Directional light-capture efficiency of the foveal and parafoveal photoreceptors at different luminance levels: an experimental and analytical study

Abstract

A gradual drop in visibility with obliquely incident light on retinal photoreceptors is namely described by the Stiles-Crawford effect of the first kind and characterized by a directionality parameter. Using a digital micromirror device in a uniaxial flicker system, here we report on variations of this effect with luminance levels, wavelengths within the visible and near-infrared spectrum and retinal regions ranging from the fovea to 7.5° parafoveal. Results show a consistent directionality in mesopic and photopic conditions. Higher directionality is measured for longer wavelengths, and a decrease with retinal eccentricity is observed. Results are discussed in relation to an absorption model for the visual pigments taking the outer-segment packing and thickness of the neural retina into account. Good correspondence is found without enforcing photoreceptor waveguiding.

Subjective measurement of the Stiles‐Crawford effect of the first kind with variation in accommodation

“…Directionalities in the present study were compared with those in other studies using a range of techniques. 6,15,16,33,34 The means of the studies had a 1.6 times range, with the mean for the present study falling in the middle of this range (Table 1). Applegate and Lakshminarayanan 33 Two-channel Maxwellian system using LEDs 0.050 ± 0.013…”

“…Lochocki and Vohnsen 34 Uniaxial system, galvanometric scanning mirrors 0.031 ± 0.003 Carmichael Martins and Vohnsen 16 Uniaxial system, digital micromirror device 0.044 ± 0.010 Present study Uniaxial system, spatial light modulator 0.039 ± 0.005…”

“…The SCE-I can be measured using subjective 1,6,7 and objective techniques, [8][9][10] but the directionality reported using the latter method is approximately twice that of the former technique due to the double-passage of light through the photoreceptors. [11][12][13] Various factors influence the directionality and peak location, such as wavelength, [14][15][16] luminance, 16,17 eccentricity 16,18,19 and ocular conditions such as ocular disease, [20][21][22] phototropism, [23][24][25] refractive errors, 6,7 aberrations 6,7 and accommodation. 6,26 Accommodation induced retinal stretching affects photoreceptor alignment and directionality.…”

The impact of aberrations in a 3D retinal model eye

“…The obliqueness of the wavefront at the retina is the cause of the SCE-I determined with Maxwellian light. [2][3][4][5][6][7][8][9][10][11] It also explains the presence of the SCE-II due to cross-coupling between adjacent but different cone types.…”

“…In consequence, even and odd-ordered Zernike aberrations of the eye are affected differently by the Stiles-Crawford effect of the first kind (SCE-I) that relates to obliqueness of light at the retina. [2][3][4][5][6][7][8][9][10][11] In this study, even and odd-ordered Zernike aberrations are studied individually with a simplified eye model to determine the impact of wavefront obliqueness in the retinal plane.…”