The clinical measurement of endothelial permeability

The endothelium maintains corneal deturgescence in part by serving as a barrier to fluid movement into the cornea. This barrier function is estimated by measuring the permeability of the endothelium to small, nontoxic, fluorescent molecules such as fluorescein and carboxy-fluorescein. After topical or systemic application of the dye, its concentration in the cornea and the anterior chamber is measured noninvasively at intervals over several hours with a fluorophotometer. Endothelial permeability to the fluorescent dye is calculated from the changes in its concentration in the cornea and anterior chamber over time. The permeability of the endothelium to the small fluorescent molecules is assumed to be proportional to its permeability to water, and thus provides an estimate of the barrier function of the endothelium. This paper reviews the theory and technique of clinical fluorophotometry and discusses published data concerning the effects on endothelial permeability of aging, contact lens wear, medication, and surgery.