The effect of laser on the pattern electroretinogram: A primate model

The pattern electroretinogram (PERG) is a small (<6 μV) electrical response thought to originate in the inner retinal layers, and it is ganglion cell-dependent. To establish the effect of laser photocoagulation on the PERG we treated both eyes in three rhesus monkey and measured PERGs at 5 times over a 60 day period. Following two or three baseline studies, the area within the arcades was photocoagulated in each monkey's right eye (approx. 10-15% of total retina, resulting in 5% photoreceptor death), and the peripheral retina was photocoagulated in each left eye (50-60% of total retina, resulting in 35% photoreceptor death). There was a statistically significant, but temporary, depression of the PERG amplitude at 1 week post-treatment in both eyes even though only the central 30 x 36° of retina was directly stimulated by counterphasing checkerboards. The eyes with central photocoagulation and the eyes with peripheral photocoagulation were similar to baseline PERG values at all other time points. The PERG implicit time was unchanged from baseline at all post-laser timepoints regardless of the area of retinal photocoagulation. These findings suggest that the PERG may have clinical application in the assessment of the inner retinal layers in human diabetics who have received laser photocoagulation.