Abstract
Using adaptive optics imaging tools to image the living retina, numerous investigators have reported temporal fluctuation in the reflectivity of individual cone photoreceptors. In addition, there is cone-to-cone (spatial) variation in reflectivity. As it has only recently become possible to image the complete rod photoreceptor mosaic in the living human retina, we sought to characterize the reflectivity of individual rods and compare their behavior to that of foveal/parafoveal cones. Across two subjects, we were able to successfully track the reflectance behavior of 1,690 rods and 1,980 cones over 12 hours. Rod and cone photoreceptors showed similar regional and temporal variability in their reflectance profiles, suggesting the presence of a common governing physiological process. Within the rod and cone mosaics, there was no sign of spatial clumping of reflectance profile behavior; that is, the arrangement of cells of a given archetypal reflectance profile within the mosaic was indistinguishable from random. These data demonstrate the ability to track the behavior of rod reflectivity over time. Finally, as these and other reflectance changes may be an indicator of photoreceptor function, a future extension of this method will be to analyze this behavior in patients with rod photoreceptor dysfunction (e.g., retinitis pigmentosa, Usher’s syndrome, and congenital stationary night blindness).
Highlights
In examining the first direct in vivo images of the human cone mosaic, one of the more salient features of the appearance of individual cone photoreceptors is that they vary considerably in their reflectance [1,2]
Regardless of the adaptive optics (AO) imaging modality used, similar regional variation in the appearance of cones has been seen in the corresponding in vivo images of the cone mosaic [5,6,7,8,9,10,11,12,13]
By measuring the StilesCrawford effect of individual cones using an AO fundus camera, it was shown that this spatial variability is not caused by cone-to-cone differences in directional tuning [12,13]
Summary
In examining the first direct in vivo images of the human cone mosaic, one of the more salient features of the appearance of individual cone photoreceptors is that they vary considerably in their reflectance [1,2]. Besides exhibiting variability in reflectivity between different cones, individual cones vary in their reflectivity over time, on scales ranging from seconds to hours [13,14,15]. These changes occur both in the presence and absence of a stimulus, and it has been suggested that these changes reflect physiological activity within the photoreceptor. The clinical applications of such measurements could be substantial; with the ability to monitor cone structure and function, researchers would be positioned to elucidate more clearly the disease sequence of retinal degenerations, and provide additional tools for assessing therapeutic efficacy in individuals receiving intervention
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
