Dorzolamide-timolol combination and retinal vessel oxygen saturation in patients with glaucoma or ocular hypertension.
OBJECTIVE
To examine whether the addition of dorzolamide to timolol monotherapy influences oxygen saturation in the human retina.


METHODS
Non-invasive spectrophotometric retinal oximetry was used to measure oxygen saturation in retinal vessels. Twenty patients with open-angle glaucoma (11) and ocular hypertension (9) were recruited. The patients were randomised into receiving timolol monotherapy or dorzolamide-timolol combination for an 8-month test period, followed by a second test period, before which the patients switched treatments. Oximetry measurements were performed at 2-month intervals during each period. Of the 20 patients, 13 followed the study protocol into the second test period, and 10 managed all study visits.


RESULTS
The oxygen saturation in retinal vessels was stable within the test periods. The mean arteriolar saturation was 96 (2)% (mean (SD)) during timolol monotherapy and 97 (2)% during dorzolamide-timolol combination therapy (p = 0.17, all patients pooled, n = 13). Corresponding values in venules were 66 (5)% during timolol monotherapy and 65 (6)% during dorzolamide-timolol therapy (p = 0.13). Patients who started on dorzolamide-timolol combination showed a significant reduction in arteriolar (98 (2)% to 95 (2)%, p<0.01) and venular saturation (69 (5)% to 66 (6)%, p<0.05) when changing to timolol monotherapy.


CONCLUSIONS
Adding dorzolamide to timolol monotherapy has a minimal effect, but going from dorzolamide-timolol combination to timolol alone lowered arteriolar and venular oxygen saturation. The retinal oxygen saturation measurements show a high degree of stability over an extended period of time. Previous studies have suggested increased retinal and optic nerve blood flow with dorzolamide. Unchanged oxygen saturation and increased blood flow would indicate increased oxygen delivery to the retina.
Department of Ophthalmology, University of Iceland, Reykjavik, Iceland.
S
S
Traustason
S H
SH
Hardarson
M S
MS
Gottfredsdottir
T
T
Eysteinsson
R A
RA
Karlsson
E
E
Stefánsson
A
A
Harris
D000293:Adolescent; D000328:Adult; D000368:Aged; D000959:Antihypertensive Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects; D004311:Double-Blind Method; D004338:Drug Combinations; D005260:Female; D005902:Glaucoma, Open-Angle / Q000097:blood / Q000188:drug therapy; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000097:blood* / Q000188:drug therapy; D010092:Oximetry / Q000379:methods; D010100:Oxygen / Q000097:blood*; D012171:Retinal Vessels / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology* / Q000627:therapeutic use; D013876:Thiophenes / Q000494:pharmacology* / Q000627:therapeutic use; D013999:Timolol / Q000494:pharmacology* / Q000627:therapeutic use; D055815:Young Adult
D000959:Antihypertensive Agents; D004338:Drug Combinations; D013449:Sulfonamides; D013876:Thiophenes; C479140:dorzolamide-timolol combination; D013999:Timolol; D010100:Oxygen