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The Effects of Severe Myopia on the Properties of Sampling Units in Peripheral Retina

Nagra, Manbir, PhD1; Gilmartin, Bernard, PhD, DSc2; Logan, Nicola, S., PhD2; Anderson, Stephen, J., PhD2*

doi: 10.1097/OPX.0000000000001199

SIGNIFICANCE Poor peripheral visual acuity in myopia may reflect, in part, photoreceptor misalignment with the exit pupil of the eye. We speculate that if such misalignment causes sufficient visual deprivation and/or disrupts retinal feedback processes, it may influence eye growth itself.

PURPOSE It is known that myopic eyes have a reduced peripheral resolution acuity relative to emmetropic eyes, though it remains unclear how mechanical stretching of the retina in myopia impacts on peripheral visual performance. Our aim was to determine how retinal stretching affects the properties of sampling units in peripheral vision.

METHODS Three-dimensional magnetic resonance imaging provided a depiction in vivo of ocular shape, allowing the inter-eye ratio of retinal image surface areas and the relative alignment of surfaces to be determined in our observer, who was unique in having severe myopia in the right eye (~21 D) but only modest myopia in the left (~3 D). Visual performance was assessed for the detection and direction discrimination of drifting sinusoids positioned 40° in the temporal retina. Applying the sampling theorem to our measures, we estimated the density and cut-off frequency of the underlying sampling units.

RESULTS The retinal image surface area of the right eye was 40% larger than that of the left and was rotated 8.9° anticlockwise relative to the left eye’s image surface. In agreement with a linear stretch model of myopia, the sampling density of the right eye was reduced by approximately the same ratio as that predicted from the inter-eye MRI data, namely, 1.18. However, the cut-off frequency (cycles/mm) of the right eye was approximately half that of the left, a reduction that cannot be explained solely by a linear areal expansion of retinal sampling units.

CONCLUSIONS Poor peripheral acuity in severe myopia may be caused, at least in part, by receptoral misalignment with the exit pupil.

1Centre for Applied Vision Research, City, University of London, London, United Kingdom

2School of Life and Health Sciences, Aston University, Birmingham, United Kingdom *

Submitted: September 6, 2017

Accepted: January 1, 2018

Funding/Support: The College of Optometrists and the Lord Dowding Fund for Humane Research.

Conflict of Interest Disclosure: None of the authors have reported a conflict of interest.

Author Contributions and Acknowledgments: Conceptualization: MN, BG, NL, SJA; Data Curation: MN, SJA; Formal Analysis: MN, BG, NL, SJA; Funding Acquisition: MN; Investigation: MN, SJA; Project Administration; MN, BG, SJA; Writing – Review & Editing: MN, BG, NL, SJA; Supervision: BG, SJA; Resources: NL, SJA; Methodology: SJA; Software: SJA; Writing – Original Draft: SJA.

The authors thank Mark Georgeson and Tim Meese for useful discussions, and our observer for his dedicated support with this research.

© 2018 American Academy of Optometry