A review of ocular blood flow measurement techniques

Several major eye diseases may be characterized by deficits in ocular blood flow. Maintaining adequate nutrient delivery to the choroid, retina, and optic nerve head may prevent cellular damage and loss, complementing efforts to provide neuroprotection. The ability to quantify deficits in ocular blood flow has increased in recent years with the introduction of several new techniques. 1) Scanning laser ophthalmoscopic fluorescein angiography allows the measurement of bulk retinal flow and macular capillary transit rates. 2) Scanning laser ophthalmoscopic indocyanine green angiography measures choroidal perfusion in selected areas near the optic nerve head and macula. 3) Confocal scanning laser Doppler flowmetry permits quantitation of retinal capillary perfusion. 4) Color Doppler ultrasound imaging measures flow velocities in the ophthalmic, central retinal, and short posterior ciliary arteries. While these techniques represent a major advance, significant issues regarding blood flow and ocular disease remain. First, the hemodynamic characteristics of the disease state need further definition. Second, the blood flow effects of current and future treatments must be established. Third, improvements in ocular blood flow techniques are required, both to increase anatomic precision and to allow non-invasive measurements during times of potential ischemic risk such as sleep. These developments could enhance prevention, diagnosis, and treatment of several major eye diseases.