Orbscan and ultrasound pachymetry in patients with ocular hypertension and normal tension glaucoma

Abstract

Aim: To compare central corneal thickness measurements using an ultrasound pachymeter and an Orbscan.

Patients and methods: Normal subjects and patients with ocular hypertension, and with normal tension glaucoma were recruited at the Tung Wah Eastern Hospital Eye Centre, Hong Kong. Central corneal thickness was measured using the ultrasound pachymeter and the Orbscan for one selected eye per patient and the results compared between groups.

Results: Mean central corneal thickness for normal subjects, patients with ocular hypertension, and patients with normal tension glaucoma were 550.1 ± 21.4 mm, 598.5 ± 27.2 mm, and 525.8 ± 24.9 mm, respectively, when measured by ultrasound. Using the Orbscan, mean central corneal thickness was 561.9 ± 26.0 mm for normal subjects, 590.2 ± 26.4 mm for those with ocular hypertension, and 528.8 ± 28.7 mm for those with normal tension glaucoma. Pearson’s correlation coefficients between ultrasound and Orbscan measurements were 0.82 (p < 0.001), 0.87 (p < 0.001), and 0.83 (p < 0.001) for normal subjects, those with ocular hypertension, and normal tension glaucoma, respectively.

Conclusions: Central corneal thickness is increased in ocular hypertension but decreased in normal tension glau- coma. Ultrasound and Orbscan measurements of central corneal thickness were highly correlated in this study.