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Distinguishing between contact lens warpage and ectasia: Usefulness of optical coherence tomography epithelial
Julie M Schallhorn1, Maolong Tang1, Yan Li1
1From the Department of Ophthalmology (Schallhorn) and the Francis I. Proctor Foundation (Schallhorn), University of San Francisco, San Francisco, California, and the Center for Ophthalmic Optics and Lasers (Tang, Li, Louie, Chamberlain, Huang), Casey Eye Institute, and Department of Ophthalmology, Oregon Health & Science University, Portland, Oregon, USA.
Purpose:
To distinguish between corneal ectasia and contact lens-related warpage by characteristic patterns on corneal topography and optical coherence tomography (OCT) epithelial thickness maps.
Setting:
Casey Eye Institute, Portland, Oregon, USA.
Design:
Prospective and retrospective case series.
Methods:
Axial and mean power maps were obtained on corneal topography systems. Epithelial thickness maps were generated using RTVue OCT. A sector divider was applied to all maps. The locations of the minimum epithelial thickness, maximum epithelial thickness, maximum axial power, and maximum mean power were determined based on sector averages. Agreement was defined as the extremums occurring in the same or adjacent sectors.
Results:
Twenty-one eyes with keratoconus, 6 eyes with forme fruste keratoconus (better eye of asymmetric keratoconus), and 15 eyes with contact lens-related warpage were identified. The keratoconus and forme fruste keratoconus eyes had coincident topographic steepening with epithelial thinning. The locations of minimum epithelial thickness and maximum axial power agreed in 90% of the keratoconic eyes, while the minimum epithelial thickness and maximum mean power agreed in 95% of them. Conversely, the warpage eyes had coincident topographic steepening with epithelial thickening and normal pachymetry maps. The locations of maximum epithelial thickness and maximum axial power agreed in 93% of the warpage eyes, while the maximum epithelial thickness and maximum mean power agreed in all warpage eyes.
Conclusion:
Results show that epithelial thickness maps and corneal topographic maps are powerful synergistic tools in evaluating eyes with abnormal topography and can help differentiate between keratoconus and nonectatic conditions.
