Forty-two eyes of 31 proliferative diabetic retinopathy patients with laser flare intensity > or = 20 photon counts/ms underwent fluorescein iris angiography to evaluate any changes in the blood-iris barrier and iris biomicroscopy to detect rubeosis iridis. Fluorescein iris angiography revealed abnormal dye leakage in all eyes. Laser flare intensity significantly correlated with the degree of dye leakage. Eyes with dye leakage from only the pupillary border had no rubeosis. In 11 out of 18 (61%) eyes with moderate dye leakage, proliferative diabetic iridopathy with early rubeosis was present in 8 and advanced iridopathy in 3 eyes. In all eyes with excessive leakage, rubeosis iridis was detected under slitlamp examination. High laser flare intensity has a close relationship with advanced blood-ocular barrier disruption. High flare intensity may be a helpful indicator in detecting incipient rubeosis or advanced diabetic iridopathy.