July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Characterizing the Stiles-Crawford effect of the first kind at foveal and parafoveal regions using a digital micromirror device
Author Affiliations & Notes
  • Alessandra Carmichael Martins
    School of Physics, University College Dublin, Dublin, Ireland
  • Brian Vohnsen
    School of Physics, University College Dublin, Dublin, Ireland
  • Footnotes
    Commercial Relationships   Alessandra Carmichael Martins, None; Brian Vohnsen, None
  • Footnotes
    Support  H2020 ITN MyFUN grant agreement no. 675137
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 4052. doi:
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      Alessandra Carmichael Martins, Brian Vohnsen; Characterizing the Stiles-Crawford effect of the first kind at foveal and parafoveal regions using a digital micromirror device. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4052.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The purpose of this study is to analyse the Stiles-Crawford effect of the first kind (SCE-I) both for the foveal and parafoveal regions. This is important as both foveal and peripheral vision can impact eye growth and thus myopia progression. The analysis will determine cone photoreceptor light acceptance at up to 7.5° eccentricity and will be compared to a geometrical light acceptance model of the photoreceptors.

Methods : A uniaxial flicker system has been implemented using a Digital Micromirror Device (DMD) to flicker between a 2.3 visual degrees circular reference and scanning test patterns in a monocular Maxwellian view at 0.5 Hz. Brightness of the test field is adjusted by the duty cycle of the DMD to an upper limit of 22.7 kHz. A total of 4 series for 11 entrance points along the horizontal axis have been realized for 8 emmetropic subjects whose pupils have been dilated with tropicamide. Measurements were taken at 2.5, 5 and 7.5o nasal and 2.5 and 5o temporal retina by use of a fixation LED, and with 450, 550 and 650nm light set by a tuneable liquid-crystal filter. Visibility data have been fitted to a Gaussian SCE-I distribution characterized by the point of maximum visibility and a characteristic directionality parameter (ρ).

Results : The SCE-I directionality parameter at the fovea was found to be 0.044±0.010mm-2 in green light when averaged for all subjects. Similar values were found at 450nm, whereas a 12% increase was measured at 650nm. Furthermore, a decrease with retinal eccentricity for all 3 wavelengths was noted. Variations measured at 550nm were most prominent, reduced by 37% at 5o and 52% at 7.5o nasal, and obtaining comparable values to those at temporal retina. In turn, only a slight nasal offset was noted for the point of maximum visibility with increasing eccentricity. This tendency is reproduced in numerical simulations for the light acceptance of the cone photoreceptors.

Conclusions : Results shows a marked reduction by up to 52% for all subjects of the directionality parameter from the fovea to the parafoveal region. The results conform well to the theoretical expectations based on a geometrical light acceptance model of the foveal and parafoveal cones.

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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