Abstract
Purpose: :
To compare the effect of travoprost 0.004% and latanoprost 0.005% on choroidal blood flow and retinal vascular diameter in glaucoma patients.
Methods: :
After washout of current topical medication, intraocular pressure (IOP) in both eyes (Goldmann applanation tonometry), choroidal blood flow (laser Doppler flowmetry) and retinal vessel diameter (Retinal Vessel Analyzer) in one randomly selected eye were measured at baseline, after two weeks and after 4 weeks of treatment with travoprost or latanoprost, in a randomized, double masked, 2–way cross–over study in 20 open angle glaucoma patients. Results were analyzed in a two by three ANOVA model.
Results: :
After a 4 week treatment period, latanoprost reduced IOP from (mean ± SD) 19.6 ± 3.5 to 15.2 ± 3.2 mmHg and from 21.0 ± 5.0 to 15.2 ± 3.6 mmHg in the right and the left eyes respectively, while travoprost reduced IOP from 19.1 ± 3.7 to 15.7 ± 2.5 mmHg and from 20.6 ± 4.9 to 15.9 ± 3.7 mmHg in the right and the left eyes respectively. While IOP reduction was significant for both eyes (p<0.0001), the effect was comparable with both substances (p=0.21 and p=0.18 for the right and the left eyes respectively). Perfusion pressure in the experimental eye increased in average by 6.1 ± 7.2% (p=0.003). While choroidal blood flow seemed to remain stable (p=0.58), retinal arterioles showed a tendency to constrict by 2.4 ± 3.5% (p=0.029), latanoprost and travoprost showing a comparable effect (p=0.63).
Conclusions: :
Prostaglandin analogues may induce a mild retinal arteriolar constriction in some glaucoma patients. Because the expected decrease in blood flow of approximately 9.3% with an arteriolar constriction of 2.4% is very close to the expected increase in blood flow of 6.1% due to the observed increase in ocular perfusion pressure, the observed arteriolar response may simply represent an autoregulatory response.
Keywords: blood supply • pharmacology