June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Impact of Long-Term Neural Adaptation to Ocular Aberrations on Phase Perception
Author Affiliations & Notes
  • John Thomas Pirog
    Institute of Optics, University of Rochester, San Antonio, Texas, United States
    Flaum Eye Institute, University of Rochester, Rochester, New York, United States
  • Antoine Barbot
    Flaum Eye Institute, University of Rochester, Rochester, New York, United States
  • Geunyoung Yoon
    Flaum Eye Institute, University of Rochester, Rochester, New York, United States
    Institute of Optics, University of Rochester, San Antonio, Texas, United States
  • Footnotes
    Commercial Relationships   John Pirog, None; Antoine Barbot, None; Geunyoung Yoon, Bausch and Lomb (F), Coopervision (F), Johnson and Johnson (F), Ovitz (C), Ovitz (F)
  • Footnotes
    Support  NIH/NEI EY014999 and Research to Prevent Blindness
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 2495. doi:
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      John Thomas Pirog, Antoine Barbot, Geunyoung Yoon; Impact of Long-Term Neural Adaptation to Ocular Aberrations on Phase Perception. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2495.

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

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Abstract

Purpose : Optical aberrations degrade the amplitude and phase relationships among spatial frequencies (SFs) in the retinal image. Furthermore, long-term exposure to optical aberrations progressively alters visual processing through neural adaptation mechanisms [Sabesan & Yoon, 2009; Barbot & al., 2016]. The goal of this study is to test the hypothesis that neural compensation for phase shifts between SFs is one of the mechanisms underlying this adaptive process.

Methods : Three subjects with Keratoconus (KC)–a corneal disease that progressively degrades optical quality in normally-developed visual systems–were tested under full adaptive optics (AO) correction. Subjects reported the appearance of suprathreshold horizontal compound grating stimuli consisting of a fundamental frequency F (6 c/deg) and a secondary frequency 2F (12 c/deg). We manipulated the relative phase shift between the F and 2F components and asked subjects to judge whether the 2F component was phase shifted upwards or downwards relative to the F. Normal subjects (n=2) were tested under full AO correction and under AO-induced vertical coma (±0.33 and ±0.66 µm). Data were fitted with a Weibull psychometric function to estimate the point-of-subjective equality (PSE)–the phase shift at which subjects perceived the 2F to be upwards or downwards 50% of the time.

Results : Under AO-correction, normal eyes accurately perceived the phase shift in the 2F frequency, with a PSE centered on 0° shift (-0.58±2.4°). Under induced vertical coma, normal eyes’ PSEs shifted either leftward or rightward with negative and positive vertical coma (±0.33 µm: ±11±4.5°; ±0.66 µm: ±24.6±2.4°), respectively. This shift was proportional to the magnitudes of induced coma suggesting that normal eyes are sensitive to alterations in phase relationships. Under full AO-correction, however, KC patients showed substantial alterations in perceived phase relationships, ranging from -16.94° to +26.25°, which may be explained by the habitual large-magnitude ocular aberrations.

Conclusions : We developed a method to accurately measure and assess sensitivity to phase shifts between SFs under various optical conditions. Our preliminary data additionally shows that under aberration-free conditions, KC eyes show measurable alterations in phase relationships between SFs. Altogether, our findings seem to suggest a neural compensatory mechanism for phase through long-term exposure to ocular aberrations.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

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