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Variability of CLMI-X parameters, zonal Kmax, and single-point Kmax in keratoconus progression

Eye volume 37, pages 3197–3202 (2023)Cite this article

Subjects

Abstract

Objectives

To compare the repeatability of Cone Location and Magnitude Index expanded (CLMI.X) parameters of 2 mm diameter zone of greatest corneal curvature (Cspot-Axi) and 1 mm diameter zone of thinnest pachmymetry (Spot-Pach) with the maximum single point keratometry (Kmax), 3 mm Zonal Kmax (Z-Kmax3), and thinnest single point pachymetry (TP) in keratoconus (KC).

Methods

In this Comparative repeatability study, data from 36 eyes of 36 normal individuals and 72 eyes of 72 KC patients (28 eyes with ≤50.0D and 44 eyes with >50.0D Z-Kmax3) were analyzed. For each enrolled eye, imaging was done 6 times (3 consecutive acquisitions with a half hour break). For each parameter, the within-subject standard deviation (Sw) was calculated from the data of the six exams.

Results

In the normal group, Cspot-Axi-Sw was different from Kmax-Sw (p = 0.0004). Also, Z-Kmax3-Sw was different from Kmax-Sw (p = 0.0297). The difference between Cspot-Axi-Sw and Z-Kmax3-Sw was statistically significant (p = 0.0482). In the KC group, Sw were significantly different between Cspot-Axi and Kmax (p < 0.0001), and between Z-Kmax3 and Kmax (p < 0.0001). In the Z-Kmax3 ≤ 50.0D subgroup, Sw were different between Cspot-Axi and Kmax (p = 0.0002). In the Z-Kmax3 > 50.0D subgroup, Sw were different between Cspot-Axi and Kmax (p < 0.0001), and between Z-Kmax3 and Kmax (p < 0.0001). Sw differences between Spot-Pach and TP were not significant in any of the study groups (all P > 0.05).

Conclusions

In the diagnosis and follow up of KC, the zonal averages of Cspot-Axi and Z-Kmax3 are more reliable than the single point Kmax. The repeatability of Spot-Pach is similar to TP and both variables should suit the purpose equally.

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Fig. 1: Repeatabilty of different types of keratometric indices in normal (NL) eye, keratoconus (KC) eyes with Z-Kmax3 ≤ 50.0D and KC eyes with Z-Kmax3 > 50.0D.
Fig. 2: Repeatabilty of pachymetric indices in normal (NL) eye, keratoconus (KC) eyes with Z-Kmax3 ≤ 50.0 D and KC eyes with Z-Kmax3 > 50.0 D.

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Data availability

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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Authors and Affiliations

  1. Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran

    Hassan Hashemi & Soheila Asgari

  2. Department of Ophthalmology & Visual Sciences, The Ohio State University, Wexner Medical Center, Columbus, OH, USA

    Ashraf M. Mahmoud

  3. School of Computer, Mathematical, and Natural Sciences, Morgan State University, Baltimore, MD, USA

    Shiva Mehravaran

  4. Department of Ophthalmology & Visual Sciences, Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA

    Cynthia J. Roberts

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  1. Hassan Hashemi
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  2. Soheila Asgari
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  3. Ashraf M. Mahmoud
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  4. Shiva Mehravaran
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  5. Cynthia J. Roberts
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Contributions

Concept and design (HH, CJR), acquisition of data (HH, SA), statistical analysis (AMM), interpretation of result (HH, CJR, SM, and SA), drafting the manuscript (SA, CJR, and SM), critical revision and final approve (all authors).

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Correspondence to Hassan Hashemi.

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Competing interests

CJR is consultant for Oculus Optikgeräte GmbH and Ziemer Ophthalmic Systems AG, Germany. None of the remaining authors have any financial disclosures.

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Hashemi, H., Asgari, S., Mahmoud, A.M. et al. Variability of CLMI-X parameters, zonal Kmax, and single-point Kmax in keratoconus progression. Eye 37, 3197–3202 (2023). https://doi.org/10.1038/s41433-023-02476-1

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