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RETINAL DETACHMENT

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Common Eye Disease

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									RETINAL DETACHMENT
It is the separation of neurosensory retina proper
from the pigment epithelium. Normally these two
layers are loosely attached to each other with a
potential space in between. Hence, actually speaking
the term retinal detachment is a misnomer and it
should be retinal separation.
Classification
Clinico-etiologically retinal detachment can be
classified into three types:
1. Rhegmatogenous or primary retinal detachment.
2. Tractional retinal detachment Secondary
retinal
3. Exudative retinal detachment detachment
A
B
Fig. 11.26. Age-related macular degeneration: A,
nonexudative; B, exudative.
276 Comprehensive OPHTHALMOLOGY
RHEGMATOGENOUS OR PRIMARY RETINAL
DETACHMENT
It is usually associated with a retinal break (hole or
tear) through which subretinal fluid (SRF) seeps and
separates the sensory retina from the pigmentary
epithelium.
Etiology
It is still not clear exactly. The predisposing factors
and the proposed pathogenesis is as follows:
A. Predisposing factors include:
1. Age. The condition is most common in 40-60
years. However, age is no bar.
2. Sex. More common in males (M:F—3:2).
3. Myopia. About 40 percent cases of rhegmatogenous
retinal detachment are myopic.
4. Aphakia. The condition is more common in
aphakes than phakes.
5. Retinal degenerations predisposed to retinal
detachment are as follows:
  Lattice degeneration
  Snail track degeneration.
  White-with-pressure and white-without-or
occult pressure.
  Acquired retinoschisis.
  Focal pigment clumps.
6. Trauma. It may also act as a predisposing factor.
7. Senile posterior vitreous detachment (PVD). It
is associated with retinal detachment in many
cases.
B. Pathogenesis
Pathogenesis of rhegmatogenous retinal detachment
(RRD) is summarized in Figure 11.27. The retinal
breaks responsible for RRD are caused by the interplay
between the dynamic vitreoretinal traction and
predisposing degeneration in the peripheral retina.
Dynamic vitreoretinal traction is induced by rapid eye
movements especially in the presence of PVD,
vitreous synersis, aphakia and myopia. Once the
retinal break is formed, the liquified vitreous may seep
through it separating the sensory retina from the
pigment epithelium. As the subretinal fluid (SRF)
accumulates, it tends to gravitate downwards. The
final shape and position of RD is determined by
location of retinal break, and the anatomical limits of
optic disc and ora serrata.
Clinical features
Prodromal symptoms. These include dark spots
(floaters) in front of the eye (due to rapid vitreous
degeneration) and photopsia, i.e., sensation of flashes
of light (due to irritation of retina by vitreous
movements).
Symptoms of detached retina. These are as follows:
1. Localised relative loss in the field of vision (of
detached retina) is noticed by the patient in early
stage which progresses to a total loss when
peripheral detachment proceeds gradually towards
the macular area.
2. Sudden painless loss of vision occurs when the
detachment is large and central. Such patients
usually complain of sudden appearance of a dark
cloud or veil in front of the eye.
Signs. These are elicited on following examinations:
1. External examination, eye is usually normal.
2. Intraocular pressure is usually slightly lower or
may be normal.
3. Marcus Gunn pupil (relative afferent pupillary
defect) is present in eyes with extensive RD.
4. Plane mirror examination reveals an altered red
reflex in pupillary area (i.e., greyish reflex in the
quadrant of detached retina).
5. Ophthalmoscopy should be carried out both by
direct and indirect techniques. Retinal detachment
is best examined by indirect ophthalmoscopy
using scleral indentation (to enhance visualization
of the peripheral retina anterior to equator). On
examination, freshly-detached retina gives grey
reflex instead of normal pink reflex and is raised
anteriorly (convex configuration). It is thrown
Senile acute Predisposing Aphakia
posterior retinal (Endodonesis)
vitreous degenerations
detachment
(acute PVD)
.
Retinal break . Trauma
.
The degenerated fluid vitreous seeps through the retinal
break and collects as subretinal fluid (SRF) between
the sensory retina and pigmentary epithelium.
.
Retinal detachment
Fig. 11.27. Flow chart depicting pathogenesis of
rhegmatogenous retinal detachment.
DISEASES OF THE RETINA 277
Complications
These usually occur in long-standing cases and
include proliferative vitreoretinopathy (PVR),
complicated cataract, uveitis and phthisis bulbi.
Treatment
Basic principles and steps of RD surgery are:
1. Sealing of retinal breaks. All the retinal breaks
should be detected, accurately localised and sealed
by producing aseptic chorioretinitis, with
cryocoagulation, or photocoagulation or diathermy.
Cryocoagulation is more frequently utilised (Fig.
11.29).
2. SRF drainage. It allows immediate apposition
between sensory retina and RPE. SRF drainage is done
very carefully by inserting a fine needle through the
sclera and choroid into the subretinal space and
allowing SRF to drain away. SRF drainage may not be
required in some cases.
3. To maintain chorioretinal apposition for at least
a couple of weeks. This can be accomplished by either
of the following procedures depending upon the
clinical condition of the eye:
i. Scleral buckling i.e., inward indentation of sclera
to provide external temponade is still widely
used to achieve the above mentioned goal
successfully in simple cases of primary RD. Scleral
buckling is achieved by inserting an explant
