Fluorometric evaluation of panretinal photocoagulation in diabetic subjects

The effect of panretinal photocoagulation on the blood-retinal barrier was examined by long-term kinetic vitreous fluorophotometry in eight insulin treated diabetic subjects, before and one month after unilateral panretinal photocoagulation. The fluorophotometric investigations revealed an increased permeability-index following this treatment. A further analysis based upon a two-compartment fluorescein kinetic model revealed a decreased penetration rate constant together with increased zero-time concentration coefficients for fluorescein following panretinal photocoagulation. No alterations were observed in kinetic parameters in the group of untreated eyes. This points towards a delayed but increased fluorescein penetration to the vitreous following panretinal photocoagulation, probably indicating an increased net flux of fluorescein across the entire retina. In patients with unilateral proliferative retinopathy the permeability-index obtained from eyes with classified proliferative retinopathy was 18.1%, whereas the permeability-index from eyes without proliferative retinopathy was 15.4%. This relatively small difference seems to indicate that the main part of vitreous fluorescence comes from an increased penetration across the entire retina, whereas a direct leakage from the proliferations themselves is less in magnitude. This increased retinal penetration might possibly be caused by affected transport processes for fluorescein within the retina.