Abstract
Purpose :
Oxygenation of the eye involves a complex interaction between systemic vasculature and blood pressure, intraocular pressure (IOP), localized vascular controls, and individual cellular function. Key changes take place at the level of the microvasculature in retinal pathology. A better understanding of the retinal oxygenation surrounding the foveal avascular zone will provide key information regarding normal physiology and early disease changes. The purpose of this study was to investigate diurnal variations in retinal oximetry and evaluate its relationship with other systemic and ocular measurements.
Methods :
Participants (n=18, mean age 27 ± 5.50 years) with normal ocular health were recruited. Systemic blood pressure, pulse, IOP, biometry, and retinal oximetry were measured and OCT images were captured for the right eye every four hours over 24 hours. Participants were in darkness from 11:00 PM to 7:00 AM. Prior to the first time point, the right eye was dilated with 1% atropine. Thicknesses of the retina and choroid over a 1 mm diameter were determined. Repeated measures ANOVA with multiple regression analysis compared ocular and systemic metrics across time points. Amplitude of change over 24 hours and phase relationships were determined.
Results :
Systemic parameters exhibiting diurnal variation included heart rate and systolic blood pressure (p<0.05). Pulse oximetry, diastolic blood pressure, and mean arterial pressure did not exhibit significant diurnal variation. Ocular parameters demonstrating significant diurnal variation included IOP, axial length, choroidal thickness, retinal thickness, and retinal oximetry (p<0.05). Amplitude of retinal oximetry diurnal variation (3.82 ± 0.64 %) was in-phase with IOP variation (3.31 ± 0.47 mmHg) and choroidal thickness variation (10.85 ± 2.02 μm), all peaking at the 4:00AM time point. These ocular rhythm amplitudes were antiphase to axial length (20.0 ± 2.66 μm) and retinal thickness variations (5.36 ± 1.06 μm).
Conclusions :
This study is the first to show that diurnal variation exists in the oxygenation of retinal tissues over 24 hours. The diurnal rhythms observed in retinal oxygenation related to various ocular and systemic diurnal rhythms.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.