Laser photocoagulation in a grid pattern is effective in many eyes in resolving diffuse diabetic macular edema and stabilizing vision. We retrospectively studied 203 eyes of 203 patients, all of whom had diabetic macular edema treated with grid laser photocoagulation. During the follow-up period, 11 of these 203 eyes developed enlargement of the laser scars that progressed into the central fovea. Each of the 11 eyes experienced loss of vision, and in five, the visual loss was significant. Five of these eyes also developed a retinal pigment hyperplastic scar. After the laser treatment, but before the scars enlarged, the visual acuity of these eyes was unchanged from that before treatment. But after the atrophic scars enlarged into the central fovea, visual acuity in one eye decreased from 20/40 to 20/100, and the other 10 eyes had visual acuities of 20/200 or worse.