Abstract
Purpose: :
The study addresses the unsolved problem of the relationship between number of laser burns of cyclophotocoagulation (CPC) and reduction of intraocular pressure (IOP).
Methods: :
Thirty Chinchilla Bastard rabbits were distributed into five groups and were treated either with 1, 5, 10, 20 or 30 CPC burns. IOP was followed for 1 week. IOP-lowering effects of a single-session treatment with 30 laser burns were compared with those of a fractionated treatment in which 30 laser burns were applied in three sessions of 10 CPC burns each given at 1-week intervals (N=6 per group). IOP was followed for 7 weeks. To elucidate the role of prostaglandins as a mediator of CPC effect, the IOP reduction of a dorzolamide and travoprost treatment administered post-CPC was investigated (N=6).
Results: :
IOP decreased with an increasing number of CPC burns in a non-linear fashion up to -6.1 ± 1.4 mmHg after 30 burns. Fractionated and single-session treatment groups showed comparable mean IOP reductions (-3.0±0.3 vs.-3.8±0.9mmHg), but there were fewer complications and more constant results in the fractionated group. Dorzolamide had a stronger IOP-reducing effect than travoprost after CPC (15.3 ± 0.6 vs. 16.6 ± 0.7 mmHg; p=0.036).
Conclusions: :
The study reveals a complex relationship between IOP reduction and the number of CPC burns; the IOP reduction per CPC burn decreases the more CPC burns were applied. Fractionated CPC gives comparable IOP reduction at a higher degree of safety. IOP reduction with travoprost is weakened after CPC, which implies that prostaglandins may mediate the CPC effect.
Keywords: ciliary body • intraocular pressure • trabecular meshwork