Agreement between Placido Disc, Scheimpflug, and Optical Coherence Tomography-Based Measurements of Corneal Topography in Healthy Myopic Individuals.

Purpose: To evaluate the agreement between topographical and tomographic measurements of the cornea with three methods of Placido-disc, Scheimpflug, and optical coherence tomography in normal eyes with myopic refractive error candidate for keratorefractive surgery.

Methods: Subjects within the age range of 18-55 years old candidates for keratorefractive surgery with no history of systemic disorder, eye diseases except refractive errors, and ocular surgery were enrolled in the study. The intraclass correlation coefficient and Bland-Altman diagrams evaluated the agreement between different devices.

Results: In this study, 97 subjects, including 35 men and 62 women, participated. There was a statistically significant agreement between the three corneal imaging devices' keratometry measures. Bland-Altman plots show a mean difference of 0.5 diopter (D) for mean anterior keratometry, and 95% limits of agreement reached the value ± 1.00 D for mean anterior astigmatism. Evaluation of the elevation maps showed that the central and maximum elevation of the cornea's anterior and posterior surfaces with Pentacam and Optopol have poor agreement.

Conclusion: Despite an excellent statistical agreement, the differences in the anterior keratometry values may not be clinically acceptable.