Permeability of abnormal blood-retinal barriers in rat phototoxic retinopathy: a clinicopathologic correlation study using fluorescent markers.

Phototoxic retinopathic rats were studied by vitreous fluorophotometry (VF) and histofluorescence microscopy using NaFl and FITC-Dextran molecules of selected molecular sizes as blood-retinal barrier permeability determinants. Retinopathic rats had significantly higher VF values than normal rats at a 35 mg/kg NaFl dosage; detectable levels were not obtained with 3.5 mg/kg NaFL nor with FITC-Dextrans. However, as demonstrated by histofluorescence microscopy, NaFl and FITC-Dex 3 molecules readily passed the abnormal BRB tissues to enter neural retina and vitreous space whereas FITC-Dex 20, 40, 70 and 150 molecules did not, except under certain circumstances. These studies indicate a barrier defect of both the retinal vessels and RPE is responsible for the in vivo demonstrated permeability abnormality.