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Predicting Transepithelial Phototherapeutic Keratectomy Outcomes Using Fourier Domain Optical Coherence Tomography

Cleary, Catherine MD*,†; Li, Yan PhD*,†; Tang, Maolong PhD*,†; Samy El Gendy, Nehal M. MD*,†,‡; Huang, David MD, PhD*,†

doi: 10.1097/ICO.0000000000000050
Basic Investigation

Purpose: The aim of this study was to use Fourier domain optical coherence tomography to predict transepithelial phototherapeutic keratectomy outcomes.

Methods: This is a prospective case series. Subjects with anterior stromal corneal opacities underwent an excimer laser phototherapeutic keratectomy (PTK) combined with a photorefractive keratectomy using the VISX S4 excimer laser (AMO, Inc, Santa Ana, CA). Preoperative and postoperative Fourier domain optical coherence tomography images were used to develop a simulation algorithm to predict treatment outcomes. Main outcome measures included preoperative and postoperative uncorrected distance visual acuities and corrected distance visual acuity.

Results: Nine eyes of 8 patients were treated. The nominal ablation depth was 75 to 177 μm centrally and 62 to 185 μm peripherally. Measured PTK ablation depths were 20% higher centrally and 26% higher peripherally, compared with those for laser settings. Postoperatively, the mean uncorrected distance visual acuity was 20/41 (range, 20/25–20/80) compared with 20/103 (range, 20/60–20/400) preoperatively. The mean corrected distance visual acuity was 20/29 (range, 20/15–20/60) compared with 20/45 (range, 20/30–20/80) preoperatively. The MRSE was +1.38 ± 2.37 diopters (D) compared with −2.59 ± 2.83 D (mean ± SD). The mean astigmatism magnitude was 1.14 ± 0.83 D compared with 1.40 ± 1.18 D preoperatively. Postoperative MRSE correlated strongly with ablation settings, central and peripheral epithelial thickness (r = 0.99, P < 0.00001). Central islands remained difficult to predict and limited visual outcomes in some cases.

Conclusions: Optical coherence tomography measurements of opacity depth and 3-dimensional ablation simulation provide valuable guidance in PTK planning. Post-PTK refraction may be predicted with a regression formula that uses epithelial thickness measurements obtained by optical coherence tomography. The laser ablation rates described in this study apply only to the VISX laser.

*Center for Ophthalmic Optics and Lasers, Casey Eye Institute, Oregon Health and Science University, Portland, OR;

Department of Ophthalmology, Doheny Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA; and

Department of Ophthalmology, Kaser Al Aini School of Medicine, Cairo University, Cairo, Egypt.

Reprints: David Huang, Casey Eye Institute, Oregon Health and Science University, 3375 SW Terwilliger Blvd, Portland, OR 97239 (e-mail:

Supported by NIH grant R01EY018184, research grant from Optovue, Inc, grant from Research to Prevent Blindness, Charles C. Manger III, MD, Chair in Corneal Laser Surgery endowment. Dr C. Cleary is supported by a grant from the Irish College of Ophthalmologists.

D. Huang, Y. Li, and M. Tang have significant financial interests in Optovue, Inc (Fremont, CA), a company that may have a commercial interest in the results of this research and technology. These potential conflicts of interest have been reviewed and managed by the Oregon Health and Science University. The other authors have no conflicts of interest to disclose.

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Received February 26, 2013

Accepted November 08, 2013

© 2014 by Lippincott Williams & Wilkins.