Oxygen Saturation in Retinal Vessels in LTG During Flicker

Abstract

Purpose:: To measure oxygen saturation in retinal arteries and veins in normals and LTG patients during flicker provocation.

Methods:: The oxygen saturation in retinal arteries and veins vessels was examined by the Imaging Spectrometer (Jena). The estimation of the oxygen saturation OS2_arterial and OS2_venous of retinal vessels was based on the evaluation of different extinction spectra of hemoglobin and oxy-hemoglobin. The measurement of OS2_arterial and OS2_venous was performed before flicker, 30sec, 60 sec and 180 sec during provocation with flicker, and 360 sec after finishing flicker. The light provocation of the retina was performed 180 sec with a full-field luminance flicker with 10 Hz. We examined the effect of flicker in 23 eyes of 23 healthy subjects (mean age 42+-12 years) and 17 eyes of 17 patients with low tension glaucoma. For statistical analyses, the non-parametric Mann-Whitney-Wilcoxon test were performed.

Results:: The oxygen saturation in retinal arteries and veins (+- standard deviation) was before flicker in healthy eyes 93.2+- 1.6% (OS2_arterial), 58.7+-2.8% (SO2_venous), and 88.8+- 1.5% (OS2_arterial), 61.2+-3.4% (SO2_venous) in LTG eyes. During flicker the venous oxygen saturation SO2_venous decreased significantly by -5.3 % +- 2.1% in healthy eyes and by -3.4 % +- 1.9% in LTG eyes. 3 minutes after finishing flicker the venous oxygen saturation became normal (57.6+-1.9%) in healthy eyes and (60.2+-2.8%) in LTG eyes. The arterial oxygen saturation remained stable under flicker (94.0+-1.6% after 180 sec flicker) in normals and (89.6+-1.5% after 180 sec flicker) in LTG eyes.

Conclusions:: During flicker normal eyes showed a significant decrease of the venous oxygen saturation and an increase of the arterio-venous difference in retinal vessels. Measuring retinal oxygen saturation in retinal arteries and veins during flicker might be a new test to detect impaired regulation of the blood supply of the retinal ganglion cells during phases of increased neuronal activity.

Keywords: blood supply • retina • metabolism