J Korean Ophthalmol Soc JKOS Journal of the Korean Ophthalmological Society 0378-6471 2092-9374 The Korean Ophthalmological Society 10.3341/jkos.2012.53.10.1432 Original Article Comparison of Anterior and Posterior Elevation, and Sagittal Curvature between Keratoconus and Normal Cornea Lee Jong Soo MD PhD 1 Lee Seung Wook MD 2 Lee Seung Min MD 1 Lee Mi Hyun MD 3 Department of Ophthalmology, Pusan National University School of Medicine, Busan, Korea. Department of Ophthalmology, Kosin University College of Medicine, Busan, Korea. Department of Ophthalmology, The Pusan Veterans Hospital, Busan, Korea. Address reprint requests to Jong Soo Lee, MD, PhD. Department of Ophthalmology, Pusan National University Hospital, #179 Gudeok-ro, Seo-gu, Busan 602-739, Korea. Tel: 82-51-240-7323, Fax: 82-51-242-7341, jongsool@pusan.ac.kr 10 2012 17 10 2012 53 10 1432 1437 06 04 2012 18 09 2012 Copyright © 2012 The Korean Ophthalmological Society 2012 Purpose

To compare changes of anterior and posterior corneal elevation, and sagittal curvature according to the severity of keratoconus and to compare differences between keratoconus and normal cornea.

 Methods

A total of 81 eyes diagnosed with keratoconus and 20 eyes of normal subjects were evaluated with a Pentacam Scheimpflug camera. The keratoconus eyes were divided into 3 groups according to mean keratometer (K): mild (K ≤ 47.0 diopters (D)), moderate (47.0 to 52.0 D), and severe (52.0 D≥). The following parameters were obtained to evaluate the correlation of keratoconus: corneal thickness, anterior and posterior corneal elevation, and sagittal curvature.

 Results

Out of 81 keratoconus eyes, 56 eyes were mild, 12 eyes were moderate, and 13 eyes were severe keratoconus. The mean central corneal keratometer, anterior and posterior corneal elevation, and sagittal curvature of the keratoconus eyes were 49.7 D, 22.07 µm, 38.16 µm, 52.76 D and the values increased statistically compared to the normal eyes. Furthermore, the values increased significantly with the severity of keratoconus. ROC curve analysis showed the estimated meaningful value for anterior and posterior corneal elevation and sagittal curvature of keratoconus for diagnosis; there were no diagnostic values for corneal thickness and refractive power.

 Conclusions

The index of 5.5 µm for mean anterior elevation, 12.5 µm for mean posterior elevation, and 44.5 µm for mean sagittal curvature using the Pentacam® are useful to diagnose keratoconus. Variation of anterior and posterior elevation, and sagittal curvature measured by Pentacam® are useful in understanding the process of keratoconus.

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Comparison of parameters of Pentacam® (OCULUS, Germany) in keratoconic and normal eyes.(A) Keratometry. (B) Corneal thickness. (C) Anterior and posterior elevation. (D) Sagittal curvature.

Receiver operating characteristic (ROC) graph showing the sensitivity and specificity of the various corneal measurements. The closer the line to the left-hand side of the graph, the higher the sensitivity and specificity for keratoconus.

Demographic features, visual acuity and refractive outcomes

BCVA = best corrected visual acuity.

Values are presented as mean ± SD or number

Comparison of parameters of Pentacam® (OCULUS, Germany) in keratoconic and normal eyes

Values are presented as mean ± SD.

The parameters including central corneal power, anterior and posterior elevation from BFS, corneal thickness and sagittal curvature.