Dose–Response Relation of Cyclophotocoagulation in an Animal Model

Abstract

 

Purpose:

 

Cylophotocoagulation is used frequently to lower intraocular pressure (IOP) in end stage glaucoma patients. Up to now it is not clear whether there is a correlation between the applied number of laser effects and the IOP lowering effect in terms of a dose–response curve.

 

Methods:

 

Wild type pigmented rabbits were treated with different amounts of single cyclophotocoagulation effects. Each effect was performed with energy between 3 and 4 Joule (2W, 1.5 – 2s). 27 rabbits were distributed into 5 groups and were treated with 1, 5, 10, 20 and 30 effects respectively. IOP was measured by Tonopen XL and the pressure before and one week after the treatment was compared using a paired and unpaired t–test (double sided) where applicable.

 

Results:

 

Tabel 1 shows the results of IOP in mmHg. A statistically significant IOP reduction is marked with a asterisk. IOP reduction was compared between 1 and 5, 5 and 10, 10 and 20, 20 and 30 effects and statistically significant differences are marked with a #.

 

Conclusions:

 

There is no distinct dose–response relation between IOP and applied number of cyclophotocoagulation effects. According to our results the first few effects have the most important impact on IOP, whereas a larger number of effects seem to be partially compensated in these healthy animals.  

 

Keywords: intraocular pressure • aqueous • ciliary body