Predicting transepithelial phototherapeutic keratectomy outcomes using Fourier domain optical coherence tomography.
OBJECTIVE
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.
Catherine
C
Cleary
Yan
Y
Li
Maolong
M
Tang
Nehal M
NM
Samy El Gendy
David
D
Huang
D000328:Adult; D000368:Aged; D000465:Algorithms; D003315:Cornea / Q000473:pathology / Q000601:surgery; D003317:Corneal Dystrophies, Hereditary / Q000503:physiopathology / Q000601:surgery*; D003318:Corneal Opacity / Q000503:physiopathology / Q000601:surgery*; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000473:pathology / Q000601:surgery*; D019573:Epithelium, Corneal; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D018903:Photorefractive Keratectomy / Q000379:methods*; D011446:Prospective Studies; D041623:Tomography, Optical Coherence; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult