9. Retinal Oximetry and Retinal Vein Occlusion

Einar Stefánsson, S. H. Hardarson, R. Karlsson, G. H. Halldorsson, T. Eysteinsson, J. A. Benediktsson, J. M. Beach (Reykjavík)

Purpose: A non-invasive study of the oxygen saturation of retinal venules in eyes with retinal vein occlusion (RVO) and how laser treatment affects the oxygen saturation.
Methods: Our automatic non-invasive retinal oximeter yields fundus images with 4 wavelengths of light simultaneously and calculates optical density ratio, which is linearly related to hemoglobin oxygen saturation (SO₂). We performed oximetry in 7 patients with RVO. We measured the healthy fellow eye, and retinal venules outside and inside the occluded area in the RVO eye before and after laser treatment. Differences were analyzed with two-way ANOVA and Bonferroni post tests and with a paired t-test.

Results: The venular SO2 was 59±6 % in healthy fellow eyes (mean±SD; n=5), 60±12 % in non-occluded areas of RVO eyes (n=4), 39±23 % before laser in occluded venules (n=5) and 56±4 % in occluded venules following laser treatment (n=5). Before laser the occluded venules have a significantly lower SO₂ than healthy eyes or nonoccluded areas of RVO eyes (p<0.05) and the SO₂ was normalized by laser treatment. In the 4 eyes measured both before
and after laser treatment the SO₂ rose from 38±26 % to 57±4 % (p= 0.24, paired t-test). The figure shows a pseudocolor SO2 map before and after laser treatment.
Conclusions: The automatic non-invasive retinal oximeter demonstrates decreased oxygen saturation in occluded retinal venules compared with healthy areas of the RVO eyes and healthy eyes. Laser treatment in RVO brings the oxygen saturation back to normal values.

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