Non‐invasive measurement of retinal permeability in a diabetic rat model

Objective The gold standard for measuring blood‐retinal barrier permeability is the Evans blue assay. However, this technique has limitations in vivo, including non‐specific tissue binding and toxicity. This study describes a non‐toxic, high‐throughput, and cost‐effective alternative technique that minimizes animal usage. Methods Sodium fluorescein fundus angiography was performed in non‐diabetic and diabetic Brown Norway rats on days 0, 7, 14, 21, and 28. Sodium fluorescein intensity in the retinal interstitium and a main retinal vessel were measured over time. The intensity gradients were used to quantify retinal vascular permeability. Post‐study eyes were fixed, dissected, and stained (isolectin B4) to measure required parameters for permeability quantification including total vessel length per retinal volume, radius, and thickness. Results In the non‐diabetic cohort retinal permeability remained constant over the 28‐day study period. However, in the diabetic cohort there was a significant and progressive increase in retinal permeability from days 14‐28 (P