Photodynamic Treatment in a Rabbit Model of Glaucoma Surgery

Abstract

Abstract: : Purpose: To evaluate the safety and efficacy of verteporfin photodynamic treatment as an adjunct to glaucoma filtration surgery in pigmented and non-pigmented (albino) rabbits. Methods: Albino New-Zealand White (NZW, n=2) and pigmented Dutch-Belted (DB, n=21) rabbits underwent full thickness sclerectomy on one eye. The experimental group (group I, n=2NZW and n=7DB) underwent IV injection of verteporfin (2mg/kg) and subsequent photoactivation (689nm laser light) at the operative site on postoperative day 1 (POD1). Control groups of animals received either light exposure (group II, n=4) or verteporfin (group III, n=2), or no other intervention (group IV, n=2). Intraocular pressure (IOP) was measured with a pneumotonometer prior to (POD0) and daily thereafter for the first week after sclerectomy (POD1-POD7) and every other day for the second week (POD9, 11, 13, 15). NZW rabbits developed massive periorbital edema and IOP elevation on POD2. These animals were sacrificed at that time point and their eyes were not included in any further analysis. Percentage IOP reductions of the operated over the contralateral control eyes were compared among the various groups of DB rabbits using ANOVA. The success (percentage IOP reduction >15%) rate at POD15 was compared among the various groups using chi square test. Eyes were examined histologically for evaluation of fibrosis. Results:NZW rabbits developed extensive occlusion of the choriocapillaris with resulting massive choroidal hemorrhage. BD rabbits in the experimental group (group I) had mean (+SEM) percentage IOP reduction of 25.1% (+2.7) during the follow-up period. In contrast, groups II, III and IV had IOP reductions of 3.9% (+5.4), 12.2(+6.7) and 4.3(+6.0) respectively (p<0.005, ANOVA). Group I was statistically different from groups II and IV (p<0.05, Bonferoni post-hoc analysis) but not from group III (where n=2). Successful IOP reduction (of at least 15%) from the contralateral eye was achieved in 6 out of 7 experimental animals at POD15 while only in one out of 8 control animals (p<0.02, chi square test). Conclusions: Wound healing in glaucoma surgery may be successfully modulated post-operatively using photodynamic therapy. Albino animals have a higher rate of complications because of penetration of the laser light to deeper structures due to lack of pigment.

Keywords: photodynamic therapy • wound healing • intraocular pressure