Effects of local hypothermia on ischemic eyes in vitrectomy

The effects of local hypothermia on postoperative inflammation, electroretinogram (ERG) and histological changes of the retina were evaluated in experimental vitrectomy in pressure-induced ischemic rabbit eyes. The solutions used for intraocular perfusion were maintained at 8 degrees C, 22 degrees C or 38 degrees C. Following closed vitrectomy, the vitreous cavities of the rabbit eyes were irrigated for 30 minutes with the perfusion pressure set at 70 mmHg. The blood flow in the posterior area of the eye was reduced to about one-sixth of the preoperative level during ischemia. Aqueous protein concentrations showed no significant diversities among the different temperature groups on postoperative days 1 and 7. Recovery of ERG was investigated after a given time of ischemia. There were no significant differences in the recovery of either a-wave or b-wave amplitudes among the different temperature groups; although the average b-wave amplitude in the 38 degrees C group alone failed to return to the preoperative level on the 7th postoperative day. Light microscopy showed an irregular distribution of retinal damage in all groups. The damaged regions showed significantly greater histologic impairment in the 38 degrees C group than in either the 8 degrees C or 22 degrees C group. The results of our experiments suggest that local hypothermia during vitrectomy in ischemic eyes decreases retinal damage and, therefore, it seems inadvisable to use intraocular solutions warmed to body temperature.