The use of vitreous fluorophotometry to distinguish between diabetics with and without observable retinopathy: Effect of vitreous abnormalities on the measurement

Ten age-matched normals, diabetics with retinopathy, and diabetics without observable retinopathy were evaluated by vitreous fluorophotometry (VFL) using a 0.15 mm and a 0.45 fiberoptic probe in a photomultiplier system as well as commercially available photodiode instrument to determine whether differences in intraocular sodium fluorescein levels could be detected among the three groups. Each subject was injected in the antecubital vein with 7 mg/kg of sodium fluorescein (25% solution) and measurements were taken 1 hr postinjection at 4.5 mm and 7.5 mm from the retina. The influence of choroidal fluorescein and ocular pigmentation are reduced at these locations. We found that a breakdown in the blood-ocular barrier may not be present early in the course of diabetes. Furthermore, no significant difference was found between normals and diabetics without retinopathy. Although the mean value for vitreous fluorescein was significantly higher in diabetics with retinopathy compared to normals, several of the diabetics with retinopathy had values in the normal range. These results differ from those previously reported in the literature. However, our studies took into consideration several factors not considered by other investigators, such as ocular pigmentation, choroidal fluorescence, slit width, and vitreous changes, that may have significant effects on the fluorophotometry values.