PURPOSE: To compare central corneal thickness measurements made using two different
methods, optical coherence tomography (OCT) and ultrasound pachymetry, applied both
in normal eyes and in eyes on which photorefractive keratectomy (PRK) had been performed.
A second objective was to assess the intrasession variability of OCT measurements.
METHODS: In this prospective study, central corneal thickness was measured in 20 normal
subjects (normal group) and in 20 PRK patients using the StratusOCT instrument model
3000 (Carl Zeiss Meditec), and also with an ultrasound pachymeter. Five OCT measurements
were performed using the Fast Macular Thickness protocol. Corneal thickness data were
obtained with the Scan Profile analysis protocol. The OCT measurement results were
compared with the mean value of three ultrasound pachymetry measurements for the same
eye. RESULTS: The pachymetry-OCT correlation coefficients were 0.96 and 0.97 in the
normal and PRK groups, respectively (p=0.14). Neither linear regression nor Bland-Altmann
analysis revealed any significant systematic measurement error. Intrasession standard
deviations in the normal and PRK groups were 4.9 microm and 3.8 microm, respectively.
CONCLUSIONS: Noncontact central corneal thickness measurements made using the StratusOCT
instrument are accurate and reproducible, both in normal subjects and in post-PRK
patients. The instrument system does not need any modifications to correctly detect
and measure the center of the cornea.