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Andrew J Zele, Beatrix K. Feigl, Prakash Adhikari, Dingcai Cao; Melanopsin contributions to image forming vision in humans. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5036. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To study human visual processing initiated by melanopsin photoreception. Melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGC) signal to non-image forming processes for circadian photoentrainment and control of the pupil light reflex, whereas melanopsin contributions to human vision are largely unknown.
Melanopsin, rod and the three cone photoreceptor excitations were independently controlled using a custom-built, Maxwellian view, 5-primary photostimulator (30° diameter circular field with the central 10.5° blocked; 2000 Td adaptation level). Observer calibrations minimised the effect of individual differences in pre-receptoral filtering. The intrusion of signal artefacts from penumbral cones in the shadow of retinal blood vessels was limited through application of temporal white noise.
We demonstrate that melanopsin-mediated image forming vision corresponds to an opponent S-OFF L+M-ON response property, with a low pass temporal contrast response and an average temporal resolution up to ~5 Hz. Incremental thresholds for the putative melanopsin isolating condition (rod and cone silenced) were more than 10x higher than for red-green colour vision. Cone-mediated visual discrimination thresholds improved in the presence of a melanopsin pedestal (17% Weber contrast).
Melanopsin photoreception may give rise to salient visual percepts in humans. These melanopsin signals are subtler than those originating in the cone photoreceptors and might have important roles for modulating vision mediated via rods and cones. With a capacity for signalling colour and integrating slowly changing lights, melanopsin-containing cells maybe the fifth photoreceptor for peripheral vision.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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