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What is Retinal detachment ?
Retinal detachment means separation of neurosensory retina from the pigmented epithelium layer. Basically the nerve fiber layer of retina and Retinal pigmented layer these two layers loosely attached to each other with potential space in between.
Retinal Detachment is a misnomer and we can also called retinal Separation.
Classification of retinal detachment
The classification type of a retinal detachment as below..
1. Rhegmatogenous or primary retinal detachment
2. Tractional retinal detachment
3. Exudative retinal detachment
(Tractional retinal detachment and exudative retinal detachment are the secondary retinal detachment.)
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.
Senile posterior vitreous detachment (PVD). It is associated with retinal detachment in many cases.
B. Pathogenesis
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, j.e., sensation of flashes of light (due to irritation of retina by vitreous movements).
Symptoms of detached retina
These are as follows: 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.
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: 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 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.
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.
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:
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.
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.
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:
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. Radially oriented explant is most effective in sealing an isolated hole, and circumferential explant (encirclage) is indicated in breaks involving three or more quadrants.
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 (SF, or C3F) 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.
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 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 (SF) or perfluoropropane (CF.).
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.
Etiology
Its common causes can be grouped as under:
1. Systemic diseases.
These include: toxaemia of pregnancy, renal hypertension, blood dyscrasias and polyarteritis nodosa.
2. Ocular diseases. These include:
• Inflammations such as Harada's disease, sympathetic ophthalmia. posterior scleritis, and orbital cellulitis.
• Vascular diseases such as central serous retinopathy and exudative retinopathy of Coats;
• Neoplasms e.g., malignant melanoma of choroid and retinoblastoma (exophytic type) Sudden hypotony due to perforation of globe and intraocular operations.
Clinical features
Exudative retinal detachment can be differentiated from a simple primary detachment by:
• Absence of photopsia, holes/tears, folds and undulations.
• The exudative detachment is smooth and convex. At the summit of a tumour it is usually rounded and fixed and may show pigmentary disturbances.
• Occasionally, pattern of retinal vessels may be disturbed due to presence of neovascularisation on the tumour summit.
• Shifting fluid characterised by changing position of the detached area with gravity is the hallmark of exudative retinal detachment.
• On transillumination test a simple detachment appears transparent while solid detachment is opaque.
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...
What is Tractional Retinal Detachment ?
It happens due to retina mechanically pulled away from its bed by the contraction of fibrous tissue in the vitreous (vitreoretinal tractional bands).
Causes of tractional retinal detachment
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 of tractional retinal detachment
• Tractional retinal detachment 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 of tractional retinal detachment
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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