Argon laser-assisted hypotony model in the rabbit

To investigate whether ocular hypotony formation with 360 degrees endocyclophotocoagulation is possible. Twelve male New Zealand White rabbits were used. Entire ciliary body epithelium was destructed with green laser photocoagulation after pars plana lensectomy and anterior vitrectomy in six rabbits. Endocyclophotocoagulation was not performed to the remaining six rabbits (control group). Intraocular pressure (IOP) was measured preoperatively and followed up everyday in the first week and weekly until the end of month one. All of the rabbits were sacrificed and ciliary bodies were left for gross and light microscopic examination. Mean baseline IOPs were similar in laser and non-laser group (14.8 ± 1.4 (range 12.2-17.3) vs 14.4 ± 1.4 (range 12.2-15.9), p = 0.650). Mean IOP was 6.6 ± 0.45 mmHg (range 5.9-7.1) in the laser group and 11.5 ± 1.2 mmHg (range 10.2-13.4) in the non-laser group in postoperative day 1. IOP was below 4 mmHg in all eyes on the second day and after in laser group. In the macroscopic evaluation, the entire ciliary body had a white (loss of pigmentation) and atrophic appearance in all of the eyes in the laser-treated group compared to non-laser group. In the laser group, light microscopic examination demonstrated a severe 360 degrees disruption of ciliary processes. Ciliary processes were covered with fibrin exudation consisting of fibroblasts. There was a mild inflammation with disruption or atrophy of ciliary body epithelium with cystic vacuolar degeneration. Three hundred sixty degrees endocyclophotocoagulation yielded severe ciliary epithelium damage. IOP reduction started very early and continued in hypotonic levels during follow up period.