An analysis of the effect of intravitreal blood on visual acuity

We investigated the effect of diffuse hemorrhage on Snellen visual acuity in a model of vitreous hemorrhage in phakic and aphakic eyes. Two cylindrical test chambers with optical paths of 17 mm and 23 mm were constructed to simulate the effect of vitreous hemorrhage in phakic and aphakic eyes. The visual acuity was measured in two subjects in a double-masked fashion for 17 dilutions of whole blood between 1/100 and 1/12,800. The visual acuity decreased approximately linearly between the 1/800 and 1/4,800 dilutions of blood. The visual acuity was 20/20 in all dilutions of blood higher than 1/4,800. The visual acuity was reduced to hand motions or worse with 12.5 microliter of blood in the 5-ml test chamber under all test conditions. The visual acuity was 20/20 in all tests with 1.04 microliter of blood in the test chamber. The visual acuity decreased from 20/20 to hand motions with only a twelve-fold change in concentration of blood in the test chamber.