PIGMENTED LESIONS

Choroidal nevus

Choroidal melanoma

Clinical Features

Pigmented lesions originating in the retina are typically black with distinct borders. Pigmented lesions originating in the choroid or retinal pigment epithelium (RPE) tend to be gray with less distinct borders.

Differential Diagnosis

The most common pigmented lesion of the choroid, the choroidal nevus, has certain characteristics: it is flat, round or oval, and dark gray. A nevus may vary from a few hundred micrometers to several disc diameters in size. Older nevi often have drusen on the surface and are surrounded by a halo of atrophy. Malignant melanomas are elevated, pigmented lesions of the choroid. Experts in the field of ocular oncology consider certain clinical features highly suggestive of a melanoma, including greater tumor thickness, orange pigment of the surface of the tumor, the absence of drusen, and the presence of subretinal fluid. A rare pigmented tumor of the uveal tract is bilateral diffuse uveal melanocytic proliferation,

Congenital hypertrophy of the retinal pigment epithelium

Bear tracks

a paraneoplastic syndrome consisting of multiple flat pigmented choroidal lesions.

Pigmented lesions may arise from the RPE. Congenital hypertrophy of the RPE (CHRPE), a benign condition typically seen in the mid to far periphery, is characterized by a circular area of heavy pigmentation with a scalloped pattern of atrophy developing in its center. The presence of multiple CHRPE-like lesions has been associated with Gardner’s syndrome (familial polyposis). A black sunburst in sickle cell retinopathy represents a solitary lesion of hyperplastic RPE in an area of regressed subretinal hemorrhage. A similar lesion, RPE hyperplasia, can occur after photocoagulation in the macula. A less pigmented tumor, the combined hamartoma of the RPE and retina, typically has a fine, light gray color on its surface and may involve the optic disc.

Pigmentary lesions of the retina may be solitary or appear in clusters. Melanocytomas are solid, benign, dark black tumors often located on or near the optic disc. In grouped pigmentation of the retina, or “bear tracks pigmentation,” clusters of circular or oval lesions of varying sizes are found in the retina, in either the macula or the periphery.

Diabetic retinopathy

Retinal arterial macroaneurysm

Leukemic retinopathy

Valsalva retinopathy

Clinical Features

Preretinal hemorrhage is blood anterior to the retina but posterior to the posterior hyaloid of the vitreous. Preretinal hemorrhage typically appears bright red and obscures the retinal blood vessels beneath it. Preretinal hemorrhage often assumes a boat-shaped appearance.

Differential Diagnosis

Proliferative diabetic retinopathy and other proliferative retinopathies are common causes of preretinal hemorrhage. When a partial vitreous detachment in the macula occurs in patients with diabetes, the preretinal or “subhyaloid” hemorrhage takes on a crescent or boat-shaped appearance. In conditions in which the posterior vitreous remains firmly attached throughout the macula, such as in Valsalva retinopathy, the preretinal hemorrhage is

often more solid in appearance. In arteriolar macroaneurysms, the preretinal hemorrhage typically lies in front of intraretinal and subretinal blood.

In Terson’s syndrome, blood is trapped between the internal limiting membrane and the neurosensory retina, forming a dome-shaped area of hemorrhage. Over time, the red blood cells may settle to the inferior portion of the dome, creating a red blood cell-serous fluid level. Sub-internal limiting membrane hemorrhage may accompany subhyaloid hemorrhage in Valsalva retinopathy, airbag injuries, trauma, and shaken baby syndrome. Patients with severe leukemia may present with preretinal blood in addition to intraretinal hemorrhage.

Although the exact cause of the hemorrhage is unknown, it is postulated that a certain level of anemia and thrombocytopenia is responsible

for the hemorrhages.

Clinical Features

Retinal crystals are small, refractile deposits that are typically found in the inner retina. Because the composition of retinal crystals varies, crystals may appear white, yellow, or gold.

Differential Diagnosis

Retinal crystals can be seen in a number of conditions: degenerative disorders such as idiopathic juxtafoveal retinal telangiectasis; hereditary disorders such as cystinosis, hyperoxaluria, and Bietti’s crystalline dystrophy; and toxic retinopathies from such agents as tamoxifen, canthaxanthin, and talc.

In idiopathic juxtafoveolar retinal telangiectasis (IJRT), crystals may be deposited in the inner retina, and are clustered near but not directly under the fovea. In nephropathic cystinosis, an autosomal recessive storage disorder of excess cystine, yellow crystals are deposited in the choroid and retinal pigment epithelium (RPE).

In patients with primary and secondary hyperoxaluria,

calcium oxalate crystals are found in the retina and RPE and may form a striking periarterial pattern. The hallmark of Bietti’s crystalline tapetoretinal dystrophy is hundreds of retinal crystals scattered throughout the posterior pole.

Breast cancer patients who are treated with high doses of tamoxifen, a nonsteroidal antiestrogen, may have white crystals deposited in the superficial retina. Most commonly found temporal to the fovea, these refractile deposits are thought to represent axonal degeneration. Multiple bright, golden crystals distributed in an oval ring around the fovea are characteristic of canthaxanthin retinopathy. In addition, shiny white deposits within retinal arterioles may be seen in talc retinopathy (talc emboli) and atherosclerotic heart disease (Hollenhorst plaques).

The differential diagnosis of retinal crystals also includes Sjögren-Larsson syndrome, gyrate atrophy, and an idiopathic finding. Refractile deposits can be seen in conditions in which significant retinal atrophy is present, such as chronic retinal detachment, inactive cytomegalovirus infection, or calcified drusen.

Clinical Features

Neovascularization of the retina begins in the plane between the internal limiting membrane of the retina and the posterior hyaloid of the vitreous. The most common locations for retinal neovascularization are (1) along the vascular arcades and the optic disc (the areas of greatest adherence between the vitreous and the retina) and (2) at the border of perfused and nonperfused retina. The new vessels may form a wheel or frond but may also grow linearly along the retinal surface without forming a network. A hallmark of retinal neovascularization is that the abnormal new vessels can cross both retinal arterioles and veins.

Differential Diagnosis

Retinal neovascularization may be observed in a variety of retinal vascular diseases, inflammatory diseases, and hereditary disorders.

Proliferative diabetic retinopathy is the most common cause of retinal neovascularization. In proliferative diabetic retinopathy, neovascularization of the retina is flat and is usually observed overlying retinal veins. With vitreous contraction, the fronds may become elevated.

Radiation retinopathy can produce retinal neovascularization that is indistinguishable from diabetic new vessels. Vascular occlusive conditions, such as ischemic vein or artery occlusions, may produce retinal neovascularization due to widespread retinal ischemia. The “sea fan” pattern of sickle cell retinopathy forms in the midperipheral retina at the junction of ischemic and nonischemic retina. In retinopathy of prematurity, retinal new vessels form behind the leading edge of the developing retina and may become an elevated ridge of neovascularization. Retinal embolization and leukemia have been associated with neovascularization.

Eales’ disease is a chronic inflammatory condition in which anterior or peripheral new vessels may be accompanied by chronic phlebitis and peripheral ischemia. In some conditions, such as sarcoidosis and pars planitis, neovascularization develops as a result of inflammation rather than ischemia.

Retinal neovascularization may be observed in Norrie’s disease, incontinentia pigmenti, and familial exudative vitreoretinopathy.

Other conditions simulating retinal neovascularization include shunt vessels on the disc or retina, intraretinal microvascular abnormalities, and retinal angiomas.