Protective Effects of Local Hypothermia in Vitrectomy Under Fluctuating Intraocular Pressure

The effects of local hypothermia on the blood-aqueous barrier and retina were investigated in experimental vitrectomy under wide-ranging fluctuations of intraocular pressure.After anesthetized albino rabbits had undergone closed vitrectomy, their vitreous cavities were continuously irrigated for 60 minutes. Perfusion pressures were fluctuated alternately between 10 and 80 mmHg. The rabbits were divided into two groups in accordance with their intraocular perfusion temperatures: 8°C and 22°C. Electroretinograms were taken both before and after the irrigation. Protein and prostaglandin E₂(PGE₂) concentrations in the aqueous humor were measured on the 1st and 7th postoperative days. Histologic examination was performed on the eyes enucleated on the same days.There were no significant differences in either a- or b-wave amplitudes between the 8°C and 22°C groups. Both aqueous protein and PGE₂concentrations were significantly higher in the 22°C group than in the 8°C group on the 1st postoperative day. Histologically, the ciliary body showed remarkably more stromal edema in the 22°C group than in the 8°C group. The severity of the retinal damage did not seem to differ between the two groups.Local hypothermia during vitrectomy under fluctuating intraocular pressure inhibits the breakdown of the blood-aqueous barrier in the early postoperative stages.