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Dorzolamide-Timolol Combination and Retinal Vessel Oxygen Saturation in Patients with Glaucoma or Ocular Hypertension
  1. Sindri Traustason (sindri{at}halur.net),
  2. Sveinn Hakon Hardarson (sveinnha{at}gmail.com),
  3. Maria Soffia Gottfredsdottir (mariago{at}landspitali.is),
  4. Thor Eysteinsson (thoreys{at}hi.is),
  5. Robert Arnar Karlsson (rak{at}oxymap.com),
  6. Einar Stefánsson (einarste{at}landspitali.is),
  7. Alon Harris (alharris{at}iupui.edu)
  1. University of Iceland, Iceland
  2. University of Iceland, Iceland
  3. Landspitali - University Hospital, Iceland
  4. University of Iceland, Iceland
  5. University of Iceland, Iceland
  6. University of Iceland, Iceland
  7. Indiana University School of Medicine, United States

    Abstract

    Aims: 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. 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.

    Conclusion: Adding dorzolamide to timolol monotherapy has minimal effect but going from dorzolamide-timolol combination to timolol alone lowered arteriolar and venular oxygen saturation. The retinal oxygen saturation measurements show 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.

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