is
found the lacrimal sac. Make sure that the mother's fingernail is short. The index
finger is passed posteriorly over the lacrimal crest. Pressure is then applied nasally
and inferiorly with a sideways rocking motion. The sac itself is not normally palpable.
If the sac is full of mucopus, the contents will be regurgitated back into the conjunctival
sac where they can be wiped away. Massage once or twice a day is all that is
necessary. Advise the parent to wash the finger carefully after massaging the lacrimal
sac to avoid the development of paronychia.

Probing of the Nasolacrimal Duct

Probing is usually carried out under a general anaesthetic. Either a blunt silver probe
or a blunt cannula is passed gently down the nasolacrimal duct and through the
obstruction. Many ophthalmologists confirm that they are in the nasal cavity by
syringing some fluorescein dye into the nose where it can be recovered into a suction
cannula by the anaesthetist. The success rate of probing is of the order of 70% so a
second probing may be necessary. Should a simple probing not work then the usual
procedure is to fracture the inferior turbinate bone into the nasal cavity and insert
some silicone tubes which then stay in place for up to six months. In recalcitrant
cases a dacryocystorhinostomy may become necessary. This is a major procedure in
small children. With the advent of silicone tube intubation, the indications for
dacryocystorhinostomy in children have been markedly reduced.

Amnniotocoele (Mucocoele) of the lacrimal sac
Paediatric Ophthalmology Notes 2004                                               Page 21


This is an uncommon condition which presents in the neonatal period with a blue
swelling of the lacrimal sac often extending onto the side of the nose. This condition is
always associated with blockage of the nasolacrimal duct and the mucocele may
extend down into the nasal cavity and produce nasal obstruction. Simple massage
again may cure this condition but dacryocystitis quite commonly develops and requires
surgical drainage. Probing then becomes necessary once the infection has settled
down.

Differential Diagnosis

Blockage of the nasolacrimal duct is not the only cause of watering eyes in infancy.
Do not forget to exclude corneal disease such as a corneal foreign body or ulcer.
Congenital glaucoma also occasionally presents as a watering eye. This is often
associated with photophobia. An eye with congenital glaucoma often has an enlarged
cornea with a ground glass appearance.

The possibility of ophthalmia neonatorum should be considered in any neonate with a
purulent discharge from the eyes.


TRAUMA

Major trauma is particularly devastating to the eye of a child; not only will there be
damage to vital structures but even with successful repair, the damage to the eye may
be such that the potential for normal visual development is lost.

A. Penetrating injuries

Children's eyes are frequently damaged by sharp objects such as pencils, scissors,
darts or high velocity objects such as BB pellets.

The child with a penetrating injury will usually be in considerable distress. Accordingly,
the correct diagnosis of a penetrating injury is often complicated by non compliance on
the part of the child. If a penetrating injury is suspected and co-operation is not
forthcoming, examination under general anaesthetic may be necessary. This is best
carried out in a hospital where the expertise and equipment are available to proceed to
definitive repair if a penetrating injury is discovered.

The cardinal sign of a penetrating injury is disruption of the coats of the eye. This is
usually associated with prolapse of intraocular contents. In the case of a penetrating
injury involving the cornea, there will usually be iris prolapse which will almost always
result in a peaked pupil with a prolapsed iris at the apex of the `peak'. The penetration
site from a sharp object such as a dart may not be obvious on superficial examination.
Paediatric Ophthalmology Notes 2004                                                  Page 22


Immediate referral to a centre equipped to deal with major eye trauma is called for.
The eye should be covered by a shield or a non compressive pad. Never instill
ointment into eyes with penetrating injuries. Sedation, as well as anti-emetics, may be
called for during transport. If there is likely to be a delay in obtaining definitive closure
of a perforated globe, parenteral antibiotics should be considered.
Penetrating injuries of the eyelids caused by objects such as pencils or scissors
sometimes cause penetrating eye injuries or even penetration of the orbital roof with
brain damage. Secondary injuries to the eye and orbit should always be excluded
when examining a child with a penetrating injury to the eyelids.

