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

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

• Yang YS
• Koh JW

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 microm with NCSM, 535.24 +/- 30.54 microm with AS-OCT, and 546.38 +/- 30.70 microm 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.

Keyword

Anterior segment optical coherence tomography; Central corneal thickness; Noncontact specular microscopy; Ultrasound pachymetry

MeSH Terms

Microscopy*
Tomography, Optical Coherence
Ultrasonography

Figure

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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).

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  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.

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  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.

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  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.

Reference

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