The peripheral retina extends from equator to ora serrata , comprises of extensive degenerative changes and anatomical variations with clinical importance in certain situations indicating the importance of meticulous examination of peripheral retina with indirect ophthalmoscopy. Anatomically, peripheral retinal degenerations can be categorized in the following ways :

Vitreo-retinal degenerations :

1. Lattice degeneration
2. Snail track degeneration
3. Snowflake degeneration
4. White without pressure ( WWOP)

Intraretinal degenerations :

1. Microcystoid degeneration (Typical and reticular)
2. Degenerative Retinoschisis
3. Pars plana cyst

Chorioretinal degenerations :

1. Paving stone degenerations

Tips for peripheral Fundus examination :

The patient is asked to lie in the supine position and indirect ophthalmoscope mounted on the examiner’s head with a 20D condensing lens placed parallel to the iris plane. The patient is asked to look away from the examiner in the extreme periphery in the direction of the quadrant to be examined and direct the light in the same quadrant in order to adapt the light and prevent photophobia in case the light is focused at the macula initially during the examination. Once the lesion is visualized, the scleral indentation should be attempted and the patient is asked to look down if superior quadrant to be seen and indenter is placed at the orbital rim outside the upper lid and the patient is asked to look up slowly and indenter is gradually advanced with gentle pressure for optimal indentation. Indenter should be tangential to the globe and not perpendicular to avoid pain. Similarly, the rest of the peripheral fundus to be examined and macula to be visualized at last to complete the fundus evaluation with the patient being comfortable.

Lattice degeneration :

Ophthalmoscopically, seen as one or more bands of retinal thinning, sometimes with an arborizing network of white lines and pigmentary disturbances within the thinned out retina. It is the most important peripheral degeneration that predisposes to retinal detachment. Bilateral in one-third to one-half of affected patients with a familial predilection. More frequently seen in myopes and commonly seen in superior quadrant than inferior; less common in horizontal meridians. Associated with retinal holes or atrophic holes.

Microcystoid degeneration :

Typical microcystic degeneration of the retina appears as a cluster of tiny vesicles or vacuole on a greyish white background and is almost universal over the age of 20 years. It involves the middle and outer retina, limited by the inner plexiform layer. Mostly symmetrical in distribution, rarely retinal holes may form but not related to retinal detachment. It is believed to be involved in the pathogenesis of senile retinoschisis.

Reticular cystoid degeneration is characterized by subsurface arborizing vascular pattern (reticular) usually located posterior to typical cystoid degeneration and free borders are limited by fine vessels. Found in approximately 20% of the adult population and typically involves the inner retina.

Degenerative retinoschisis :

Degenerative retinoschisis is usually bilateral, often symmetrical, and most commonly seen in inferotemporal quadrant; slowly progressive. It can exist in two forms – Typical and reticular (less common). In typical retinoschisis, split is in the outer plexiform layer while in reticular form, splitting occurs at the level of the nerve fiber layer. It is usually characterized by dome-shaped elevation of the inner retinal layer, immobile and without surface corrugations. Retinoschisis causes an absolute scotoma ( vs relative scotoma in retinal detachment). Rarely can result in retinal detachment and treatment is warranted when the retinal detachment is progressive and threatening the macula.

Differentiation with RD:

1. Retinoschisis is generally associated with (surrounded all sides by) microcystoid degeneration and absence of surface corrugations, unlike RD.
2. In kinetic echography RD is mobile but schisis is not mobile and with indentation, schitic cavity will not collapse on ultrasound unlike RD as there is no subretinal fluid to displace
3. When the progression of the schisis toward the posterior pole extends posterior to the equator, perimetry reveals an absolute field defect, whereas the defect associated with retinal detachment is relative.
4. Intraretinal cavity of schisis is optically empty
5. In a test burn with argon laser, schisis uptakes the burn but RD does not .

Snail track degeneration :

It is characterized by sharply demarcated bands of white, frost-like change of the inner retina mimicking reminiscent of the tracks made by a snail – elongated lesions, often bilateral commonly seen in superotemporal quadrant and affects the myopic eyes of young individuals with a risk of retinal detachment. Prophylactic treatment is debatable.

Vitreoretinal tufts:

It is clinically described as a small, discrete, well-circumscribed, elevated vitreoretinal lesion with strong vitreous adhesion and histologically comprises of neuroglial cells within the tuft. Usually, single, unilateral and congenital lesions are associated with retinal tears or hole formation leading to retinal detachment. It can be classified as – cystic and zonular tractional tufts.

White with Pressure

Clinically evident as a greyish white appearance of the peripheral retina with a well-demarcated border associated with vitreous traction or adhesion to the overlying retina. Exact etiology is not known but speculative of optical phenomenon whereas vitreous traction or tension on vessels in these areas resulting in diminished blood flow and blanching of the area is another hypothesis to the retinal whitening.

Paving stone degeneration:

Paving stone degeneration appears as well delineated, depigmented punched out areas with irregular pigmentation at the margin of the lesions in the peripheral retina anterior to the equator and most commonly seen in the inferior quadrant. It is usually bilateral, slowly progressive and frequently evident in older patients. Due to outer retinal atrophy, choroidal vessels are seen traversing the lesions at the base.

Meridional folds:

A meridional fold appears as a radially oriented elevation of the peripheral retina in alignment with a dentate process or an ora bay and may be associated with retinal breaks. Infrequently, a meridional fold aligned with a dentate process may extend up to the ciliary process to form a meridional complex. Folds are more commonly seen in the nasal retina – mostly superonasal quadrant and often occurs with symmetrical mirror folds in the corresponding clock hour of opposite eyes.

Peripheral retinal degenerations predisposing to Retinal Detachment

1. Lattice Degeneration
2. Snail track Degeneration
3. White without pressure
4. Degenerative Retinoschisis
5. Tractional tufts

Peripheral retinal degenerations not predisposing to Retinal Detachment

1. Pavingstone Degeneration
2. Microcystoid Degeneration
3. Peripheral Drusen
4. Honeycomb Degeneration

Lesions like lattice degeneration, snail track degenerations, tractional tufts have a predisposition for retinal detachment but prophylactic treatment is still controversial except in high-risk situations such as fellow eye with retinal detachments, strong family history of retinal detachment and acute symptoms of posterior vitreous detachment.