Abstract
Purpose :
To investigate regional dependence of retinal pigment epithelium (RPE) organelle motility in healthy human eyes across the macula.
Methods :
Three healthy participants (S1-S3) were imaged with the FDA 1060 nm 3.4 MHz Fourier-domain mode-locked-adaptive optics – optical coherence tomography (AO-OCT) system. 2°×2° field of view AO-OCT volumes were collected from the fovea to 12° temporal retina in steps of 1.5° (9 total locations), with the system focus set to the photoreceptor (PR)-RPE complex. At each retinal location, three 10 s videos (20 volumes/video; 0.5 s interval) were acquired to capture the organelle motility speckle decorrelation. Postprocessing included registration of the AO-OCT volumes to reference volumes selected from each of the three video recordings and manual selection of RPE cells. The temporal decorrelation function of each RPE cell, defined by a Voronoi patch, was calculated and normalized to the PR which has a relatively stable temporal correlation. Organelle motility was characterized as the time constant of the fitted exponential decay function to the decorrelation curve.
Results :
The RPE cell mosaics were resolved in all locations of the three subjects. The exponential fit to the decorrelation function resulted in average time constants of 6.6 ± 0.9, 7.1 ± 0.8, and 9.2 ± 1.8 s across the macula in S1, S2, and S3, respectively. While the average decay time constant differed between subjects, for subjects S1 and S2, the variation in the estimated values across the macula was small. Subject S3 exhibited the highest variation, which was primarily caused by the higher estimated decay time at the fovea compared to other locations.
Conclusions :
RPE organelle motility can be characterized as the time the speckle field takes to decorrelate using high speed AO-OCT. The results in healthy participants indicate low variability in RPE organelle motility across the macula. As diseased RPE cells have been shown to exhibit abnormal organelle motility, we expect that future investigations on diseased eyes will reflect changes in the measured time constant at affected regions. Further investigations on a larger group of healthy subjects will establish a normative baseline for the adoption of RPE organelle motility as a clinically relevant functional biomarker of retinal degenerative diseases.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.