June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Real-time mimicking of accommodative microfluctuations by a tunable lens and monocular sensing of the sign of defocus
Author Affiliations & Notes
  • Najnin Sharmin
    School of Physics, University College Dublin, Dublin, Leinster, Ireland
  • Brian Vohnsen
    School of Physics, University College Dublin, Dublin, Leinster, Ireland
  • Footnotes
    Commercial Relationships   Najnin Sharmin None; Brian Vohnsen None
  • Footnotes
    Support  H2020 ITN MyFUN grant agreement No. 675137 and Enterprise Ireland IP20200951
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 3059 – F0531. doi:
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      Najnin Sharmin, Brian Vohnsen; Real-time mimicking of accommodative microfluctuations by a tunable lens and monocular sensing of the sign of defocus. Invest. Ophthalmol. Vis. Sci. 2022;63(7):3059 – F0531.

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

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Abstract

Purpose : Accommodative microfluctuations may potentially play a role in the detection of the sign of defocus. The aim of this study was to examine the temporal dynamics of accommodation with and without microfluctuations in the young adult eye. This can provide insight into whether defocus is sensed by the eye and its possible relation to emmetropization.

Methods : Real-time accommodation, with and without microfluctuations (MFs), was analyzed in a monocular vision system with a Hartmann-Shack wavefront sensor (HS-WFS) capturing up to the 4th radial Zernike order at 25 Hz, used along a tunable lens (TL), and a near-IR beacon at 850 nm. Subjects viewed with the right eye a green Maltese cross target (0.86°) on a dark computer screen placed at 1-m distance with a 3 mm pupil. The power of the TL was coded both to trigger an accommodative response and, when desired, to replicate and cancel MFs during the accommodative process using the defocus signal from the HS-WFS. Three subjects (2 emmetropes, 1 myope) were analyzed. In the first set of measurements, it generated constant defocus step changes (from 0 D to the comfortable accommodative range of the subject) at random time intervals (within 5 to 9 s). In the second set of measurements, the TL made the same random-time defocus step changes while mimicking, with opposite sign, detected MFs.

Results : The accommodation followed defocus steps accurately both with and without MFs for all of the subjects. Some accommodation overshooting was noticed when the MFs were mimicked by the TL. The reaction time was found to be in the range of 300 – 750 ms and the response time was found in the range of 250 – 1500 ms. It was noticed that almost in 50% of the cases, the reaction and response time was longer when MFs were compensated by the TL, while for the remaining cases both times were either similar or even faster with MFs compensation.

Conclusions : The findings show that in the absence of MFs accommodation is still in the correct direction. The accommodative response time increased with an increased magnitude of step changes and with the increased measurement time but was only weakly affected by the removal of the MFs cue. Thus, MFs may predominantly aid to maintain an average accommodation level rather than to provide the required direction of accommodation.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

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