Nonarteritic Disease
Nonarteritic problems with flow could occur due to embolic or systemic disease or as part of the manifestation of severe hypertension. Emboli from the heart, corticosteroids or calcium hydroxyapatite injection, and intravascular coagulation all have the potential to occlude choroidal vessels. Vascular occlusion could also occur in patients with lupus anticoagulants. Thrombotic thrombocytopenic purpura causes a classic pentad of findings: (1) microangiopathic hemolytic anemia, (2) thrombocytopenia, (3) fever, (4) neurologic dysfunction, and (5) renal dysfunction. Patients with this condition may have multifocal yellow placoid areas and associated serous detachment of the retina. Similar fundus findings may occur in patients with disseminated intravascular coagulation, in which consumption of coagulation proteins, involvement of cellular elements, and release of fibrin degradation products lead to hemorrhage from multiple sites and ischemia from microthrombi.
Similar fundus findings occur in patients with acute hypertension, such as malignant hypertension or eclampsia (Fig 9-10). In addition to retinal and optic nerve head abnormalities, these disorders also commonly lead to serous detachment of the retina associated with areas of yellow placoid discoloration of the RPE (see Fig 9-10). The perfusion abnormalities may range from focal infarction of the choriocapillaris to fibrinoid necrosis of larger arterioles. Resolution of smaller infarcts, which initially appear tan in color, produces small patches of atrophy and pigmentary hyperplasia called Elschnig spots. Infarction of an arteriole can lead to Siegrist streaks, while sector-shaped abnormalities are called Amalric triangles.
Older patients may have areas of slow blood flow in the choroid, causing choroidal filling defects. The flow problems may result from low inflow pressure. Histologic sections of eyes of older patients may reveal intimal hyperplasia and medial hypertrophy with a decrease in the lumen size. This change may also adversely affect blood flow. Decreased flow in the segmentally arranged choroid can cause areas of particularly decreased perfusion between areas of low perfusion; these are called watershed defects.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.