Objective: To investigate possible protective methods on neural damage in the rat retina during ischemia and reperfusion.

Methods: Rats were anaesthetised with ketamine and xylazine, and a single-flash electroretinogram (ERG) was obtained. Ischemia was induced by raising the ocular pressure to 130 mmHg for 60 minutes. The left eye was untreated and served as control. In one group of rats the ischemic eye was cooled, with a constant drip of cold saline. A control group received ischemia, but no other treatment. After 10 days of reperfusion ERG recordings were obtained again and eyes collected for histological assessment. All animals were treated in accordance with Icelandic law for experimental animal treatment.

Results: The ERG a-wave was measured from baseline to maximum a-wave peak and b-wave was measured from a-wave peak to maximum b-wave peak. Average decrease of the amplitudes of the a- and b-waves from initial values in the control group was 76,0% and 75,5%, respectively, and 48,06% and 52,6% in the local hypothermia group. Micrographs of H&E stained slices were photographed thorugh a bright field microscope and data extracted using UTSCSA Image Tool.The average thickness of non-hypothermic ischemic eyes (189,3 mm) was less than that of both ischemic hypothermic (234,8 mm) and untreated eyes (227,5 mm). On average the relative thickness of ischemic to untreated eyes was greater in hypothermic rats than non-hypothermic rats (90% and 67,3%, respectively).

Conclusions: Preliminary results indicate that local hypothermia has a protective effect during ischemia and reperfusion, induced by high intraocular pressure. This can be seen from histological examinations as well as ERG recordings.