September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
To differentiating keratoconus and contact lens-related corneal warpage by combining pattern analysis of focal changes in anterior corneal topography, pachymetry, and epithelial thickness maps.
Author Affiliations & Notes
  • Maolong Tang
    Oregon Health and Science University, Portland, Oregon, United States
  • Yan Li
    Oregon Health and Science University, Portland, Oregon, United States
  • David Huang
    Oregon Health and Science University, Portland, Oregon, United States
  • Footnotes
    Commercial Relationships   Maolong Tang, Optovue Inc. (F), Optovue Inc. (P); Yan Li, Optovue Inc. (F), Optovue Inc. (P); David Huang, Carl Zeiss Meditec Inc. (P), Optovue Inc. (F), Optovue Inc. (I), Optovue Inc. (P)
  • Footnotes
    Support  This study was supported by NIH grants R01 EY018184, a grant from Optovue Inc. a NIH Core grant (P30 EY010572) and an unrestricted grant from Research to Prevent Blindness.
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 2903. doi:
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    • Get Citation

      Maolong Tang, Yan Li, David Huang; To differentiating keratoconus and contact lens-related corneal warpage by combining pattern analysis of focal changes in anterior corneal topography, pachymetry, and epithelial thickness maps.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2903.

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

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Abstract

Purpose : To differentiating keratoconus and contact lens-related corneal warpage by combining pattern analysis of focal changes in anterior corneal topography, pachymetry, and epithelial thickness maps.

Methods : All keratoconic eyes had abnormal topography and best-corrected visual acuity of 20/25 or worse. Contact lens warpage was defined as contact lens wearers with topographic inferior-superior asymmetry greater than 1.4 D or 5-mm zone irregularity index >1.5 D on slit-scanning topographer (Orbscan). Pachymetry and epithelial thickness maps were obtained from a commercial Fourier-domain OCT system (RTVue). Warpage Index was calculated by the cross-correlation of Pattern deviation (PD) maps of anterior topography and epithelial thickness. Positive correlation indicates warpage, and negative correlation indicates keratoconus. Anterior Ectasia Index was based on Gaussian fitting of PD maps of anterior corneal topography and pachymetry. Its magnitude represented the coincident focal topographic steepening and epithelial thinning. Epithelial Patterns Standard Deviation (PSD) was also computed.

Results : The study included 36 keratoconic eyes and 11 eyes with contact lens warpage. The Epithelial PSD was normal (0.021±0.0075; threshold=0.035) for all normal eyes, and abnormal for all keratoconic (0.083 ± 0.034) and warpage (0.055 ± 0.023) eyes. The average Anterior Ectasia Index was normal (threshold=6.7) for all normal (1.66 ± 0.74) and warpage (2.76 ± 1.45) eyes, and abnormal (17.5 ± 7.18) in all keratoconic eyes. The Warpage Index was positive in all warpage eyes (0.12 ± 0.089) and all except one normal eyes, (0.065 ± 0.050) and negative (-0.58 ± 0.52) for all except one keratoconus eyes. The one keratoconus eye with positive Warpage Index was a wearer of rigid gas-permeable contact lens.

Conclusions : The Epithelial PSD was able to perfectly distinguish normal eyes from those having either keratoconus or warpage, but do not distinguish the 2 pathologies. The novel Anterior Ectasia Index is abnormal in keratoconic eyes but not warpage eyes. The novel Warpage Index is positive for all warpage eyes and negative for all keratoconus eyes, except in some cases where both keratoconus and warpage co-exist. Together, the 3 OCT-based parameters are strong tripartite discriminators of normal, keratoconus, and warpage.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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