Optical Coherence Tomography Accurately Measures Corneal Power Change from Laser Refractive Surgery

• Published in: Ophthalmology (Rochester, Minn.) Vol. 122; no. 4; pp. 677 - 686
• Main Authors: McNabb, Ryan P., PhD, Farsiu, Sina, PhD, Stinnett, Sandra S., DPH, Izatt, Joseph A., PhD, Kuo, Anthony N., MD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.2015
• Subjects: Adult; Astigmatism - physiopathology; Biometry; Cornea - physiopathology; Corneal Topography; Female; Humans; Keratomileusis, Laser In Situ - methods; Lasers, Excimer - therapeutic use; Male; Middle Aged; Myopia - physiopathology; Myopia - surgery; Ophthalmology; Refraction, Ocular - physiology; Tomography, Optical Coherence; Young Adult; OCT; D; distributed scanning optical coherence tomography; manifest refraction; optical coherence tomography; CI; ICC; SD; MRx; SD-OCT; DSOCT; CCT; spectral domain optical coherence tomography; diopter; intraclass correlation coefficient; confidence interval; central corneal thickness; standard deviation
• ISSN: 0161-6420; 1549-4713
• DOI: 10.1016/j.ophtha.2014.10.003

Purpose To determine the ability of motion-corrected optical coherence tomography (OCT) to measure the corneal refractive power change due to LASIK. Design Evaluation of a diagnostic test or technology in a cohort. Subjects A total of 70 eyes from 37 subjects undergoing LASIK were measured preoperatively. A total of 39 eyes from 22 subjects were measured postoperatively and completed the study. Methods Consecutive patients undergoing LASIK at the Duke Eye Center who consented to participate were imaged with Placido-ring topography, Scheimpflug photography, and OCT on the day of their surgery. Patients were then reimaged with the same imaging systems at the postoperative month 3 visit. Change in preoperative to postoperative corneal refractive power as measured by each of the imaging modalities was compared with the preoperative to postoperative change in manifest refraction (MRx) using the t test with generalized estimating equations. Main Outcome Measures Corneal refractive power change due to LASIK as measured by Placido-ring topography, Scheimpflug photography, and OCT compared with the MRx change vertexed to the corneal plane. The change in MRx should correspond to the change in the corneal refractive power from LASIK and was considered the reference measurement. Results In 22 individuals (39 eyes) returning after LASIK, we found no significant difference between the clinically measured pre- to post-LASIK change in MRx and both Scheimpflug photography ( P  = 0.714) and OCT ( P  = 0.216). In contrast, keratometry values from Placido-ring topography were found to be significantly different from the measured refractive change ( P < 0.001). In addition, of the 3 imaging modalities, OCT recorded the smallest mean absolute difference from the reference measurement with the least amount of variability. Conclusions Motion-corrected OCT more accurately measures the change in corneal refractive power due to laser refractive surgery than other currently available clinical devices. By offering accurate corneal refractive power measurements in normal and surgically modified subjects, OCT offers a compelling alternative to current clinical devices for determining corneal refractive power.