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Brian Vohnsen, Diego Rativa Millan, Carmen Vela, Benjamin Lochocki, Philip Kruger; The role of defocus on photoreceptor light coupling analyzed with a waveguide-based retinal simulator. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3429.
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© ARVO (1962-2015); The Authors (2016-present)
Obliqueness of light at the retina diminishes the visual response as a consequence of the Stiles-Crawford effect caused by photoreceptor waveguiding. The aim of this study is to analyze the sensitivity to defocus under waveguide conditions that resemble those of the human eye retina using a retinal simulator consisting of an array of photonic-crystal waveguides.
A liquid-filled photonic crystal fibre array has been used to simulate waveguiding by retinal photoreceptors and the total fraction of coupled light has been measured. Defocus is generated with a Badal-system and monitored simultaneously with a Hartmann-Shack wavefront sensor. Measurements are performed both at 633 nm and at 543 nm wavelength to study a possible chromatic impact. The results are compared with those of an analytical waveguide model and Zemax-based eye models.
Measurements show that the fraction of coupled light power is sensitive to defocus as expected due to the wavefront curvature at the entrance facet of the waveguides. This is in agreement with the numerical models suggesting a possible role of light power for accommodation and emmetropization of the eye.
We found that a photonic crystal fibre array is a suitable experimental tool to analyze the role of defocus and more generally aberrations and their possible role on vision and effective retinal images. The fraction of light that couples to waveguide modes may provide a clue for accommodation and emmetropization of the eye. The sign of defocus is not determined but may relate to the chromatic difference for a finite bandwidth or to photoreceptor disarray though also other aberrations and other factors can provide accommodative clues.
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