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Published on: September 18, 2012
Comparison of dual rotating Scheimpflug-Placido, swept-source optical coherence tomography, and Placido-scanning-slit
Yong Woo Lee1, Chul Young Choi1, Geun Young Yoon1
1From Sungkyunkwan University School of Medicine (Lee, Choi), Kangbuk Samsung Medical Center, Department of Ophthalmology, Seoul, South Korea; the University of Rochester Medical Center School of Medicine (Yoon), Department of Ophthalmology, New York, New York, USA.
Purpose:
To compare measurements of corneal indices using dual rotating Scheimpflug-Placido, swept-source optical coherence tomography (OCT), and Placido-scanning-slit systems.
Setting:
Kangbuk Samsung Hospital, Seoul, South Korea.
Design:
Prospective evaluation of diagnostic tests.
Methods:
Corneal topography measurements were performed using dual rotating Scheimpflug-Placido (Galilei G2), swept-source OCT (Casia SS-1000), and Placido-scanning-slit (Orbscan IIz) systems. The intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to evaluate the agreement between measurements.
Results:
Fifty post-refractive surgery eyes and 50 normal eyes were evaluated. The agreement in anterior keratometry and pachymetry between the 3 devices was high in both groups (ICC > 0.9). In both groups, the ICC values for posterior keratometry and eccentricity were high between the dual rotating Scheimpflug-Placido and swept-source OCT systems (ICC > 0.9) but not between the Placido-scanning-slit system and the other 2 systems. The Placido-scanning-slit system yielded much steeper values for posterior keratometry in both groups (P < .05). The ICC values for posterior corneal elevation were lower than 0.9 between all 3 devices. The dual rotating Scheimpflug-Placido and swept-source OCT systems showed relatively higher ICC values than the Placido-scanning-slit system in both groups. Maximum posterior elevations were highest with the Placido-scanning-slit system followed by the swept-source OCT system and then the dual rotating Scheimpflug-Placido system.
Conclusions:
Anterior keratometry obtained using 3 devices showed high degrees of agreement. Posterior keratometry and eccentricity showed greater agreement between the dual rotating Scheimpflug-Placido and swept-source OCT systems than with the Placido-scanning-slit system. The dual rotating Scheimpflug-Placido and swept-source OCT systems were equivalent in detecting the shape of the cornea and could be considered interchangeable.
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