Which physical findings are characteristic of proliferative sickle retinopathy?

Updated: Sep 03, 2019
  • Author: Brian A Phillpotts, MD; Chief Editor: Hampton Roy, Sr, MD  more...
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Answer

This retinopathy is characterized by neovascularization that results from repeated episodes of ischemia secondary to repetitive or successive peripheral arterial occlusions. Although neovascularization may be seen in the optic disc and the macula, proliferative sickle retinopathy is primarily a peripheral retinal disease. Goldberg proposed the universally accepted classification for PSR in 1971, which is divided into 5 discrete stages.

Stage I - Peripheral arteriolar occlusion

Seen by ophthalmoscopy, areas of retinal ischemia secondary to nonperfusion become an abnormal grayish brown color.

The exact pathogenesis is not known, but it is theorized and accepted that sickled erythrocytes cause occlusion secondary to increased viscosity, followed by stasis and subsequent thrombosis.

Why the peripheral retina more commonly is affected than the posterior pole remains unclear. Vessel luminal diameter, critical closing pressure, and oxygen tension in the peripheral retinal appear to play important roles in development.

Fluorescein angiography helps delineate areas of avascular and abnormal capillary bed from the normally perfused retina.

Stage II - Arteriolar-venular anastomoses

These anastomoses are characterized by the shunting of blood from the occluded arterioles to the nearest venules.

Following peripheral arteriolar occlusions, vascular remodeling ensues at the junction between the perfused posterior and nonperfused peripheral neural retina.

Unoccluded arterioles develop collateral circulation through the preexisting capillaries, resulting in arteriolar-venular anastomoses.

This is not neovascularization.

Clinically, these anastomoses may be difficult to view via ophthalmoscopy. Fluorescein angiography can demonstrate arteriovenous anastomoses that do not leak dye.

Stage III - Neovascular proliferation

Repeated ischemic events lead to neovascular proliferation.

In the early stage of development, these neovascular fronds are small and lie flat on the retinal surface. With time, these abnormal vascular fronds grow in size and take on the characteristic appearance that resembles the marine invertebrate Gorgonia flabellum, hence the name "sea fan neovascularization." Sea fans are not pathognomonic.

Fluorescein angiography can help identify very small sea fan lesions. Unlike arteriolar-venular anastomoses, which do not leak, sea fan lesions leak profusely.

Patients with sea fan neovascularizations are at increased risk for developing vitreous hemorrhage and retinal detachment.

Epidemiologically, patients with sickle cell C disease are more likely to present with neovascularization than patients with sickle cell-thalassemia disease.

Sea fans often autoinfarct or spontaneously regress (20-60%).

Supposedly, these neovascular fronds are strangulated by fibroglial tissue. The acute occlusion of the sea fan feeding arteriole may result in autoinfarction.

Stage IV - Vitreous hemorrhage

Vitreous hemorrhage can result from PSR or trauma; it may be spontaneous secondary to vitreous collapse and/or traction of the adherent neovascular tissue.

When the vitreous collapses, either from liquefaction that is associated with aging or degenerative changes secondary to chronic leakage from sea fans, traction is exerted on the neovascular tissue.

The force exerted on the sea fans by the vitreous can tear the neovascularized and retinal vessels, leading to vitreous hemorrhage.

The degree of hemorrhage varies (ie, small or large, bleeding can occur at irregular intervals for several years). Vitreous hemorrhage may be small and localized or large enough to cloud the entire center of the vitreous cavity, giving rise to visual symptoms.

Patients with sickle cell C disease are most likely to develop neovascular proliferation, and they are more likely to present with vitreous hemorrhage.

Stage V - Retinal detachment

Retinal detachments may be rhegmatogenous and/or tractional. Traction from bands and membranes on the neovascular tufts can lead to sufficient retinal traction with or without retinal tears, both of which may lead to retinal detachment.

Another proposed theory for retinal detachment in hemoglobinopathies is retinal atrophy. Retinal ischemia can result in retinal thinning, retinal hole formation, and, subsequently, retinal detachment.

Clinically, the retinal tears that lead to retinal detachment are small to moderate in size and ovoid or horseshoe in shape.

The pathogenesis of hemoglobinopathy retinal tears and detachment is similar to proliferative diabetic retinopathy and other proliferative retinopathies.

Patients with sickle cell C disease are more likely to develop retinal detachment than patients with other forms of hemoglobinopathies.


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