June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
MIOCT-generated topography maps for astigmatism magnitude and axis calculation in corneal phantoms
Author Affiliations & Notes
  • Rishi Subrahmanyan
    Ophthalmology, Duke University, Durham, North Carolina, United States
  • Alice Liu
    Ophthalmology, Duke University, Durham, North Carolina, United States
  • William Raynor
    Biomedical Engineering, Duke University, Durham, North Carolina, United States
  • Jianwei David Li
    Biomedical Engineering, Duke University, Durham, North Carolina, United States
  • Ryan P McNabb
    Ophthalmology, Duke University, Durham, North Carolina, United States
  • Cynthia A Toth
    Ophthalmology, Duke University, Durham, North Carolina, United States
    Biomedical Engineering, Duke University, Durham, North Carolina, United States
  • Joseph Izatt
    Biomedical Engineering, Duke University, Durham, North Carolina, United States
    Ophthalmology, Duke University, Durham, North Carolina, United States
  • Anthony N Kuo
    Ophthalmology, Duke University, Durham, North Carolina, United States
    Biomedical Engineering, Duke University, Durham, North Carolina, United States
  • Footnotes
    Commercial Relationships   Rishi Subrahmanyan, None; Alice Liu, None; William Raynor, None; Jianwei Li, None; Ryan McNabb, Leica Microsystems (P); Cynthia Toth, Alcon Laboratories (P), EMMES (C), Hemasonics (P); Joseph Izatt, Carl Zeiss Meditec (P), Carl Zeiss Meditec (R), Leica Microsystems (R), Leica Microsystems (P), St. Jude Medical (P), St. Jude Medical (R); Anthony Kuo, Leica Microsystems (P)
  • Footnotes
    Support  NIH R01 EY024312; NIH U01-EY028079
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 2017. doi:
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      Rishi Subrahmanyan, Alice Liu, William Raynor, Jianwei David Li, Ryan P McNabb, Cynthia A Toth, Joseph Izatt, Anthony N Kuo; MIOCT-generated topography maps for astigmatism magnitude and axis calculation in corneal phantoms. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2017.

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

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Abstract

Purpose : Corneal surgeries such as penetrating keratoplasty (PKP) can result in significant postoperative refractive errors that are difficult to assess intraoperatively with the current standard of care. Microscope-Integrated OCT (MIOCT) has the potential to characterize corneal astigmatism intraoperatively to help improve post PKP refractive outcomes. Here, we report accurate detection of astigmatism magnitude and axis in software-generated and 3D-printed phantom corneas.

Methods : Software phantoms were designed using MATLAB to simulate the corneal surface with astigmatism from 0 – 6 diopters (D). Plastic, 3D-printed phantom corneas were designed with astigmatism from 0 – 6 D. Four phantoms in each group have astigmatism with steep axis at 180°, and two have astigmatism with steep axis at 0° to evaluate anisotropy in imaging direction. Printed phantoms were imaged with MIOCT. After manually segmenting the first frame as a pilot, each subsequent Bscan in the volume was automatically segmented to identify the epithelial surface. Segmentations were fit to a 6th order Zernike function and corrected for system-specific distortions. Astigmatism magnitudes and axes were calculated according to ANSI standards for all phantoms.

Results : Topography maps are shown for software (Figure 1) and 3D-printed (Figure 2) phantoms. For software phantoms, the mean absolute difference between calculated and reference astigmatism magnitude and axis was 0.012 D and 0 degrees, respectively, for phantoms with steep axis at 90° and was 0.016 D and 0 degrees, respectively, for phantoms with steep axis at 0°. For printed phantoms, the mean absolute difference between calculated and reference astigmatism magnitude and axis was 0.26 D and 2.7 degrees, respectively, for phantoms with steep axis at 90° and was 0.25 D and 8.1 degrees, respectively, for phantoms with steep axis at 0°.

Conclusions : We used the MIOCT-based corneal topography system on software and 3D-printed corneal phantoms to calculate astigmatism magnitude and axis. The system calculates astigmatism magnitude within approximately 0.25 D and detects axis within 10 degrees. This system has potential for intraoperative astigmatism assessment during procedures such as PKP.

This is a 2021 ARVO Annual Meeting abstract.

 

Software phantom topography maps. Steep (dashed) and flat (solid) axes are shown for each phantom.

Software phantom topography maps. Steep (dashed) and flat (solid) axes are shown for each phantom.

 

3D-printed phantom topography maps. Steep (dashed) and flat (solid) axes are shown for each phantom.

3D-printed phantom topography maps. Steep (dashed) and flat (solid) axes are shown for each phantom.

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