Effects of panretinal photocoagulation on photopic ERG in normal rabbit eyes

The effects of panretinal photocoagulation (PRP) on photopic ERG were studied in normal pigmented rabbit eyes. Photopic ERGs were recorded before PRP and one day, one week and 4 weeks after PRP. Markedly reduced amplitude and delayed implicit time were observed one day after PRP. Four weeks after PRP, amplitude showed subtotal recovery while implicit time, showing tendency of reduction, was still significantly delayed. The delay in implicit time and the reduction in amplitude after PRP was probably due to serous retinal detachment and/or retinal edema caused by breakdown of the blood-retinal barrier. However, the findings at 4 weeks after PRP might be explained by the reduced number of photoreceptor cells; the mild decrease in the amplitude of photopic ERG might be caused by the reduced number of cones, while significantly delayed implicit time of the photopic ERG might be caused by reduced number of rods.