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Assessment of corneal epithelial and stromal topographic and optical characteristics by use of intraoperative swept-source OCT-based topo/tomography performed after epithelial removal

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First Author: A.Stojanovic NORWAY

Co Author(s):    A. Stojanovic                    

Abstract Details

Purpose:

To quantify the epithelial contribution to the corneal topography and optics and asses the viability of intraoperative stromal topography measurements by swept-source optical coherent tomography (OCT)-based topo/tomography.

Setting:

Prospective, consecutive case series from the eye department of the University Hospital in Tromsø, Norway.

Methods:

Twenty-two eyes of 19 patients referred to phototherapeutic keratotomy (PTK) for treatment of recurrent corneal erosion were enrolled to the study. Swept-source OCT-based corneal topo/tomography was registered right-before and right-after mechanical epithelial removal within the PTK procedure, and each measurement was repeated three times consecutively. Epithelial thickness profile was obtained in advance of the surgery by use of spectral domain OCT. Topographic and optical characteristics including curvature of the best fitting sphere, astigmatism, asphericity and HOAs of epithelial and stromal surfaces were compared, and their differences were correlated with the measurements derived from the epithelial thickness profile.

Results:

Comparing to stromal surface, epithelial surface was flatter by 1.28D and 0.43D for φ3.5mm and φ6mm zone, respectively, and had lower with-the-rule astigmatism by 0.41D, as well as less prolate asphericity and HOAs. These differences correlated well with the parameters derived from the epithelial thickness profile. Amount of corneal edema induced by deepithelialization did not significantly influence any of the measured parameters on the anterior cornea. All measurements with swept-source OCT-based topography showed excellent repeatability.

Conclusions:

A significant epithelial contribution to anterior corneal topography and optics was confirmed by comparing corneal topography before and after deepithelialization. Immediate measurement of stromal topography right after mechanical epithelial removal with use of swept-source OCT-based topography may be a viable method in therapeutic refractive surgery, where stromal topography-guided ablation is needed.

Financial Disclosure:

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