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.
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