Peripheral Retinal Degenerations

Dr Subham Sinha Roy
Published Online: April 5th, 2020 | Read Time: 13 minutes, 36 seconds

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.

Structures

Anatomical Considerations

Clinically

The thin inner wall

Composed of the internal limiting membrane, the nerve fiber layer, and retinal vessels

Show snowflakes, as well as sheathing or silver wiring of vessels & schisis cavity, may be bridged by torn white grey tissues. These represent the Müller fibers that traverse the schisis cavity.

The Intraretinal cavity

Optically empty

The irregular outer wall

It contains portions of the inner nuclear, outer plexiform, outer nuclear, external limiting, and rod and cone layers.

Beaten metal appearance

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.

Zonular Traction retinal tuft

Cystic retinal tuft

Usually single and unilateral

These are small pyramid-like projections of whitish retinal tissues into the vitreous cavity.

Found within vitreous base & zonular fibres are attached to its apex. MC: inferiorly and nasally

They almost always occur in vitreous base area.

Congenital

Congenital

A significant cause of small round hole at retinal periphery. Vitreous base in normal health supports these breaks but in case of surgical aphakia or other conditions leading to traction in zonules these holes may give rise to RD

Cystic retinal degeneration occurs at the base of the tufts.
Severe vitreous traction may avulse a cystic tuft leading to FTRH

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.

WHITE WITH PRESSURE

WHITE WITHOUT PRESSURE

Induced by indenting sclera

Without any scleral indentation

Sharp borders

Ill-defined borders

Found at the post border of LD, SD & outer layer of schisis

Found adjacent to ora

Frequently seen in normal eyes

Generally found in elderly people & Myopic

Not associated withretinal detachment

Giant retinal Tear & RD may develop at the posterior border

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.

DEGENERATION

LOCATION

APPEARANCE

RISK OF RD

FEATURE

LATTICE DEGENERATION

Located between the equator and posterior border of the vitreous base

Most commonly seen in superotemporal region

Arborizing network of tiny white lines within the thinning

which may be associated with

pigmentary disturbances with or without associated atrophic retinal holes

Seen in 20-30% eyes presenting with RD.

  • 6-8% gen. population.
  • MC in myopics.
  • M=F
  • B/L in 50%

SNAILTRACK DEGENERATION

Peripheral retina

Icelands of degeneration with white frost snail track like appearance. Icelands are sharply defined tightly packed with snowflake appearance. The icelands are longer than lattice.

Frequently associated with round holes – can lead to RD

Atrophic changes with vitreous traction play an important role in causation.

DEGENERATIVE RETINOSCHISIS

Starts in the inferotemporal quadrants then progresses circumferentially and finally affects the entire periphery

Splitting of sensory retina into :

àouter[ choroidal] layer

àInner [vitreous] layer

Splitting occurs at the:

Outer plexiform layer = Typical form

Nerve fibre Layer = Reticular form

Very rare

  • Found in 5% of gen population over 20 years of age
  • 70% in hyperopic eyes.
  • Asymptomatic
  • B/L 60-70%

PAVING STONE /COBBLESTONE DEGENERATION

Located between ora serrata and equator

Most common in inferior quadrant

Characterized by discrete yellow white patches of focal chorioretinal atrophy with irregular black pigmentation at the margin of lesion and red lines which corresponds to choroidal blood vessels may traverse them

Paving stone degeneration does not increase the risk of retinal detachment and does not require prophylactic therapy.

SNOWFLAKE DEGENERATION

Scattered diffusely in peripheral fundus

Multiple glistening yellow white dots

Fibrillar degeneration of vitreous

Rare

Association: Cataract formation , Corneal guttae

PERIPHERAL MICROCYSTOID DEGENERATION

Most commonly seen in temporal quadrant

Tiny cystic vesicles with indistinct boundaries on a grayish-white background which make the retina appear thickened & less transparent

Lesion may coalesce with each other & leads to senile retinoschisis.

RETICULAR (HONEYCOMB)

DEGENERATION

Most prominent in nasal quadrants , may extend posterior to the equator

Characterised by a fine network of perivascular pigmentation which Age related change.

Nil

Caused by RPE degeneration

Dr Subham Sinha Roy
Fellow, Department of Vitreoretina, Sankara Nethralaya
Dr. Subham Sinha Roy , completed his MBBS from Agartala Govt. Medical College , Agartala and did his post graduation from Sarojini Naidu Medical College , Agra. He has completed his Medical retina fellowship from Sankara Nethralaya, Kolkata and presently undergoing long term Vitreo – retina Fellowship at Shri Bhagwan Mahavir Vitreoretinal Services, Sankara Nethralaya , Chennai
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