Utility of the Noncontact Specular Microscopy for Measurements of Central Corneal Thickness

Young Seong Yang; Jae Woong Koh

doi:10.3341/jkos.2014.55.1.59

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Yang and Koh: Utility of the Noncontact Specular Microscopy for Measurements of Central Corneal Thickness

Original Article

J Korean Ophthalmol Soc 2014;55(1):59-65.

Published online: 7 September 2014

DOI: https://doi.org/10.3341/jkos.2014.55.1.59

Utility of the Noncontact Specular Microscopy for Measurements of Central Corneal Thickness

Young Seong Yang, MD, Jae Woong Koh, MD, PhD

Department of Ophthalmology, Chosun University College of Medicine, Gwangju, Korea

Address reprint requests to Jae Woong Koh, MD, PhD Department of Ophthalmology, Chosun University Hospital, #365 Pilmun-daero, Dong-gu, Gwangju 501-717, Korea, Tel: 82-62-220-3190, Fax: 82-62-225-9839, E-mail: ophkoh@hanmail.net

Received 29 March 201320 August 2013 Accepted 20 November 2013

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To evaluate the efficacy of noncontact specular microscopy (NCSM) by comparing the measurement of central corneal thickness (CCT) to the measurement with anterior segment optical coherence tomography (AS-OCT) and ultrasound pachymetry (USP).

Methods

One examiner measured the CCT of 50 eyes of 50 healthy young subjects using NCSM, AS-OCT, and USP. The mean values and correlations were analyzed.

Results

The mean CCT value was 546.92 ± 32.06 μm with NCSM, 535.24 ± 30.54 μm with AS-OCT, and 546.38 ± 30.70 μm with USP. The CCT measurements with NCSM and USP were significantly thicker than with AS-OCT (p < 0.001, p < 0.001, respectively). There were no significant differences between the measurements obtained with NCSM and USP (p = 0.505). The 3 instruments were significantly correlated (r > 0.900 in all groups, p < 0.001 in all groups).

Conclusions

CCT measurements of healthy eyes using NCSM are more correlated with USP than AS-OCT. The CCT measurement using NCSM is a better alternative for USP than AS-OCT.

Keywords: Anterior segment optical coherence tomography, Central corneal thickness, Noncontact specular microscopy, Ultrasound pachymetry

References

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Figure 1.

Mean value, 95% confidence interval (CI) and range of central corneal thickness (CCT) measured by noncontact specular microscopy (NCSM), anterior segment optical coherence tomography (AS-OCT) and ultrasound pachymetry (USP).

Figure 2.

The correlation plot of the central corneal thickness (CCT) measured by noncontact specular microscopy (NCSM), anterior segment optical coherence tomography (AS-OCT) and ultrasound pachymetry (USP). (A) Correlation between NCSM and USP (r = 0.984, p < 0.001); The best-fit line (y = 30.8 +0.94x) is designated by solid line, and the equivalent line (y=x) by dashed line. (B) Correlation between NCSM and AS-OCT (r = 0.965, p < 0.001); The best-fit line (y = 32.7 +0.92x) is designated by solid line, and the equivalent line (y=x) by dashed line. (C) Correlation between AS-OCT and USP (r = 0.971, p < 0.001); The best-fit line (y = 24.1+ 0.98x) is designated by solid line, and the equivalent line (y = x) by dashed line.

Figure 3.

Bland-Altman plots between the 2 instruments. The middle solid line represents the mean difference in central corneal thickness (CCT) values and the upper and lower dashed lines represent the crude 95% limits of agreement (LoA). (A) Noncontact specular microscopy (NCSM) and ultrasound pachymetry (USP). (B) NCSM and anterior segment optical coherence tomography (AS-OCT). (C) AS-OCT and USP.

Figure 4.

Anterior segment photo in a patient with keratouvei-tis, shows corneal edema with peripheral neovascularization. Central corneal thickness (CCT) measured by ultrasound pachymetry (USP) was 780 μm, measured by anterior segment optical coherence tomography (AS-OCT) was 757 μm, and measured by noncontact specular microscopy (NCSM) was 485 μm.

Table 1.

Central corneal thickness (CCT) measured by noncontact specular microscope (NCSM), anterior segment optical coherence tomography (AS-OCT), and ultrasound pachymetry (USP)

	NCSM	AS-OCT	USP	p-value^*
CCT (μm)	546.92 ± 3.06	535.24 ± 30.54	546.38 ± 30.70	0.007^†

Values are presented as mean ± SD.

^* Repeated-measures ANOVA

^† CCT measured with NCSM and USP was significantly thicker than with AS-OCT but there was no significant difference between NCSM and USP.

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