B. Blunt injuries

These are common in childhood. They are usually the result of injury during sports
such as squash, tennis, cricket, or from blunt objects such as stones. The rapid rise in
pressure in the anterior chamber from a blunt injury may cause tearing of the ciliary
body and anterior chamber angle structures. The result is bleeding in to the anterior
chamber which, if macroscopic, can be recognised as a hyphaema. Bed rest in
hospital is indicated to minimise the risk of a disastrous secondary haemorrhage.

The posterior structures of the eye may also be injured by blunt trauma; this can result
in retinal oedema or a choroidal rupture.

C. Non-Accidental Injury (NAI)

The possibility of NAI should always be considered when confronted by eye trauma,
particularly if the history and the signs are inconsistent with one another. Cigarette
burns to the lids, periorbital haemorrhage (black eye) and widespread retinal
haemorrhages in particular should raise suspicion. The ophthalmic manifestations of
child abuse are numerous; in addition to the commoner signs mentioned above they
include retinal detachment, cataract, dislocated lenses, traumatic mydriasis,
papilloedema, squint, corneal opacity and optic atrophy.

D. Chemical Burns

Burns with alkalis are potentially destructive of an eye and are a true ophthalmic
emergency. Unfortunately they are amongst the commonest chemicals which are
accidentally spilled into the eye. Alkalis readily penetrate the cornea, resulting in
serious intraocular injury which can lead to corneal necrosis and melting, glaucoma
and cataract. Acids are usually precipitated near the ocular surface and by and large
do not have the same deleterious effects as alkalis.

The treatment of chemical burns is immediate copious irrigation of the eye with water
or sterile saline. Local anaesthesia may be necessary to permit irrigation which should
Paediatric Ophthalmology Notes 2004                                                 Page 23

be carried out for at least 10 or 20 minutes. In the case of lime burns the conjunctival
fornices should be swept clear of any particulate alkali. Ophthalmic advice should
always be sought.


SOME SERIOUS EYE CONDITIONS REQUIRING IMMEDIATE REFERRAL

        Don't forget : RARE DISEASES PRESENT TO COMMON DOCTORS

A. Leukocoria

Leukocoria is an uncommon condition, with a large differential diagnosis, which almost
always indicates severe eye disease. The general practitioner has a crucial role in
obtaining an early diagnosis which may, in some cases, prove to be life saving.
Mothers frequently notice an `abnormal' appearance to the pupil or eye (in real life or
in photographs) before a white pupil is obvious to the doctor. Ignore this complaint at
your professional peril.

B. Retinoblastoma

This is the commonest intraocular malignancy in childhood. It usually presents within
the first three years of life with a white pupil or `cats eye' reflex. The tumour assumes
several forms within the eye but it usually looks like a whitish mass on the retina. The
other common presenting sign is a squint, caused by loss of the fixation reflex when
the macula is involved by the tumour. Most cases arise as new mutations. If both
eyes are involved or if the disease is multifocal in one eye, it may be assumed that the
disease has arisen as a result of a germinal mutation. In these cases, the tumour will
be subsequently transmitted as an autosomal dominant condition with greater than
80% penetrance to the patient's children. In 6 - 8% of patients there will be a positive
family history. Within affected families, the identification of carriers of the gene in
newborns is now standard practice. Gene carriers have a long term risk of a second
malignancy such as an osteogenic sarcoma.

If the diagnosis of retinoblastoma is suspected, urgent referral to an ophthalmologist
versed in the management of retinoblastoma is indicated. Treatment undertaken at
an early stage is life saving. After confirmation of the diagnosis, management usually
involves chemotherapy to shrink the tumour followed by laser or cryotherapy to the
residual tumour if there is visual potential or enucleation of the affected eye if the sight
cannot be saved. Laser or cryotherapy alone can be used for small tumours or local
recurrences. Local irradiation is now rarely used because of long term complications.

