Experimental Eye Research 1997. december [antikvár]

d Exp. Eye Res. (1997) 65, 733-738 @ Protective Effects of Local Hypothermia in Vitrectomy Under Fluctuating Intraocular Pressure KAZUSHI TAMAI*, EIJI TOUMOTO and AKIO MAJIMA Department of Ophthalmology. Nagoya City University Medical School, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467, Japan (Received Lund 26 February 1997 and accepted in revised form 2 July 1997) 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 PGE3 concentrations 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. © 1997 Academic Press Limited Key words: local hypothermia: intraocular pressure: fluctuation; vitrectomy: blood-retinal barrier: electroretinogram; retina. 1. Introduction Intraocular pressure (IOP) during closed-system surgical procedures has been proved to vary greatly (Honda et al., 1982; Moorhead and Armeniades, 1986). The actual IOP can transiently exceed 100 mmHg in routine surgical procedures, including incision and suturing (Honda et al 1982). In vitreous surgery, various factors affecting IOP include bottle height, lumen sizes, suction forces and wound leak (Charles, 1987). Furthermore, the elevation of a perfusion bottle to inhibit intraocular bleeding is common in vitreous surgery (Michels, 1981). Breakdown of the blood-aqueous barrier (BAB) is frequently seen when IOP is elevated to 60-80 mmHg (Davson and Huber, 1950), and catastrophic falls in IOP also induce the breakdown of BAB (Davson. 1984). Therefore, large fluctuations of IOP during ocular surgery are likely to produce severe postoperative inflammation. The application of local hypothermia in vitreous surgery has recently been investigated (Rinkoff et al., 1986; Jabbour, Schepens and Buzney, 1988; Zillis, Chandler and Machemer, 1990; Hirose et al., 1992; Tamai et al., 1995a, 1995b, 1996), and we found it effective in reducing postoperative inflammation under * Address correspondence to: Kazushi Tamai. Department of Ophthalmology, Nagoya City University Medical School, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467. fapan. 0014-4835/97/120733+06 $25.00/0/ey970386 normal IOP (Tamai et al., 1995a). However, the most appropriate temperature for intraocular solutions has not been determined yet. In this study, we performed intravitreous irrigation under wide-ranging fluctuations of IOP using different hypothermic solutions, and measured the degree of BAB breakdown. We also examined the electrophysiologic and histologic changes of the eyes. 2. Materials and Methods All investigations involving animals conformed to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Vitrectomy and Subsequent Vitreous Perfusion Fifty-one albino rabbits were anesthetized with intravenous injections of 20 mg kg-1 of pentobarbital and intramuscular injections of 5 mg kg-1 of ketamine hydrochloride. Their pupils were dilated with a 1:1 mixture of 0-25% tropicamide and 5 % phenylephrine. Conjunctival peritomy was performed on one eye of each animal. A 500 ml bottle of intraocular irrigating solution (BSS plus, Alcon, Fort Worth, TX, U.S.A.) was suspended about 100 cm above eye level, and connected to a 20-gauge infusion cannula through a 400-cm-long tube. The cannula was inserted through the sclerotomy in the inferonasal quadrant 1-5 mm posts 1997 Academic Press Limited