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Benjamin Lochocki, Brian Vohnsen, ; Single Beam Frequency Flickering Analysis of the Stiles-Crawford Effect of the First Kind. Invest. Ophthalmol. Vis. Sci. 2014;55(13):777.
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The photoreceptors are the last optical elements of the eye that connect the retinal image to neural responses following absorption. Therefore, studying the function of the retina plays a key role to enhance understanding of the visual process and for further development of eye modeling. This study is aimed at examining the temporal responses of cone photoreceptors using a flickering single beam Maxwellian view setup at different frequencies.
The Stiles-Crawford effect (SCE) of the first and second kind are commonly analysed using a constant reference beam and a separated path for a tuneable traversing probe beam when determining subjective visibility. Here, a compact single beam flickering system with tuneable crystal filters for wavelength and brightness control in conjunction with two galvanometric scanning mirrors has been developed. This automated approach allows individual defocus correction at any wavelength and scanning across the full pupil along a line at any angle in the pupil plane and at various flicker frequencies.
The experimental results confirm an impact of frequency on the directionality of the SCE for all subjects which can be related to the response time of the visual pigments. The determined directionality at low frequencies is reduced whereas at higher frequencies the directionality agrees well compared to a bipartite field setup. Additionally, we analysed and compared our obtained data for the hue shift of the SCE of the second kind to previous studies.
Using the methodology, we are able to explore photoreceptor directionality and the temporal responses of the cone pigments in a novel way, giving insight into photoreceptor alignment and vision for improved optical design. The chosen methodology allows also examination of any transient SCE by sequentially entering the eye pupil at opposite sites from the point of maximum visibility.
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