Purpose: The study was designed to quantify retinal vein width changes at the arterio-venous crossing and to evaluate the effects of hypertension on vein widths at "vein posterior to the artery" (VPA) and "vein anterior to the artery" (VAA) crossings.
Methods: The width of the retinal veins was measured at points before and after the arterio-venous crossings by a computerized image analysis system in ten normal subjects and 35 hypertensive patients. Retinal vein width changes at fixed intervals from the arterio-venous crossing points, both VAA and VPA, were measured as a function of the stage of the hypertensive retinopathy in the subjects.
Results: Mean retinal vein width showed significant (p < 0.05) narrowing at VPA crossings at stages 2, 3 and 4 of hypertensive retinopathy. For the VAA crossings, there was no significant decrease in the width of the vein at any stage. There was no significant narrowing of the vein at VPA crossings in normal subjects or in stage 0 and stage 1 hypertensive retinopathy patients.
Conclusions: The decrease in the width of the retinal vein in stages 2, 3 and 4 hypertensive retinopathy patients at VPA crossings can cause turbulence in blood flow, leading to intimal damage and occlusion. The absence of narrowing may explain the low incidence of branch retinal vein occlusions at VAA crossings.