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Keywords:

  • hypoxia;
  • ischaemia;
  • oximetry;
  • oxygen saturation;
  • retina;
  • retinal vein occlusion

Abstract.

Purpose:  The aim of this study was to test whether oxygen saturation in retinal blood vessels is affected by branch retinal vein occlusion (BRVO).

Methods:  The spectrophotometric retinal oximeter is based on a fundus camera. It simultaneously captures images of the retina at 586 and 605 nm and calculates optical density (absorbance) of retinal vessels at both wavelengths. The ratio of the two optical densities is approximately linearly related to haemoglobin oxygen saturation. Relative oxygen saturation was measured in retinal blood vessels in 24 patients with BRVO. Friedman’s test and Dunn’s post test were used for statistical analyses.

Results:  Oxygen saturation in occluded venules ranged from 12% to 93%. The median oxygen saturation was 59% (range 12–93%, n = 22) in affected retinal venules, 63% (23–80%) in unaffected venules in the BRVO eye and 55% (39–80%) in venules in the fellow eye (p = 0.66). Corresponding values for arterioles were 101% (89–115%, n = 18), 95% (85–104%) (p < 0.05) and 98% (84–109%).

Conclusions:  Venular saturation in BRVO is highly variable between patients. Hypoxia is seen in some eyes but not in others. This may reflect variable severity of disease, degree of occlusion, recanalization, collateral circulation, tissue atrophy, arteriovenous diffusion or vitreal transport of oxygen.