Higher Degree of Safety in Fractionated Cyclophotocoagulation: Experimental Implications

Abstract

Purpose: : Cyclophotocoagulation has been reported to be associated with severe complications such as persisting hypotonia. Thus it might be an option to apply a reduced number of effects initially and repeat the treatment after an interval with a smaller number of effects if no sufficient reduction of IOP has been achieved. This concept is termed by the authors as fractionated cyclophotocoagulation. The aim of the study was to investigate if there is a difference between a single session and fractionated treatment regarding IOP reduction and complication rate.

Methods: : Wild type pigmented rabbits were treated with different numbers of cyclophotocoagulation effects. Each effect was performed with energy between 3 and 4 Joule (2W, 1.5 – 2s) minimizing pop effects. 6 rabbits were subjected to a four–step fractionated treatment with a total of 30 effects (5–5–10–10 effects; interval of 1 week between each session). 5 rabbits were treated with 30 effects in a single session. Intraocular pressure was measured using a Tonopen® XL before and one week after treatment. The outcome was compared using an unpaired t–test (double sided).

Results: : 6 rabbits received 30 effects in a single session. One rabbit developed persisting hypotonia after surgery. 3 rabbits had anterior chamber bleeding, one a severe non resorbing hemophthalmus with subsequent and permanent rise of IOP to approx. 40 mmHg. Excluding the latter animal, the other 5 animals showed an IOP drop from 14.2 ± 0.5 mmHg to 8.4 ± 1.4 mmHg (p=0.005). 6 rabbits received fractionated treatment and IOP was reduced in these animals from 13.2 ± 0.3 mmHg to 9.8 ± 1.2 mmHg (p=0.028). Only in one animal a transient anterior chamber bleeding occurred.

Conclusions: : The IOP reduction in the non–fractionated group tends to be only marginally higher than in the fractionated group. On the other hand the complication rate appears to be lower in the fractionated group. This suggests that a comparable IOP reduction can be achieved by using a fractionated schedule for cyclophotocoagulation treatment combined with a higher degree of safety.

Keywords: ciliary body • intraocular pressure • aqueous