C. Congenital Cataract

This is the most common cause of leukocoria. It may be unilateral or bilateral. The
Paediatric Ophthalmology Notes 2004                                                Page 24

aetiology of congenital cataracts can be either hereditary, infectious (eg rubella),
metabolic (eg galactosaemia) or associated with a syndrome (eg Down syndrome).
The trend towards early diagnosis and treatment in paediatric ophthalmology is
nowhere better illustrated than in the case of congenital cataract. Vitrectomy
instruments, developed for use in retinal detachment surgery, have revolutionised
congenital cataract surgery. Aggressive early surgery (by age six weeks) together with
advances in contact lens technology have changed the outlook for the child with
congenital cataract. Seventy percent of children with bilateral congenital cataracts will
achieve a final vision of 6/18 or better. Even unilateral cataract, which causes severe
amblyopia if untreated, has a 50% chance of good vision if treated by three months of
age. Good visual results are, however, by no means universal after congenital
cataract surgery. The fitting and maintenance of the contact lenses is extraordinarily
time consuming, expensive and often frustrating for the parents. Nonetheless, the cost
of intervention, with its prospect of useful vision, when measured against the economic
loss to the individual and the community of blindness from birth, pales into
insignificance. The prevention of the tragedy of the congenital rubella syndrome by
immunisation lies firmly within the province of the family doctor. Congenital cataract
should be excluded in all newborn children by confirming the presence of a normal red
fundus reflex in both eyes (use a direct ophthalmoscope at arms length in a darkened
room) prior to discharge home. Early treatment (before three months of age) of
congenital cataract gets results-late treatment is doomed to failure because of the
development of deprivation amblyopia and sensory deprivation nystagmus.

Any child who has had cataract surgery in infancy must have whole of life follow-up
because of the long term risk of glaucoma (30%) and retinal detachment.

Intraocular lenses are not used in babies firstly, because the refractive power of the
eye changes dramatically in the first three years of life with growth of the eye and,
secondly, and because of the significant post operative opacification in the posterior
lens capsule which necessitates a prophylactic posterior capsulotomy and anterior
vitrectomy. Secondary intraocular lens implantation is usually done for congenital
cataracts around age four when the future growth of the eye can be reliably predicted.

D. Congenital and Infantile Glaucoma

This is a form of glaucoma which usually has its onset in the first three years of life. It
may be present at birth and can involve one or both eyes. The presenting symptoms
are epiphora (tearing) and photophobia. Because the infant eye is distensible, the
corneal diameter increases giving the `ox-eye' appearance (buphthalmos). Any child
with a corneal diameter greater than 12mm has glaucoma until proven otherwise. As
a result of corneal enlargement, tears may develop in Descemet's membrane, leading
to corneal oedema which produces a `ground glass' appearance. The disease may
occur in isolation or as part of a syndrome eg Sturge-Weber syndrome.
Paediatric Ophthalmology Notes 2004                                               Page 25

The treatment of congenital glaucoma is almost always surgical, usually by opening an
abnormal trabecular meshwork by goniotomy or trabeculotomy. Approximately 80% of
patients will be cured by surgery.


PARTICULAR PROBLEMS IN THE OLDER CHILD AND ADOLESCENT

Refractive errors are important causes of visual discomfort in this age group. They
should be suspected if the adolescent complains of headaches brought on by visual
effort or if reading vision is better than distance vision. Myopia often has its onset in
late childhood or early adolescence. Phorias (latent squints) are common causes of
eye strain in this age group. Refractive errors and squints can always be diagnosed, if
present, in this age group but before ascribing school problems to them a thorough
assessment of the patients psychological state should also be made.

There appears to be a “myopia epidemic” occurring worldwide at present, but
predominantly in Asian countries where up to 90% of school leavers are myopic. This
is a significant public health issue as myopia can lead to visual impairment through
retinal detachment, glaucoma and myopic maculopathy. The cause appears to be a
combination of genetic and environmental factors. While lacking a strong evidence
base, it is probably prudent to recommend that children do not undertake near work
for more than 30 minutes without a rest, that they do not read in the dark, and that
they get lots of outdoor exercise.


CHILDREN AT HIGH RISK OF EYE PATHOLOGY

Certain children are at high risk of ocular pathology; for instance, almost any condition
which results in cerebral dysfunction can produce a squint. Children with cerebral
palsy and Down syndrome fall into this category.

Premature babies are at high risk of visual dysfunction. Not only do very small babies
face the risk of retinopathy of prematurity (old name - retrolental fibroplasia) but these
children subsequently have a higher incidence of both squint and refractive errors and
deserve close supervision during childhood.

