Peripheral Retinal Degenerations

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Contents

Classification

1. Intra-retinal Degenerations : microcystoid degenerations (Typical & Reticular), senile retinoschisis, pars plana cysts

2. Retino-vitreal degenerations : Lattice degeneration, Snail-track degeneration, White with & without pressure

3. Chorioretinal degenerations : Paving stone degeneration

Intra-Retinal Degenerations

Microcystoid degeneration

Most frequent degenerative lesion of the area - Characterized by small bubbles or vacuoles in the peripheral retina near ora - These occur in the outer plexiform and inner nuclear layers of retina - Mostly symmetrical, more in temporal retina than nasal, more superiorly than inferiorly - Inner wall of a cyst may be absent giving impression of that of a retinal hole which is actually a pseudo-hole - Does not predispose to retinal detachment - A second type of degeneration called Reticular Cystoid Degeneration has been seen in eyes of cadavers. These are histologically different and more posterior compared to regular cystoid.

Senile Retinoschisis

Occurs in about 2 – 4% of population above 40 years of age - Lesion appears like a bullous elevation of peripheral retina and lies mainly in the temporal segment specially infero-temporal segment - It is the result of extension of microcystoid degeneration and similar pathogenic factors can be considered like traction by zonular fibres and poor peripheral vascularization - No vitreous alteration specific to this lesion - Mostly asymptomatic - It remains immobile with movement of eyeball and produces an absolute field defect (to differentiate from bullous RD) - It may enlarge to involve posterior pole or may lead to Retinal detachment especially if a break is present in either/both walls

Pars Plana Cysts

Clear bullous elevation of non-pigmented ciliary epithelium of pars plana - Usually more prominent temporally underneath the vitreous base - Content is usually clear and has been found to contain hyaluronic acid - In patients with abnormal serum proteins, like in multiple myeloma, the cysts may contain abnormal protein, giving them a turbid appearance - Seen in 5 – 10 % of all eyes examined - Bilateral in one third cases and show no sex predilection - These are harmless lesions not associated with serious eye complications

Retino-Vitreal Degenerations

Lattice Degeneration

Snail track degeneration

Characterized by groups of glistening white dots (which have been compared to frost granules or salt) - Occurs mainly in young and myopic eye - Frequency does not increase with age - Always found in the area of the equator or just in front of it - Histologically, this lesion consist of degeneration of the neural elements of retina leading to an atrophy of the tissues with lipid deposits in the internal retinal layers - Many authors consider it to be early stage of lattice degeneration - It may lead to development of a retinal break and also RD. In many studies the incidence of RD as a complication has been reported to be between 10 to 20 %. - Prophylactic intervention for this lesion has been debated

White With Pressure

Distinctive milky white or opalescent appearance of the peripheral retina that is observed in many normal eyes when examined with scleral depression - Retina appears normal without depression - It is common and seen in around 30 to 35% of eyes examined with scleral depression - Infero-nasal quadrant least likely to be affected - Incidence increases with age , no sex predilection - Benign condition not associated with retinal breaks - Must be carefully distinguished from a subclinical peripheral RD

White Without Pressure

Distinctive white appearance of the peripheral retina without indentation - Whiter than the retina in white with pressure and the choroidal markings are almost obscured - Whiteness further accentuated if scleral depression done - Margins are sharply demarcated from normal retina - Intervening patches of normal retina should not be confused with retinal holes - Exact cause is unknown , one school of thought states it to be a manifestation of peripheral vitreous traction while one believes it to be simply an abnormal reflex from a structurally normal VR interface - Frequently causes confusion with subclinical RD and Retinoschisis but indentation clearly reveals that retina is still apposed to the RPE.


Chorioretinal Degenerations

Paving Stone Degeneration

Has a dramatic appearance, revealing multiple rounded punched-out areas of choroidal and retinal atrophy - Located between ora and equator with size of one to several disc diameters - More common in infero-nasal and temporal quadrants - Lesions are yellow-white in color with due to sclera being partly visible through the atrophic choroid - Large choroidal vessels seen running through the base - Lesions have discrete margins which may be pigmented - May become confluent - Frequently bilateral, no sexual predilection, increasingly common with age - Benign lesions not associated with complications

Diffuse pigmentary disseminations

c) Diffuse peripheral atrophy

Original article contributed by: Dr Jay Chhablani, User:Dr. Anupam Basant Bagdi MBBS
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