The optical, electronic sensoring and data acquisition systems were assembled and the software developed for a vitreous fluorophoto-meter which was then calibrated and used to quantify the integrity of the blood-retinal barrier in a pilot study of diabetic retinopathy and multiple sclerosis compared to normal controls. Breakdown of the blood-retinal barrier was quantified by measuring fluorescence in the vitreous at standard time intervals over one hour following intravenous injection of sodium

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... fluorescein. The plasma dye concentration was measured throughout the procedure. Leakage was expressed as a penetration ratio of the average concentration at 3mm from the retina to the total plasma dye concentration. The results from diabetic subjects showing well defined stages of retinopathy severity demonstrated the proper functioning of the instrument by showing values in approximate agreement with retinopathy severity, thus confirming the findings of previous observers. Of 16 multiple sclerosis subjects, results showed no significant difference between activity categories or level of current activity. Abnormally high penetration ratio was associated with active periphlebitis. A new finding was the presence of abnormally high leakage in 2 subjects showing no ocular signs of disease. Subjects without or with inactive periphlebitis showed breakdown of the blood-retinal barrier comparable in severity to diabetic subjects showing no or mild retinopathy. The vitreous diffusion constant of the dye for normal controls and multiple sclerosis subjects was not significantly different from that in water.