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Fluorophotometry was used to evaluate alterations in the blood-ocular barrier to fluorescein in rats with experimental hypertension. One hour after intravenous injection of fluorescein, 16.6 mg/kg, concentrations in the anterior chamber were increased from mean normotensive values of 135 micrograms/mL to 299 micrograms/mL (P = .005) in animals with severe hypertension. Fluorescein concentrations in the vitreous also were increased from 50 micrograms/mL in normotensive rats to 109 micrograms/mL (P = .005) in hypertensive animals. With increasing duration of systemic pressures above 160 mm Hg, anterior chamber fluorescein concentrations rose from base-line of 135 micrograms/mL to 210 micrograms/mL after one to four weeks of hypertension, and to 394 micrograms/mL after five to eight weeks (P = .005). Similarly, vitreous concentrations increased from baseline of 50 micrograms/mL to 76 micrgrams/mL and 136 micrograms/mL (P = .005) after the shorter and longer periods of hypertension. Control of hypertension with return of systolic pressure to below 120 mm Hg caused a reversal of the abnormal fluorescein permeability.