July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
Impact of pupil size and brightness levels on the monocular accommodative response.
Author Affiliations & Notes
  • Najnin Sharmin
    University College Dublin, Ireland, Dublin, Ireland
  • Brian Vohnsen
    University College Dublin, Ireland, Dublin, Ireland
  • Footnotes
    Commercial Relationships   Najnin Sharmin, None; Brian Vohnsen, None
  • Footnotes
    Support  European Union's Horizon H2020 ITN MyFUN project, grant agreement no. 675137
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 1793. doi:
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      Najnin Sharmin, Brian Vohnsen; Impact of pupil size and brightness levels on the monocular accommodative response.. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1793.

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

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Abstract

Purpose : The aim of this study is to explore the possible impact of pupil size and brightness levels on the monocular accommodative response for emmetropes and myopes. The relationship between Zernike aberration coefficients up to 4th order in response to induced defocus by a tunable lens will be analyzed. Ultimately, this may explain how the eye can detect the sign of defocus.

Methods : A near-IR (850 nm) laser diode was used in combination with a CMOS Hartmann-Shack wavefront sensor (Thorlabs) to capture aberrations up to the 4th Zernike order at 20 Hz. A motorized iris placed in the conjugate pupil plane was used to restrict viewing to a 2.5, 3.5, and 4.5 mm pupil, respectively, and a tunable liquid crystal neutral density filter (Meadowlark) was used to adjust brightness of a green Maltese cross target displaced on a computer monitor at 1 m viewing distance. A current driven tunable lens (Optotune) in a conjugate pupil plane made a sequence of random changes in optical power every 10 s within the accommodative range of each subject. In total 8 subjects, age 24 – 50 years have been measured and their monocular accommodative responses have been recorded.

Results : In all cases, subjects were able to accommodate in the correct direction to compensate induced defocus. The temporal response of each subject varied with different defocus steps and with the pupil size corresponding to different depths of focus. For emmetropes, the corrected accommodation amplitude was almost 100% identical to the induced defocus for all pupil sizes. In turn, for myopes the 2.5 mm pupil size decreased the accommodation amplitude to approximately 70-80% and for 3.5 mm pupil size it decreased to 80-90 %. The reaction time for emmetropes was (150ms – 400ms) while for myopes the reaction time tended to be longer (300ms – 500ms). We discuss the findings in relation to the volumetric absorption model of the photoreceptors (Vohnsen, et al. J. Vision 2017) to explain the break of symmetry between positive and negative defocus.

Conclusions : The analysis shows that accommodation reaction time is comparatively fast (150ms – 500ms) and thus the eye is capable of accommodating in the correct direction. A smaller pupil size increases the depth of focus, and thus the accommodation amplitude become smaller (mostly noticeable for myopes). No significant difference was found in the accommodative response with and without controlling the brightness.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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