Classification of Peripheral Retinal Degenerations

Peripheral retinal degenerations are classified according to the following criteria:

Location- equatorial, peripheral, or combined
Pathomorphology- trophic, tractional, atrophic, or combined
Depth of retinal changes- intraretinal, retinal, vitreoretinal, or chorioretinal
Risk for retinal detachment
Prognosis – progressive or stationary

The following are the commonly used classifications of peripheral retinal degenerations based upon depth of retinal changes observed on optical coherence tomography (OCT):

Intra-retinal Degenerations: senile retinoschisis, white-without-pressure, white-with-pressure, dark-without-pressure, peripheral cystoid degeneration, snowflake degeneration, and pearl degeneration
Vitreoretinal degenerations: lattice degeneration, snail-track degeneration, retinal tufts, and peripheral retinal breaks
Chorioretinal degenerations: paving stone degeneration and peripheral retinal drusen

Utility of OCT in diagnosis

Optical coherence tomography (OCT) has been shown to greatly benefit in the diagnosis of peripheral retinal degenerations by characterizing structural elements. Such detail includes the structure, shape and depth of retinal degenerations. Peripheral OCT may further aid in differentiation between types of peripheral retinal degeneration as well associated complications including subclinical retinal detachment, retinoschisis, retinal tears and vitreoretinal adhesions or tractions. Therefore, OCT should be utilized in the initial diagnosis, treatment, and follow-up for peripheral retinal degenerations.

Intra-Retinal Degenerations

Senile Retinoschisis

Definition: senile retinoschisis (SR) is the splitting of layers of the neurosensory retina by thick fluid.
Prevalence: found in 2-7% of the general population, more common in patients 40 years and older and in hyperopic eyes
Characteristics: Lesion is a bullous elevation of peripheral retina, found in temporal segment
Findings: Mostly asymptomatic
Immobile with movement of eye and produces an absolute field defect
Complications: may involve posterior pole, may lead to retinal detachment
Primary cause of retinal detachment in 0.05-2.5% of cases
Diagnosis: OCT findings include intraretinal hyporeflective cavities with destruction and thickening of the RPE
Treatment: should be treated when patients are symptomatic, or there is progressive retinal detachment threatening the macula

White-Without-Pressure

Definition: Distinctive white appearance of the peripheral retina without indentation and without mechanical stimulus
Prevalence: found in up to 30% of normal eyes, often bilateral, more frequently diagnosed in younger patients, may be associated with longer axial length
Characteristics: Whiter than the retina in white with pressure and the choroidal markings are almost obscured, found in post-equitorial region at the base of the vitreous and ora serrata, whiteness further accentuated with scleral depression, margins are sharply demarcated from normal retina
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.
Diagnosis: OCT shows white areas correspond to hyperreflective outer retinal layers and ellipsoid zone, no vitreous traction
Treatment: low risk for association with retinal detachment, so patients are examined every 1-2 years

White-With-Pressure

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

Dark-Without-Pressure

Definition: flat, brown fundus lesion with well-defined margins in the equator of peripheral retina
Findings: can be found posterior to area of white-without-pressure and may look like retinal tear, posterior to ora serrata
Symptoms: usually none
Diagnosis: OCT findings show hyporeflectivity of the ellipsoid zone
Treatment: usually benign, follow patient for routine examinations

Peripheral Cystoid Degeneration

Definition: multiple small intraretinal microcystoid cavities, most frequently seen in temporal peripheral retina
Characteristics: yellow tiny vesicles with blurred borders on gray background
- Typical: occurs in all adults, may be complicated by fusion of cysts, development of cavities in the outer plexiform layer, and flat senile retinoschisis
- Reticular: occurs in 18% of adults, may be complicated by bullous retinoschisis with cavities found in the retinal nerve fiber layer. This form is almost always found posterior to typical PCD and tends to follow the retinal vessels

Snowflake Degeneration

Definition: small yellowish dots in the peripheral retina, appear white due to light reflection
Findings: may span wide band in more than one retinal quadrant, most often in superotemporal quadrant
- may be combined with other degenerations (e.g. retinoschisis, lattice, white-without pressure)
Prevalence: rare
Complications: retinal tears, retinal holes and retinal detachment