All infants require their red reflex to be checked day one of life.


SOME DISORDERS OF THE ORBIT AND EYELIDS IN CHILDHOOD

A. Preseptal (Periorbital) Cellulitis

Preseptal cellulitis is an infection in the space between the orbital septum and the skin
Paediatric Ophthalmology Notes 2004                                                 Page 26

of the eyelid.

This is a not uncommon entity usually seen in the under five year old. There is often
an antecedent respiratory tract infection. Spread to the preseptal space (ie on front of
the orbital septum but behind the skin of the eyelid) is usually haematogenous but
infection in this space following trauma or complicating external ocular infection can
occur. There is a well demarcated pink or purplish swelling of the lids which are very
oedematous. There are no signs, such as proptosis or reduced ocular motility,
indicating involvement of intra orbital structures. Affected children are usually febrile
and may be severely ill.

The pathogens are usually Staph aureus or respiratory pathogens such as
Haemophilus influenzae or Strep pyogenes. Blood cultures should always be
obtained before starting treatment with intravenous antibiotics. HiB vaccination is
reducing the incidence and severity of this disorder.

B. Orbital Cellulitis

Orbital cellulitis refers to severe inflammation (usually due to infection) within the orbit
and is a medical emergency which should be cared for by the ophthalmologists, the
ENT surgeons and the paediatricians.

True orbital cellulitis is less common than preseptal cellulitis and is usually seen in
children older than five years. The onset is acute. The cardinal signs are pain on eye
movement with limited ocular motility, proptosis or globe displacement, and
conjunctival redness or chemosis. Most cases are caused by spread from infected
sinuses. Vision may be lost due to optic neuropathy.

Culture from the conjunctiva is often misleading. Blood cultures are seldom useful.
MRI or CT scanning of the orbit and sinuses should be undertaken in all cases of
orbital cellulitis and in cases of preseptal cellulitis where there is doubt whether
infection is contained in the preseptal space.

Children with orbital cellulitis run the risk of developing cavernous sinus thrombosis,
meningitis, brain abscess or septicaemia. Both preseptal and orbital cellulitis are
potentially life threatening and parenteral antibiotics are strongly recommended.
Topical antibiotics are useless as they do not penetrate into the soft tissue spaces
involved.

C. Ptosis

Ptosis in children is most commonly caused by a maldevelopment of the levator
muscle of the upper lid (congenital ptosis). Other causes can be classified under
myogenic (eg myasthenia gravis), neurogenic (eg third nerve palsy) or mechanical (eg
Paediatric Ophthalmology Notes 2004                                               Page 27

plexiform neuroma). Congenital ptosis is usually a cosmetic problem and is usually
corrected surgically before entry into preschool. The ptotic lid can, however, induce
astigmatism which often produces amblyopia so ophthalmic assessment is
recommended when the diagnosis is made in infancy. If the lid is so ptotic that it
covers the pupil urgent surgery is indicated.

D. Proptosis

Proptosis in children is rare. The majority of cases of slowly developing proptosis are
due to an intraorbital dermoid cyst.

Rapidly developing proptosis in a child should always raise the possibility of
rhabdomyosarcoma although acute bleeding into a lymphangioma (chocolate cyst) is
also a common cause. There is a large differential diagnosis of orbital tumours in
children. The removal of all but superficial orbital tumours such as external angular
dermoids is now usually undertaken by ophthalmologists with subspecialty training in
orbital surgery. Complex cases may require a combined approach involving, for
instance, ophthalmologists, neurosurgeons and craniofacial surgeons.



NEW ISSUES IN CHILDHOOD BLINDNESS

Globally there are estimated to be 1.4 million children blind (VA in better eye of <3/60).
Blindness is more common in children from poorer countries because of diseases
such as measles, vitamin A deficiency, ophthalmia neonatorum, malaria and trachoma
and there are fewer trained people and resources to manage eye disease. Vision
20/20 has targeted reducing
The prevalence of childhood blindness by eliminating corneal scarring due to measles,
vitamin A deficiency and ophthalmia neonatorum; eliminating congenital rubella
syndrome; providing appropriate treatment to children with congenital cataract;
screening for babies at risk of ROP and providing treatment; and providing a simple
screening exam for school age children.


