Snellen visual acuity and spatial contrast sensitivity measurements were used to monitor changes in foveal vision in two patients undergoing argon laser panretinal photocoagulation (PRP) in both eyes for proliferative diabetic retinopathy. Foveal edema developed in one of the four eyes. The remaining three eyes showed no signs of foveal edema, but developed temporary losses in high spatial frequency contrast sensitivity during the closely spaced PRP treatments. Since Snellen visual acuity remained stable at the prelaser level, these results indicate the need for more sensitive measures of visual resolution to monitor foveal integrity in patients undergoing PRP.