A stereological analysis of venous nicking observed at retinal arteriovenous crossings

The accepted hypotheses for the explanation of retinal venous nicking are critically reviewed and an alternative hypothesis based on a stereological analysis is presented. The ophthalmoscopic appearance of retinal venous nicking is best explained by partial collapse of the vein with the major axis of the venous cross section at right angles to the internal limiting a membrane of the venous blood flow nor of the likelihood of tributary vein occlusion. A partially collapsed vein may be very sensitive to small changes in intraocular pressure. Patients with impending tributary vein occlusion may benefit from reducing intraocular pressure.