Journal List > J Korean Ophthalmol Soc > v.55(1) > 1009945

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

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.

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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).
jkos-55-59f1.tif
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.
jkos-55-59f2.tif
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.
jkos-55-59f3.tif
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.
jkos-55-59f4.tif
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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