Hematological Disease — Retinopathy

Overview

The retina is the only place in the body where blood vessels can be examined directly and non-invasively, which makes it an unusually visible window into systemic hematologic disease. Retinal capillaries are extremely narrow and metabolically demanding, so anything that changes the rheology of blood — abnormal red cell shape, excess white cells, elevated viscosity, or a failure of clot formation — tends to show up there first and clearly, often before a patient has any visual symptoms at all.

Two broad mechanisms account for nearly every finding covered here. The first is ischemia: abnormal cells (sickled red cells, leukemic blasts) or sluggish flow (hyperviscosity) physically occlude small retinal vessels, starving downstream retina of oxygen and eventually triggering neovascularization. The second is hemorrhage: fragile, anemic, or thrombocytopenic capillaries bleed spontaneously into or under the retina. Recognizing which mechanism is at play — and which systemic disease is driving it — is often possible from the fundus appearance alone, which is exactly why these findings are such efficient exam material.

Clinical Features

Sickle Cell Retinopathy

In sickle cell disease, sickled erythrocytes chronically occlude peripheral retinal arterioles, producing a spectrum of findings that progress from simple vaso-occlusion to frank neovascularization. Notably, proliferative retinopathy is more common and more severe in HbSC genotype than in HbSS, likely because the somewhat higher hematocrit in HbSC disease increases blood viscosity relative to the degree of vaso-occlusion.

Early in the disease, rupture of peripheral retinal arterioles produces a salmon patch hemorrhage — a superficial, orange-red preretinal or intraretinal hemorrhage. These typically resolve on their own, sometimes leaving behind a black sunburst sign: a peripheral chorioretinal scar with dark, spiculated pigment clumping, caused by RPE hyperplasia and migration over the site of a resorbed hemorrhage. Both are nonproliferative findings and don't themselves threaten vision.

The disease is formally staged by the Goldberg classification, which tracks the progression from peripheral vaso-occlusion to sight-threatening neovascular complications:

• Stage I — Peripheral arteriolar occlusion.
• Stage II — Peripheral arteriovenous anastomoses, as blood reroutes around occluded segments.
• Stage III — Sea fan neovascularization: fan-shaped neovascular fronds that grow at the junction between perfused and nonperfused peripheral retina, named for their resemblance to the marine organism.
• Stage IV — Vitreous hemorrhage, from bleeding of the fragile new vessels.
• Stage V — Retinal detachment, typically tractional, from fibrovascular contraction at the neovascular fronds.

Sickle cell disease also carries an increased incidence of angioid streaks — irregular, radiating breaks in Bruch membrane — thought to relate to iron deposition and calcification that weakens the membrane over time.

Leukemic Retinopathy & Roth Spots

Leukemia affects the retina through a combination of direct leukemic cell infiltration and the anemia and thrombocytopenia that accompany bone marrow replacement, producing capillary fragility. The most common presentation is flame-shaped or dot-blot retinal hemorrhages, often with a pale or white center — the classic Roth spot, formed by a central aggregate of white blood cells or fibrin-platelet debris surrounded by hemorrhage.

Roth spots are strongly associated with leukemia but are not specific to it — they also occur in infective endocarditis (from septic emboli or immune complex deposition), severe anemia, and diabetic retinopathy. In a febrile patient with a new heart murmur, a Roth spot should immediately prompt urgent evaluation for infective endocarditis rather than being assumed to be hematologic.

A separate and more dangerous presentation is direct leukemic infiltration of the optic nerve, which causes rapid, painless, often bilateral vision loss. Because permanent optic atrophy can develop quickly, this is an ophthalmic emergency requiring urgent radiotherapy, typically combined with systemic or intrathecal chemotherapy, to prevent irreversible visual loss.

Hyperviscosity Syndrome

When circulating protein or cell content raises blood viscosity enough to slow flow through the retinal microvasculature, the classic finding is sausage-link venous dilation — segmental, beaded dilation of the retinal veins — accompanied by scattered retinal hemorrhages and disc edema. The mechanism is straightforward stasis: viscous blood moves sluggishly through the veins, and the vessel wall responds with irregular segmental dilation rather than a smooth, uniform caliber.

The most classic cause is Waldenström macroglobulinemia, a lymphoplasmacytic lymphoma that secretes large quantities of IgM paraprotein. Because IgM is a large pentameric molecule, even modestly elevated levels disproportionately raise serum viscosity compared to smaller immunoglobulins.

Other Hematologic Findings

Several other blood disorders produce their own distinct retinal signatures:

• Thrombotic thrombocytopenic purpura (TTP) can cause a Purtscher-like retinopathy — cotton-wool spots and retinal hemorrhages clustered around the disc and posterior pole, from microvascular occlusion by platelet-fibrin microthrombi.
• Severe thrombocytopenia, regardless of cause, most commonly manifests ophthalmically as subconjunctival and retinal hemorrhages — a straightforward consequence of impaired hemostasis, not an ischemic or exudative process.
• Polycythemia vera produces a dusky, plethoric fundus with dilated, tortuous retinal veins, driven by increased red cell mass and blood viscosity; it can progress to frank retinal venous occlusion.
• Multiple myeloma can rarely present with an orbital plasmacytoma — a mass of malignant plasma cells causing proptosis, globe displacement, and diplopia.
• Iron deficiency anemia produces a classic bedside sign on eyelid eversion: marked pallor of the palpebral conjunctiva, since reduced hemoglobin concentration dulls the normally pink, well-vascularized appearance of this tissue. Iron deficiency is also thought to thin scleral collagen, producing a bluish "blue sclera" appearance from visible underlying choroidal pigment showing through.

Diagnosis / Workup

Most of these findings are identified on dilated fundus exam, with the specific pattern (sea fans, Roth spots, sausage-link veins, disc-centered cotton-wool spots) directing which hematologic workup to pursue — a CBC with differential and hemoglobin electrophoresis for suspected sickle cell disease, blood cultures and echocardiography when a Roth spot raises concern for endocarditis, and serum protein electrophoresis/viscosity measurement for suspected hyperviscosity syndrome. Fluorescein angiography is useful for staging sickle cell retinopathy, since it delineates the border between perfused and nonperfused peripheral retina where sea fans arise.

Management

Proliferative sickle cell retinopathy (Goldberg stage III and beyond) is treated with sectoral scatter laser photocoagulation, applied only to the peripheral ischemic retina feeding the sea fans. This is a deliberate contrast with diabetic retinopathy: proliferative diabetic retinopathy is treated with full panretinal photocoagulation because the ischemia is diffuse and circumferential, whereas sickle cell neovascularization tends to arise from localized peripheral nonperfusion, so treating the whole retina would be both unnecessary and needlessly destructive of functioning tissue.

Hyperviscosity syndrome from Waldenström macroglobulinemia is a hematologic emergency treated with plasmapheresis — plasma exchange rapidly removes circulating IgM, lowering serum viscosity and reversing the venous congestion and hemorrhages before permanent damage occurs.

Leukemic optic nerve infiltration is managed with urgent radiotherapy alongside systemic/intrathecal chemotherapy, as above, given how quickly vision loss can become permanent.

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