Macular Retinal Oximetry Repeatability and its Relationship with Multifocal Electroretinography In Healthy Young Participants
Published 2022 by Jennyffer Smith
Co-Author(s): Kelly Bisignano, Wendy Harrison
Program Number: 220003
Article Type: Scientific Program
The purpose of this study was three-fold; to first determine the test-retest reliability of localized retinal oximetry measurements on the Zilia (Quebec, Canada) Oximeter Retinal Fundus Camera within healthy subjects 18-40 years of age, second, to evaluate the functional relationship between local oximetry and mfERG measures in the same location in this group, and lastly, to compare oxygen saturation across genders and ethnicities.
30 subjects were enrolled, but 27 subjects with complete data sets were analyzed. All had healthy retinas and at least 20/30 vision. Participants included 10 males and 17 females, with 2 black, 14 white, and 9 Asian, and 2 of other origin. Oximetry measurements were taken (300 um diameter) at four points 3.1 degrees from the fovea in the superior/temporal, superior/nasal, inferior/temporal, and inferior/nasal locations. Oximetry measurements were taken twice on the same day 20 minutes apart and then again 1-2 weeks later for both eyes starting with the right eye. An mfERG was performed using VERIS 6.4.3 with a stimulus near 100% contrast and 4-minute m-sequence using our common clinical technique and Burian-Allen electrode. Four hexagons corresponding to oximetry locations were evaluated individually, as well as averaged. P1 Amplitude (Amp) and implicit time (IT) in the right eye were evaluated. Oximetry was analyzed for repeatability with a repeated measures correlation for the same location between visits within the right eye, as well as a corrected T-test to evaluate the same oximetry locations between left and right eyes.
Average correlation coefficients for the three acquisition times across the 4 measures was 0.78 and 0.84, right and left eye respectively. Average oxygen saturation between eyes was not statistically different for acquisition 1, 2, and 3 (p = 0.57, 0.87, 0.47, respectively). A direct correlation was found between averaged oxygen saturation values and averaged mfERG hexagons (p = 0.036) such that as oxygen saturation increased, P1 Amp increased. No relationship was seen with averaged oxygen saturation and IT (p = 0.63). Significant differences were observed in Asian and Caucasian oximetry comparisons (p = 0.01), but not gender (p = 0.93).
This study is the first to evaluate macular oxygen saturation in healthy individuals as is correlates to mfERG metrics. The relationship between oxygen saturation and mfERG amplitude adds to our knowledge on the mfERG and retinal health. Test-retest for the Zilia oximeter has good repeatability for intersession measures, however, there is a learning curve, likely due to the brightness of the light, thus multiple measurements are needed per this data. Ethnicity differences were also found in retinal oxygen saturation, which requires further investigation with broader ethnic backgrounds.