Short–term changes in the multifocal ERG measured in macaque eyes with laser–induced ocular hypertension

Abstract

Abstract: : Purpose: To study the early changes in the multifocal (mf) ERG measured in macaques after laser–induced ocular hypertension. Methods: mfERGs were measured in six anaesthetized macaques repeatedly before and after laser induced ocular hypertension in one eye. Before laser surgery, two baseline measurements were performed in the two eyes with about three weeks’ intervals. Up to several months after laser surgery, the two eyes were measured in about two weeks’ intervals. Results: Before laser surgery, the 1^st order kernels of mfERGs recorded in the same eye but with three weeks' interval were very similar. Furthermore, the mfERGs recorded from the left and the right eyes strongly resembled each other. Comparison of mfERGs performed in the eyes of different animals showed much larger differences although all mfERGs shared several features. In two animals, the mfERGs in the eyes that underwent laser surgery were clearly altered already two to four weeks after laser surgery. The intraocular pressures (IOPs) in these eyes were continuously increased. In these animals, the mfERGs in the fellow eyes were not changed. The remaining four animals did show no or mild changes in the mfERGs up to two months after laser treatment. The IOPs in these animals were either normal, increased or temporarily increased. Conclusions:Laser induced changes can be observed very early after treatment. An increased IOP is probably necessary but not sufficient to induce early changes in the mfERG. Retinal development within an animal is probably an extremely stringent process leading to very similar ERG signals in the two eyes of an individual animal. However, this developmental process can differ between individuals.

Keywords: electroretinography: clinical • electroretinography: non–clinical