June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
Effect of axial and lateral fixational eye movements in corneal topography measurement with OCT
Author Affiliations & Notes
  • Alberto de Castro
    Instituto de Optica Daza de Valdes, Madrid, Comunidad de Madrid, Spain
  • Eduardo Martinez-Enriquez
    Instituto de Optica Daza de Valdes, Madrid, Comunidad de Madrid, Spain
  • Pilar Urizar
    Instituto de Optica Daza de Valdes, Madrid, Comunidad de Madrid, Spain
  • Andrea Curatolo
    Instituto de Optica Daza de Valdes, Madrid, Comunidad de Madrid, Spain
  • Susana Marcos
    Instituto de Optica Daza de Valdes, Madrid, Comunidad de Madrid, Spain
  • Footnotes
    Commercial Relationships   Alberto de Castro, None; Eduardo Martinez-Enriquez, None; Pilar Urizar, None; Andrea Curatolo, None; Susana Marcos, WO2012146811A1 (P)
  • Footnotes
    Support  H2020-MSCA-COFUND-2015-FP-713694; Spanish government grant FIS2017-84753-R; FJC2018-038736-I; H2020 IMCUSTOMEYE 779960
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 2029. doi:
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      Alberto de Castro, Eduardo Martinez-Enriquez, Pilar Urizar, Andrea Curatolo, Susana Marcos; Effect of axial and lateral fixational eye movements in corneal topography measurement with OCT. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2029.

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

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Abstract

Purpose : The topography of the cornea can be quantified three-dimensionally with Anterior Segment Optical Coherence Tomography (OCT) systems. However, the measurement is not instantaneous and during the scan, fixational eye movements may influence the results. We used simulations to model the influence of axial and lateral eye movements in the variability of repeated corneal topography measurements.

Methods : We used experimental data from two custom-built Fourier domain anterior segment OCT systems collected in 28 participants. The first system was a spectral OCT (OCT1), with a repetition rate of 25K A-scans/s and 10x10mm (300x50 A-scans) lateral range, and the second a swept source OCT (OCT2), 200K A-scans/s, scanned 15x15mm (300x150 A-scans). The measurement time was 0.6 and 0.41 s respectively. Simulations of the acquisition in both systems were performed assuming lateral and axial eye movements using the MATLAB Image System Engineering Toolbox for Biology (ISETBIO). On each OCT scanner position, eye shifts were applied in the x y and z directions and the sag calculated. To simulate higher eye movements a factor F of 1.5 was applied. The central 3 mm of the data were fitted by a sphere (radius R) and the residuals were fitted by Zernike polynomials (6th order coefficients, zC). The standard deviation (std) of the fittings to simulated data and experimental results were compared.

Results : The maximum shift from the fixation point simulated by the eye movement model was 40 µm. OCT1/OCT2 average std across subjects was 0.18/0.17 mm for R, 3.96/3.46 for the 3rd and 3.33/1.65 µm for the 4th order zC. Simulations std for F=1 and 1.5 was 0.15/0.07 and 0.18/0.13 mm for R, 2.35/1.15 and 2.99/1.84 for the 3rd and 1.47/1.16 and 2.19/1.76 µm for the 4th order zC, respectively. When only lateral movements were considered, the simulations predicted 50% lower std values.

Conclusions : The simulations of the raster scan acquisition of corneal topographies including fixational eye movements modeled with the ISETBIO Toolbox predict with high accuracy the experimental variability in the fitting parameters when axial movements are included. While the statistics of the axial eye movements may be different than those in the lateral direction, these simulations can serve to understand the sources of variability in topography measurements and to evaluate different scanning patterns.

This is a 2021 ARVO Annual Meeting abstract.

 

OCT1 experimental results and simulations

OCT1 experimental results and simulations

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