Abstract
Purpose :
Developing biomarkers to non-invasively measure cellular function across the retina is critical for assessing ocular health and disease. Optoretinography quantifies cellular function in the living retina. Here, we investigate the population cone optoretinogram (ORG) versus retinal eccentricity in healthy subjects.
Methods :
Healthy subjects (N=5, 22-43 years) were imaged with an adaptive optics scanning laser ophthalmoscope (AOSLO, 785 nm, 1° x 1° field). At each of five retinal locations temporal to the fovea (1°, 2°, 4°, 8°, 16°) five sets of six consecutive videos were collected in randomized order, totaling 30 videos at each retinal location. Prior to each set, subjects were dark adapted for three minutes. Then, three videos were collected with no stimulus (control), followed by three videos with a stimulus (545Δ10 nm, 770 nW/deg2, 0.168 s exposure duration). Videos were registered and confocal intensities of individual cones were extracted, normalized and standardized. To compute the population ORG timecourse, the dispersion of the standardized cone intensities across time was calculated as previously described (Cooper et al., 2017). The peak amplitude of a smooth fit to the measured ORG timecourse was taken as the ORG amplitude.
Results :
The population ORG was measurable at each location for all subjects. When averaged across subjects, the ORG amplitude exhibited a decreasing trend with increasing eccentricty (5.22 a.u. ± 0.48 SEM at 1°, 4.68 ± 0.35 at 2°, 4.62 ± 0.44 at 4°, 3.31 ± 0.54 at 8°, and 3.09 ± 0.56 at 16°). A two-way ANOVA (Eccentricity and Subject) showed a significant main effect of eccentricity [F (4,24) = 14.87, p < 0.001] and subject [F (4,24) = 9.28, p < 0.001]. All subjects exhibited lower ORG amplitudes at both 8° and 16° relative to 1°, 2°, and 4°.
Conclusions :
The population ORG amplitude decreases with eccentricity. This may be due to differences in cone outer segment morphology at different retinal locations. Characterizing the ORG as a function of eccentricity in healthy subjects is an important step towards establishing norms that will allow it to be used as a biomarker for assessing visual function.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.