Measuring and interpreting ocular blood flow and metabolism in glaucoma

There is a growing body of evidence suggesting that vascular dysfunction is related to several prominent ophthalmic diseases, including glaucoma. The vast majority of studies providing data on ocular circulation and disease pathophysiology use a relatively small number of complicated ocular blood flow imaging techniques. Although these imaging technologies are not commonly used in clinical settings, understanding the medical literature characterizing ocular blood flow requires familiarity with their methodology and function. This review highlights the imaging technologies most commonly used to investigate ocular blood flow, including color Doppler imaging, confocal scanning laser ophthalmoscopic angiography with fluorescein and indocyanine green dye, Canon laser blood flowmetry, scanning laser Doppler flowmetry, and retinal photographic oximetry. Each imaging technique's ability to define vascular function and reveal pathology is discussed as are limitations inherent to each technology. The ultimate goal of this review is to provide the physician with a clinically relevant foundation for differentiating the various ocular blood flow outcome measures often presented in the literature and determine how they are related to ocular health and disease.