June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Highly Asymmetric Corneal Optics Can Induce Eccentric Fixation
Author Affiliations & Notes
  • Seungpil Bang
    Biomedical Engineering, University of Rochester Hajim School of Engineering and Applied Sciences, Rochester, New York, United States
    University of Houston College of Optometry, Houston, Texas, United States
  • Dibyendu Pusti
    University of Houston College of Optometry, Houston, Texas, United States
  • Geunyoung Yoon
    University of Houston College of Optometry, Houston, Texas, United States
  • Footnotes
    Commercial Relationships   Seungpil Bang None; Dibyendu Pusti None; Geunyoung Yoon None
  • Footnotes
    Support  NIH Grant EY014999; Asan Foundation Scholarship; GC Pharma Scholarship
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 2887. doi:
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    • Get Citation

      Seungpil Bang, Dibyendu Pusti, Geunyoung Yoon; Highly Asymmetric Corneal Optics Can Induce Eccentric Fixation. Invest. Ophthalmol. Vis. Sci. 2023;64(8):2887.

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

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Abstract

Purpose : It has long been known that eccentric fixation is an eye’s adaptive strategy to utilize a healthy part of the retina for fixation in patients with macular diseases and central scotoma. We recently hypothesized that a highly asymmetric cornea found in keratoconus patients could induce a significant shift in the retinal fixation area from the fovea. This study aimed to test the hypothesis by comparing retinal fixation in keratoconic and normal eyes.

Methods : Both keratoconic (age: 27 to 56 years, n = 6) and normal (age: 28 to 41 years, n = 7) participants were enrolled in the study. Spectral-domain optical coherence tomography (OCT, Heidelberg Engineering) was used to assess the retinal fixation area, and the shift was measured as a visual angle deviated from the fovea. The visual angle was estimated from the retinal fixation point and the axial length measured with Lenstar (LS 900, Haag-Streit). The magnitude of the shifts was correlated with the severity of keratoconus and the asymmetric aberrations, assessed by Pentacam HR (Oculus).

Results : The eccentric fixation was shifted significantly in the vertical direction (mean: 0.78° ± 0.45° [0.36° ~ 1.77°]) compared to the horizontal direction (mean: 0.28° ± 0.24° [0.02° ~ 0.64°], P = 0.004) in the keratoconic eyes. In the normal eyes, the horizontal fixation shift (mean: 0.09° ± 0.07° [0.01° ~ 0.21°]) was larger compared to the vertical direction (mean: 0.031° ± 0.027° [0.001° ~ 0.085°], P = 0.008). The average total fixation shift between the two groups was significantly different: 0.86° ± 0.43° for the keratoconic eyes and 0.10° ± 0.06° for the normal eyes (P < 0.001). The fixation shift in the keratoconic eyes was correlated positively with the severity (R = 0.52; P = 0.002) and the vertical coma (R = 0.68; P = 0.016).

Conclusions : Significantly large eccentric fixation toward the vertical visual field was found especially in keratoconic eyes compared to normal eyes. Given that the keratoconic corneas are characterized by large vertical coma, we speculated that the highly asymmetric corneal optics could cause the retinal fixation area to shift from the fovea and this shift might have occurred with the disease progression as a mechanism that optimizes visual quality despite the slight loss of resolution.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

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