Abstract
The light capturing properties of cone photoreceptors create the elementary signals that form the basis of vision. Variation in the amplitude of individual cone signals has been found physiologically as part of normal retinal circuit processing. Less well characterized is how cone signals may vary due to purely optical properties. We present a model of light propagation in cones using a finite difference beam propagation method to simulate how light from a small stimulus travels through a cone plus its immediate neighbors. The model calculates the amount of light absorbed in the cone outer segments, from which an estimate of the photoresponse can be made. We apply the method to adaptive optics microstimulation to find the optimum optical conditions that will confine the most light into a single cone in the human retina. We found that light capture is especially sensitive to beam size at the pupil and to the cone diameter itself, with the two factors having a complex relationship leading to sizable variation in light capture. Model predictions were validated with two types of psychophysical data. The model can be employed with arbitrary stimuli and photoreceptor parameters, making it a useful tool for studying photoreceptor function in normal or diseased conditions.
Highlights
Most of our day-to-day visual experience derives from signals that originate in cone photoreceptors
In this paper we present a waveguide model of cone photoreceptors that employs a finite difference beam propagation method (FDBP) [21,22,23]
Normal propagation is depicted in Fig. 3(C), with the beam centered on a photoreceptor, concentrating the light into the outer segment
Summary
Most of our day-to-day visual experience derives from signals that originate in cone photoreceptors. Recent experiments have shown that the functional weighting of each photoreceptor varies [1,2,3] Such variation will arise, in part, from differences in synaptic strength encountered as the signals flow through retinal circuits. As cones vary in size and shape, the efficiency of light propagation through them will vary from cone to cone, altering the amount of light absorbed by the photopigment It is unclear how much cone signal variation can be attributed to the biophysics of light capture versus downstream neural circuitry. It is not known under what conditions optimal light capture can be achieved in vivo, if one is to strive for stimulation of a single cone. To help resolve these ambiguities, we developed a model of light propagation and absorption within photoreceptors to be used as a tool to study such effects
Sign-in/Register to view highlights & summary 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.
