Progress in measurement of ocular blood flow and relevance to our understanding of glaucoma and age-related macular degeneration

New technologies have facilitated the study of the ocular circulation. Thes e modalities and analysis techniques facilitate very precise and comprehens ive study of retinal, choroidal, and retrobulbar circulations. These techni ques include: 1. Vessel caliber assessment; 2. Scanning laser ophthalmoscop ic fluorescein angiography and indocyanine green angiography to image and e valuate the retinal circulation and choroidal circulation respectively; 3. Laser Doppler flowmetry and confocal scanning laser Doppler flowmetry to me asure blood how in the optic nerve head and retinal capillary beds; 4. Ocul ar pulse measurement; and 5. color Doppler imaging to measure blood flow Ve locities in the central retinal artery, the ciliary arteries and the ophtha lmic artery. These technique have greatly enhanced the ability to quantify ocular perfusion defects in many disorders, including glaucoma and age-rela ted macular degeneration, two of the most prevalent causes of blindness in the industrialized world. Recently it has become clear, in animal models of glaucoma, that retinal ganglion cells die via apoptosis. The factors that initiate apoptosis in these cells remain obscure, but ischemia may play a c entral role. Patients with either primary open-angle glaucoma or normal-ten sion glaucoma experience various ocular blood flow deficits. With regard to age-related macular degeneration, the etiology remains unknown although so me the ories include primary retinal pigment epithelial senescence, genetic defects such as those found in the ABCR gene which is also defective in St argardt's disease and ocular perfusion abnormalities. As the choriocapillar is supplies the metabolic needs of the retinal pigment epithelium and the o uter retina, perfusion defect in the choriocapillaris could account for som e of the physiologic and pathologic changes in AMD. Vascular defects have b een identified in both nonexudative and exudative AMD patients using new te chnologies. This paper is a comprehensive update describing modalities avai lable for the measurement of all new ocular hood how in human and the clini cal use. (C) 1999 Elsevier Science Ltd. All rights reserved.