(silicone sponge or solid silicone band) with the
help of mattress type sutures applied in the
sclera (Fig. 11.30). Radially oriented explant is
most effective in sealing an isolated hole, and
into folds which oscillate with the movements of
the eye. These may be small or may assume the
shape of balloons in large bullous retinal
detachment. In total detachment retina becomes
funnel-shaped, being attached only at the disc
and ora serrata. Retinal vessels appear as dark
tortuous cords oscillating with the movement of
detached retina. Retinal breaks associated with
rhegmatogenous detachment are located with
difficulty. These look reddish in colour and vary
in shape. These may be round, horse-shoe
shaped, slit-like or in the form of a large anterior
dialysis (Fig. 11.28). Retinal breaks are most
frequently found in the periphery (commonest in
the upper temporal quadrant). Associated retinal
degenerations, pigmentation and haemorrhages
may be discovered.
Old retinal detachment is characterized by
retinal thining (due to atrophy), formation of
subretinal demarcation line (high water markes)
due to proliferation of RPE cells at the junction
of flat detachment and formation of secondary
intraretinal cysts (in very old RD).
6. Visual field charting reveals scotomas
corresponding to the area of detached retina,
which are relative to begin with but become
absolute in long-standing cases.
7. Electroretinography (ERG) is subnormal or
absent.
8. Ultrasonography confirms the diagnosis. It is of
particular value in patients with hazy media
especially in the presence of dense cataracts.
Fig. 11.28. Retinal detachment associated with: A, horse-shoe tear; B,
round retinal hole; C, anterior dialysis.
278 Comprehensive OPHTHALMOLOGY
circumferential explant (encirclage) is indicated in
breaks involving three or more quadrants.
ii. Pneumatic retinopaxy is a simple outpatient
procedure which can be used to fix a fresh
superior RD with one or two small holes extending
over less than two clock hours in upper two
thirds of the peripheral retina. In this technique
after sealing the breaks with cryopaxy, an
expanding gas bubble (SF6 or C3F8) is injected in
the vitreous. Then proper postioning of the
patient is done so that the break is uppermost
and the gas bubble remains in contact with the
tear for 5-7 days.
iii. Parsplana vitrectomy, endolaser photocoagulation
and internal temponade. This procedure
is indicated in:
  All complicated primary RDs, and
  All tractional RDs.
  Presently, even in uncomplicated primary RDs
(where scleral buckling is successful), the
primary vitrectomy is being used with increased
frequency by the experts in a bid to provide
better resutls.
Main steps of this procedure are:
  Pars plana,3-port vitrectomy (see page 247) is
done to remove all membranes and vitreous
and to clean the edges of retinal breaks.
  Internal drainage of SRF through existing
retinal breaks using a fine needle or through a
posterior retinotomy is done.
  Flattening of the retina is done by injecting
silicone oil or perflurocarbon liquid.
  Endolaser is then applied around the area of
retinal tears and holes to create chorioretinal
adhesions.
  To temponade the retina internally either
silicone oil is left inside or is exchanged with
some long acting gas (air-silicone oil exchange).
Gases commonly used to temponade the retina
are sulphur hexafluoride (SF6) or
perfluoropropane (C3F8) (see page 247).
Prophylaxis
Occurrence of primary retinal detachment can be
prevented by timely application of laser
photocoagulation or cryotherapy in the areas of
retinal breaks and/or predisposing lesions like lattice
degeneration. Prophylactic measures are particularly
indicated in patients having associated high risk
factors like myopia, aphakia, retinal detachment in
the fellow eye or history of retinal detachment in the
family.
EXUDATIVE OR SOLID RETINAL DETACHMENT
It occurs due to the retina being pushed away by a
neoplasm or accumulation of fluid beneath the retina
following inflammatory or vascular lesions.
Fig. 11.30. Diagram depicting scleral buckling and subretinal
fluid (SRF) drainage.
Fig. 11.29. Cryocoagulation of the retinal hole area under
direct vision with indirect ophthalmoscopy.
DISEASES OF THE RETINA 279
Treatment
  Exudative retinal detachment due to transudate,
exudate and haemorrhage may undergo
spontaneous regression following absorption of
the fluid. Thus, the treatment should be for the
causative disease.
  Presence of intraocular tumours usually requires
enucleation.
TRACTIONAL RETINAL DETACHMENT
It occurs due to retina being mechanically pulled
away from its bed by the contraction of fibrous tissue
in the vitreous (vitreoretinal tractional bands).
Etiology
It is associated with the following conditions:
  Post-traumatic retraction of scar tissue especially
following penetrating injury.
  Proliferative diabetic retinopathy.
  Post-haemorrhagic retinitis proliferans.
  Retinopathy of prematurity.
  Plastic cyclitis.
  Sickle cell retinopathy.
 Proliferative retinopathy in Eales’ disease.
Clinical features
  Tractional retinal detachment (Fig. 11.32) is
charcterised by presence of vitreoretinal bands
with lesions of the causative disease.
  Retinal breaks are usually absent and
configuration of the detached area is concave.
  The highest elevation of the retina occurs at sites
of vitreoretinal traction.
  Retinal mobility is severely reduced and shifting
fluid is absent.
Treatment
It is difficult and requires pars plana vitrectomy to
cut the vitreoretinal tractional bands and internal
tamponade as described above. Prognosis in such
cases is usually not so good.

								
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