Pearl Degeneration

Definition: congenital retinal degeneration associated with white beads on the retina
Prevalence: found in up to 20% of patients
Characteristics: ora pearls appear like drusen, found between the retinal pigment epithelium and Bruch’s membrane or floating above RPE
Diagnosis: OCT findings show hyporeflective cavity with vitreous layers attached to top of lesion

Vitreoretinal Degenerations

Lattice Degeneration

Definition: retinal thinning with loss of neurosensory layer, vitreoretinal adhesions at margin of lesion
Prevalence: found in 6-8% of patients
Characteristics: retinal thinning with fibrosis and vitreous liquefaction over the lesion
- Typical: well-outlined thinning with white crossing lines
- Atypical: found adjacent to vessels in radial pattern
Findings: oval or linear pattern of lesions, may be one lesion or multiple, may have yellow deposits, pigment, atrophic holes, or retinal tears
Complications: risk for retinal detachment and rhegmatogenous retinal detachment due to vitreous traction
- Retinal detachment found in 14-35%
Treatment: most commonly prophylactic laser treatment recommended in patients with vitreous traction and retinal tears associated with flashes and floaters

Snail track degeneration

Definition: groups of glistening white dots (which have been compared to frost granules or salt), may be early stage of lattice degeneration
Prevalence: Found in 10% of generation population, more commonly in myopic eyes (40%)
Characteristics: retinal thinning with vitreous liquefaction above the lesion, associated vitreoretinal tractions
Findings: more often in superotemporal and superonasal quadrants
Histologically, this lesion consists of degeneration of the neural elements of retina leading to an atrophy of the tissues with lipid deposits in the internal retinal layers
Complications: may lead to retinal tears in up to 54% of patients, retinal holes
Diagnosis: OCT findings show irregular retinal surface, vitreous destruction, vitreoretinal adhesions with traction at the margins

Retinal Tufts

Definition: area of retinal degeneration caused by attachment to and pulling of the vitreous

Types include cystic, non-cystic and zonular traction tufts
Prevalence: non-cystic tufts present in up to 72% of adults, cystic present in up to 5% of adults, zonular traction tufts are present in up to 15% of adults
Complications: vitreous traction can lead to retinal tear and retinal detachment
Treatment: prophylactic laser treatment not recommended by majority of physicians, routine follow-up

Peripheral Retinal Tears

Definition: isolated tear due to defect in sensory retina from traction of vitreous after acute posterior vitreous detachment

Prevalence: 9-12% of general population

Characteristics: either retinal tear or retinal hole, retinal holes due to atrophic changes in neurosensory retina

Complications: high risk of rhegmatogenous retinal detachment, occurs in 3-18% of patients

Treatment: retinal tears with symptoms on presentation should be treated with prophylactic laser treatment, most commonly transpupillary retinopexy

Chorioretinal Degenerations

Paving Stone Degeneration

Definition: multiple rounded punched-out areas of choroidal and retinal atrophy
Characteristics: Lesions are yellow-white in color with due to sclera being partly visible through the atrophic choroid, discrete margins that may be pigmented, may become confluent
Findings: Located between ora and equator with size of one to several disc diameters
More common in infero-nasal and temporal quadrants
Large choroidal vessels seen running through the base
Prevalence: present in 4-28% of patients, bilateral, no sexual predilection, increasingly common with age
Complications: Benign lesions not associated with complications

Peripheral Retinal Drusen

Definition: extracellular protein and fat deposits between RPE and Bruch’s membrane, due to degeneration of RPE cells
Characteristics: looks like crystals
Findings: small, round-shaped, clearly outlined
Prevalence: commonly found in patients 40 years or older
Complications: benign degenerations
Treatment: prophylactic laser treatment not indicated

References

Campagnoli T.R., Smiddy W.E. (2016) Peripheral Retinal Abnormalities. In: Medina C., Townsend J., Singh A. (eds) Manual of Retinal Diseases. Springer, Cham. https://doi.org/10.1007/978-3-319-20460-4_49.
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