Comparison of central corneal thickness measurements by ultrasonic pachymetry, Orbscan II, and SP3000P in eyes with glaucoma or glaucoma suspect.

Background: Intraocular pressure (IOP) measurements are affected by the central cornea thickness (CCT). The conventional method for CCT measurement is ultrasonic pachymetry. However, noncontact procedures lower the risk of infection and corneal damage. In this study, we compared the CCT measured by Orbscan II, SP3000P, and ultrasonic pachymetry in patients with glaucoma or glaucoma suspect.

Methods: The CCT of 208 eyes (46 eyes with glaucoma suspect, 42 with primary angle-closure glaucoma, and 120 with primary open-angle glaucoma) was measured using Orbscan II, SP3000P, and ultrasonic pachymetry. We compared the linear correlation of the CCT between each mode.

Results: The mean CCT measured by Orbscan II (563.63 ± 35.867 µm) was larger than with the other two devices. There were significant linear correlations between measurements with ultrasonic pachymetry and Orbscan II (Pearson correlation coefficient (r) = 0.793, p < 0.001), ultrasonic pachymetry and SP3000P (r = 0.890, p < 0.001), and Orbscan II and SP3000P (r = 0.803, p < 0.001). We divided the participants into 3 groups on the basis of the CCT measured with ultrasonic pachymetry: ≤ 500 µm, > 500 µm to ≤ 578 µm, and > 578 µm. There was no significant linear correlation between ultrasonic pachymetry and Orbscan II in the thin group. But, in the intermediate and thick CCT groups, there were significant linear correlations between each of the three devices.

Conclusion: We showed good linear correlations of CCT measurements between each of 3 devices, especially in the intermediate and thickest CCTs. These results will be helpful in predicting the relationship between IOP and CCT for the diagnosis and screening of glaucoma; even we used optic systems.