Precision of corneal thickness measurements obtained using the scheimpflug-placido imaging and agreement with ultrasound pachymetry.

Jinhai Huang,Giacomo Savini,Chengfang Wang,Yuanguang Li,Rongrong Gao,Weicong Lu,Yune Zhao,Qinmei Wang

doi:10.1155/2015/328798

Jinhai Huang, Giacomo Savini + Show 6 more

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https://doi.org/10.1155/2015/328798

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Abstract

Purpose. To assess the reliability and comparability of measuring central corneal thickness (CCT) and thinnest corneal thickness (TCT) using a new Scheimpflug-Placido analyzer (TMS-5, Japan) and ultrasound (US) pachymetry. Methods. Seventy-six healthy subjects were prospectively measured 3 times by 1 operator using the TMS-5, 3 additional consecutive scans were performed by a second operator, and ultrasound (US) pachymetry measurements were taken. The test-retest repeatability (TRT), coefficient of variation (CoV), and intraclass correlation coefficient (ICC) were calculated to evaluate intraoperator repeatability and interoperator reproducibility. Agreement among the devices was assessed using Bland-Altman plots and 95% limits of agreement (LoA). Results. The intraoperators TRT and CoV were <19 μm and 2.0%, respectively. The interoperators TRT and CoV were <12 μm and 1.0%, respectively, and ICC was >0.90. The mean CCT and TCT measurements using the TMS-5 were 15.97 μm (95% LoA from −26.42 to −5.52 μm) and 20.32 μm (95% LoA from −30.67 to −9.97 μm) smaller, respectively, than those using US pachymetry. Conclusions. The TMS-5 shows good repeatability and reproducibility for measuring CCT and TCT in normal subjects but only moderate agreement with US pachymetry results. Caution is warranted before using these techniques interchangeably.

Highlights

Precise measurement of central corneal thickness (CCT) is important when planning excimer laser surgery and diagnosing glaucoma and other corneal diseases [1, 2]
An overestimation of CCT and the thinnest corneal thickness (TCT) before corneal refractive surgery could lead to corneal stroma overablation, especially in eyes with a high degree of myopia or borderline corneal thickness or that require enhancement surgeries, and can increase the risk of keratectasia [3]
CCT and TCT; it has moderate resolution and precision, depends on operator skills, and causes discomforting to the patient [16, 17]; noncontact devices represent a more desirable alternative and have been widely applied in both clinical practice and research settings, there remains an issue with their precision

Summary

Introduction

Precise measurement of central corneal thickness (CCT) is important when planning excimer laser surgery and diagnosing glaucoma and other corneal diseases [1, 2]. Several technologies for measuring corneal thickness are available, the most common of which, for many years, has been ultrasound (US) pachymetry, which is regarded as the gold standard because of its low cost, compact design, ease of use, and high repeatability; US pachymetry requires direct corneal contact, which causes an indentation of the cornea and could lead to false results [5]. Contact with a patient’s eyes could cause discomfort or even damage the corneal epithelium [8]. These limitations led to the development of different, more sophisticated, noncontact technologies, such as Scheimpflug imaging. Rotating Scheimpflug cameras include the Pentacam (Oculus, Wetzlar, Germany), Sirius

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