Pressure-Induced Ischemia in the Cat

Kim, Si Yeol; Jung, Yoong Jae; Shin, Jae Pil

Abstract

The effects of pressure induced ischemia on the retina were studied by means of Electroretinogram(ERG) and Electron microscopy. Acute ischemias were induced in the cat's eyes by raising the intraocular pressure over the systolic pressure for 90 minutes in group one and 3 hours in group two. ERGs and OPs(Oscillatory potentials) were recorded 1 hour. 1 day, 3 days, 7 days and 14 days after prsssure-induced ischemia, respectively. The eyes were enucleated 1 hour, 1 day, 3 days, 7 days and 14 days after ischemia for evaulation of structural damage of the retina. The amplitudes of a-, b-waves and the summed amplitudes of OPs(SOP) were decreased to 57.4%, 51.9% and 45.2% of control values at one day after ischemia and then recovered to 80%, 68.8% and 59% at 14 days after ischemia in group one. In group two, the amplitudes of a-, b-waves and the summed amplitudes of OPs appeared to flat at 1 hours after ischemia and then recovered to 50%, 50% and 30.7% of control values at 14 days after ischemia. In group one, electron microscopic study revealed generalized retinal damages including retinal edema and the pyknosis of the nucleus. And these changes seemed to be recovered gradually until two weeks after damages. In group two, the retina received more severe ischemic damages than group one, such as destruction of photoreceptors, necrosis of photoreceptor, bipolar cells and ganglion cells on one day after ischemia. After 2 weeks, the loss of photoreceptors and the pigment epithelial migration into the inner retinal layer were noted. In conclusion, the ERG study revealed that the OPs was the most vulnerable components to the ischemia and the histopathological study showed that the photore ceptors received more severe damage from the retinal ischemia than the other components.