LEARNING DISABILITIES AND THE VISUAL SYSTEM

The subject of learning disabilities and their relationship to disorders of the visual
system is a controversial one. There is no validly conducted scientific research which
shows a causal relationship between minor disorders of the visual system and learning
disabilities.

Learning disabilities in children, however they are defined, probably affect 10 - 15% of
the school population. The parents are frequently desperate and seek advice from a
Paediatric Ophthalmology Notes 2004                                                Page 28

wide variety of professional groups down to taking advice from outright quacks.
Ophthalmologists often see children with learning disabilities to determine whether or
not ocular pathology is present. At the outset let it be said that there is no evidence
that there is a higher incidence of disorders of the anterior visual pathway such as
refractive errors or squints in children with learning disabilities than there is in the
general population. Ocular abnormalities such as refractive errors and squints, when
present, should of course be treated in children with learning disabilities as they would
be in normal children. Very few children require reading glasses as powers of
accommodation in children with normal eyes are more than adequate for normal
reading tasks.

Dyslexia

Dyslexia is a specific type of learning disorder that manifests as an idiopathic difficulty
in reading by persons with otherwise normal intelligence, conventional instruction and
socio-cultural opportunity. There is no generally accepted test used to diagnose
children with dyslexia but a widely accepted definition would be a child whose reading
age is two years behind his or her chronological age. It is important to note that the
above mentioned definition does include normal intelligence (which should be tested),
conventional instruction (about which enquiries should be made) and adequate socio-
cultural opportunity. The roots of poor school performance may lie in a culturally or
economically deprived home environment. Unravelling these extraneous factors in a
child with school failure should be part of the child's assessment. Enough data is now
available to us eg from autopsy studies to indicate that dyslexic persons do in fact
have demonstrable structural abnormalities in the CNS particularly in the angular
gyrus of the dominant cerebral hemisphere. There is often a family history of learning
disabilities. Males are more commonly affected than females.
A broad-based consensus of educators, psychologists, and medical specialists
recommend that individuals with dyslexia or related learning disabilities should receive
(1) early comprehensive educational, psychological, and medical assessment; and (2)
education remediation combined with appropriate psychological and medical
treatment.
Multi disciplinary evaluation and management must be based on proven procedures
demonstrated by valid research.

There is no single best treatment for children with dyslexia.           After appropriate
assessment, remedial teaching appears to offer the best results.

"Developmental" Optometry

"Developmental" optometrists are a subgroup of optometrists who profess, amongst
other things, expertise in the management of children with learning disabilities.
Parents with children who consult "developmental" optometrists are usually provided
with a detailed assessment sheet couched in pseudo scientific language (which may
Paediatric Ophthalmology Notes 2004                                                   Page 29

either impress or terrify the parents or both) listing their child's visual abnormalities.

Almost invariably a series of (often expensive) exercises as well as reading glasses to
relieve "accommodative" stress are prescribed. The proponents of "developmental"
optometry are enthusiastic and almost religiose in their beliefs regarding the efficacy of
their treatments. Scientifically valid studies supporting such treatments are yet to
appear in the literature. There is no doubt a significant placebo effect is at work in the
nostrums of "developmental" optometrists. Many (?most) main stream ethical
optometrists are sceptical regarding the claims of "developmental" optometry. Perhaps
it is the time spent with and attention to the child that is beneficial?

Tinted Lenses

Children with dyslexia often report instability of visual images and a swimming
sensation when viewing small print. In 1983, tinted (Irlen) lenses burst on to the scene
and were declared to be a "cure" for dyslexia. The Irlen assessment process and the
prescription of tinted lenses are expensive and the entire procedure is a commercial
secret. The Irlen lens technique has never been properly validated. Indeed, there is
evidence that tinted lenses work no better than placebo.

Quack Therapies

The parents of children with learning disabilities need to be made aware of the long
history of quack therapies for children with learning disabilities. Sensation claims of
breakthrough treatments based on hitherto unknown assessment and treatment
procedures and unsupported by controlled clinical trials are the hallmarks of quack
therapies.

