Comparison of Central Corneal Thickness Measurements between Noncontact Specular Microscopy and Ultrasound Pachymetry

PURPOSE: We compared and analyzed central corneal thickness (CCT) measurements according to the corneal thickness obtained with noncontact specular microscopy (NCSM) and ultrasound pachymetry (USP). METHODS: CCT was measured in the order of NCSM and USP by a single optometrist in 120 eyes of 120 healthy subjects. The measurements were compared between the devices and the measurement agreements and correlations between the devices were analyzed. To determine if the measurements differed depending on the thickness of the cornea, the patients were divided into three tertile groups from the thinnest patient by CCT measurement using USP, and then the differences in CCT measured by the two devices were analyzed. RESULTS: The CCT measurements using NCSM and USP were 548.25 ± 4.64 µm and 533.09 ± 35.96 µm, respectively. NCSM measurements were found to be thicker, showing statistically significant differences between the measurements (p < 0.001). The two examinations showed a high degree of correlation (r = 0.878; p < 0.01). In the three groups, the differences in CCT measurements between NCSM and USP were 12.93 ± 21.88 µm, 16.85 ± 15.89 µm, and 15.70 ± 20.46 µm, respectively, but the differences between the three groups were not statistically significant (p = 0.655). CONCLUSIONS: Our results show that although the differences in CCT measurements using NCSM and USP were consistent regardless of the corneal thickness, the CCT measurements by NCSM and USP were highly correlated.

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

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 0.900 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.

Assessment of the Reproducibility of Corneal Endothelial Cell Analysis with Non-Contact Specular Nicroscope

The noncontact autofocus specular microscope with incorporated semiautomated image analyzing program provide a rapid morphometric endothelial analysis. We evaluated the reproducibility of endothelial cell analysis with Konan noncon Robo-ca sp 8000 noncontact specular microscope. Specular microscopic examinations were performed three times each in twenty eyes by two examinations were performed three times one examiner. The difference of mean coefficient of variation of cell density evaluated by two examiners were not statistically significant(4.83% and 3.81, p=0.16). But, mean coefficient of variation of CV(coefficient variation of cell size, poluyimegathim) and hexagonality(pleomorphism) were statistically significantly different between two examiners(12.46%, 17.90%, p=0.04 and 12.30%, 8.40%, p=0.01, respectively). Repeatability evaluated by one examiner in two eyes showed small coefficient of variation of cell density(3.67% & 3.69%) and large coefficient of variation of CV(11.41% & 15.00%) and hexagonality(7.79% & 10.24%). In conclusion, our study has shown that Konan noncon Robo-ca sp 8000 noncontact specular microscope allows accurate estimation of endothelial cell density, But reproducibility of coefficient of variation of cell size and hexagonality analysis were lower than that of cell density analysis.