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O. Zeitz, M. Klemm, H. Schwarzer, G. Richard, L. Wagenfeld; Relation of Number of Laser Burns and IOP-Reduction in Cylcophotocoagulation: An Animal Study. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2005.
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The study addresses the unsolved problem of the relationship between number of laser burns of cyclophotocoagulation (CPC) and reduction of intraocular pressure (IOP).
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).
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).
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.
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