Panretinal photocoagulation as well as vitrectomy are the main treatment modalities for diabetic and other proliferative retinopathies. We show that both treatments introduce a new source of oxygen to the inner retina and propose that their efficacy in controlling the retinopathy results from their effect on the oxygenation of the inner retina. Panretinal photocoagulation reduces the oxygen consumption of the outer retina and allows more oxygen to diffuse to the inner retina from the choroid. Vitrectomy/lensectomy on the other hand allows aqueous humor to flow back to the retina and give oxygen to the inner retina which normally has a lower PO2 than aqueous humor. This causes the PO2 in aqueous humor to fall.