LOCAL HYPOTHERMIA PROTECTS THE RETINA FROM ISCHEMIC-INJURY IN VITRECTOMY

Aims-Hypothermic irrigating solutions were used during vitrectomy in p ressure induced ischaemic eyes so that their effects on retinal functi on and histological changes could be investigated. Methods-After anaes thetised albino rabbits underwent closed vitrectomy, their vitreous ca vities were continuously irrigated for 30 minutes at a perfusion press ure of 140 mm Hg. The rabbits were divided into three groups according to their intraocular perfusion temperatures-8 degrees C, 22 degrees C , and 38 degrees C. Electroretinograms were taken before and after irr igation. Glutamate levels in the vitreous were examined after irrigati on. Eyes were enucleated on the seventh postoperative day and examined histologically. Results-On the seventh postoperative day, the recover y rate of a-wave amplitudes was significantly lower in the 38 degrees C group than in the 8 degrees C group, and that of b-wave amplitudes w as significantly lower in the 38 degrees C group than in either the 8 degrees C or 22 degrees C group. Retinal damage in the 38 degrees C gr oup revealed more severe histological impairment than in either the 8 degrees C or 22 degrees C group. Oedema of the inner retinal layer was significant in both the 22 degrees C and 38 degrees C groups. Glutama tes reached peak values 30 minutes after the end of ischaemia in the 3 8 degrees C group. However, no significant glutamate increases were de tected 15 to 60 minutes after ischaemia in either the 8 degrees C or 2 2 degrees C group. Conclusion-Local hypothermia during vitrectomy in a cute ischaemic eyes appears to decrease retinal damage.