INCREASE OF ENDOTHELIN-1 CONCENTRATION IN AQUEOUS-HUMOR INDUCED BY ARGON-LASER TRABECULOPLASTY IN THE RABBIT - A PRELIMINARY-STUDY

Purpose: To investigate the impact of argon laser trabeculoplasty (ALT ) on endothelin-1 (ET-1) concentration of aqueous humour and intraocul ar pressure (IOP) in the rabbit. Methods: Standard ALT was performed o n one eye of 19 pigmented rabbits. A modified treatment in which the l aser light was focused on the inner limbal surface (argon laser sclero plasty, ALS) was also performed on one eye of a further 15 rabbits. IO P was measured with a Tono-Pen-2 tonometer before treatment, under gen eral anaesthesia, Post-laser IOP measurements followed by aqueous humo ur aspiration were performed under general anaesthesia 4, 24 and 120 h ours after treatment. IOP readings were considered relative values, si nce the tonometer was calibrated to the human eye and not to the rabbi t eyeball. Different groups of animals were used for the tests after e ach time period. The groups of 4 hours time consisted of 9 animals whi ch had undergone ALT and 5 which had undergone ALS, All the other grou ps consisted of 5 animals each, Results: In the ALT group IOP decrease d following treatment, and the IOP change (a relative change) showed a significant difference between the treated and the control eyes at al l three follow-up times (paired t-test, p<0.05), and a significant int eraction was found between treatment and follow-up time (ANOVA, p<0.05 ), Concentration of ET-1 in the aqueous humour of the treated eyes inc reased by about an order of magnitude 4 hours after ALT, compared to t he contralateral control eyes (103.66 +/- 41.59 pg /ml versus 8.75 +/- 2.95 pg/ml, Wilcoxon matched pairs test, p<0.01), ET-1 concentration 24 and 120 hours after ALT, however, did not differ significantly from the corresponding contralateral control values. In the ALS group neit her IOP change nor aqueous humour ET-1 concentration differed in a sta tistically significant manner between the treated and control eves, Co nclusions: The results suggest that ALT is followed by an immediate an d short-term increase of aqueous humour ET-1 concentration in the rabb it, probably due to leakage from the uveal tissue.