Treatment

Proper assessment should be performed by, for instance, Paediatricians, Guidance
officers and Psychologists so that the child's deficiencies and strengths can be
discovered. An individual program of remediation should be planned for the child.
Paediatric Ophthalmology Notes 2004                                                 Page 30


                             Table 1 Squint Terminology;


Fusion:        The cortical integration of the images received by the two eyes. This is
               only possible if the two eyes are correctly aligned. In its highest form this
               results in stereopsis, or depth perception.

Eso-:          convergent deviation

Exo-:          divergent deviation

Hyper-:        vertical deviation (left or right used with this term denotes the higher eye)

-tropia:       constant deviation of the eyes.

-phoria:       a latent deviation of the eyes, brought out when fusion is interrupted e.g.
               by the cover test. e.g. left esotropia = a convergent squint present
               constantly in the left eye.

Alternating:   a squint occurring for an equal amount of time in each eye.

Manifest Squint:      a constant squint.

Comitant squint:      the angle is constant in all directions.

Noncomitant / Incomitant squint: the angle varies in different positions of gaze e.g.
sixth nerve palsy.
Paediatric Ophthalmology Notes 2004                                              Page 31


                          Table 2: Refraction Terminology

Accommodation:       The adjustment of the focus of the eye for different distances to
                     enable a sharp image to be formed on the retina. This is carved
                     out by changing the shape of the lens via contraction of the ciliary
                     body.

Anisometropia:       A difference in the refractive error of the two eyes.

Emmetropia:          Light rays from infinity (ie parallel) are brought to a focus on the
                     retina without the use of accommodation.

Hypermetropia:       (Long sightedness) is present if the focal point of light rays from
                     infinity is behind the retina.         In this refractive state
                     accommodation is necessary to bring light rays from infinity to a
                     focus of the retina. Mild hypermetropia is the rule in infancy and
                     early childhood.

Myopia:              (short-sightedness) is present when light rays from infinity come
                     to a focus in front of the retina. Light rays from near objects are
                     divergent so they will come to a focus on the retina of a myopic
                     eye without the need for accommodation. Light rays from distant
                     objects can only be focussed on the retina with help of glasses or
                     contact lenses containing concave (diverging) lenses.

Astigmatism:         A refractive error which prevents light rays from coming to a
                     single focus on the retina because the light rays are refracted
                     differently by different meridians of the cornea. An astigmatic
                     surface can best be conceptualised like the back surface of a
                     spoon; curved more in one plane than another. I tell parents of
                     children with astigmatism that the front of their child‟s eye is
                     shaped like a football and not a soccer ball. Astigmatism is very
                     common in the first year of life.
Paediatric Ophthalmology Notes 2004                                           Page 32


                                  Table 3 Summary

PRACTICAL HINTS

SQUINT

      All children should fix and follow an object by three months of age
      A constant squint at any age requires treatment
      In any squint exclude intraocular pathology by a dilated fundus examination.
      Pupil dilatation using cyclopentolate or tropicamide is completely safe in
       children
      Most children with a vertical squint present with a face turn, a head tilt or
       apparent `torticollis'. The squint itself may not be obvious.


WHEN TO REFER A CHILD TO AN OPHTHALMOLOGIST

      A child with squint or nystagmus, at any age
      Any sight threatening condition
      If unsure about diagnosis or management
      When encountering an uncommon condition for the first time
      Any child with a white pupil noticed by yourself or complained of by the parent
       (urgent)

NB:
      More mistakes are made by not looking than by not knowing!
      Rare diseases usually present to common doctors
      If unsure, you can always pick up the telephone from anywhere in NZ to ask for
       advice!


Websites to visit:
www.ranzco.edu (Royal Australian and New Zealand College of Ophthalmologists)
www.aao.org (American Academy of Ophthalmology)
www.aapos.org (American Association for Pediatric Ophthalmology and Strabismus)
www.rcophth.ac.uk (Royal college of Ophthalmologists, London)

Each teaching hospital library has a good collection of textbooks for you to consult.
Suggestions for purchase are always welcome.