Choriocapillaris Blood Flow Abnormalities
Choroidal blood flow defects affect lobule-sized areas of the choroid or areas supplied by arterioles and therefore affect one to several choroidal lobules. Many ocular diseases (eg, acute posterior multifocal placoid pigment epitheliopathy) characteristically produce lesions that are the putative size of a choroidal lobule. The advent of OCT angiography has uncovered another problem in choroidal circulation. The choriocapillaris develops multiple areas of signal voids, consistent with decreased perfusion. These areas increase in size and number with age; they are also larger and more numerous in patients with hypertension, pseudodrusen, or, interestingly, late age-related macular degeneration in the fellow eye. In addition, these defects exhibit power law probability distributions, which may be useful in gauging ocular and systemic health. These characteristic OCT angiographic findings are consistent with histologic studies showing an increasing number of ghost vessels in the choriocapillaris (a sign of vessel death), basal linear deposits, and subretinal drusenoid deposits with increasing age. Hayreh characterized the segmental nature of blood flow in the choroid from larger to smaller vessels and finally to the choriocapillaris lobule. The data from OCT angiography descends another unit of scale to show potential defects in capillary flow within parts of a choroidal lobule. Some diseases are known to be associated with RPE atrophy in addition to geographic atrophy; they include pseudoxanthoma elasticum and maternally inherited diabetes mellitus and deafness. Even in the absence of the development of RPE atrophy, these patients can exhibit remarkable loss of the choriocapillaris (Fig 9-11). Curiously, pseudodrusen also develop in patients with pseudoxanthoma elasticum.
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.