Peripheral Retinal Degenerations
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Contents
Classification
- Intra-retinal Degenerations: microcystoid degenerations (Typical & Reticular), senile retinoschisis, pars plana cysts
- Retino-vitreal degenerations: Lattice degeneration, Snail-track degeneration, White with & without pressure
- 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
References
- Engstrom RE, Glasgow BJ, Foos RY, Straatsma BR. Degenerative Diseases of the Peripheral Retina. Duane's Ophthalmology. Chapter 26. 2006 Edition.
- Lewis H. Peripheral retinal degenerations and the risk of retinal detachment. Am J Ophthalmol. 2003 Jul;136(1):155-60.