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Cornea:
doi: 10.1097/ICO.0000000000000050
Basic Investigation

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*,†

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Abstract

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.

Copyright © 2014 by Lippincott Williams & Wilkins

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