Comparison of central corneal thickness using anterior segment optical coherence tomography vs ultrasound pachymetry.
OBJECTIVE
To determine if there is a systematic difference in central corneal thickness (CCT) measured using anterior segment optical coherence tomography (AS-OCT) as compared with ultrasound pachymetry.


METHODS
Prospective observational study.


METHODS
Consecutive subjects with clinically normal corneas underwent CCT measurement by both ultrasound and AS-OCT while participating in a population-based study in Ghana, West Africa. One eye of each subject was randomly selected for analysis. Two measurements were taken and averaged. Agreement and interobserver variability were also analyzed.


RESULTS
One hundred and fifty-five subjects of African ethnicity and average age 57 years (standard deviation [SD] 12; range, 40 to 98 years) were included. Measurements by AS-OCT and US were taken a mean of 15 days (maximum, six weeks) apart. The mean (SD) [range] US CCT was 525.3 microm (33.5) [422, 653] and 499.0 microm (32.0) [428, 613] with AS-OCT. Measurements by the two modalities were strongly correlated (r(2) = 0.82; P < .001), and a significant difference was observed between mean US and AS-OCT CCT (SD) [range] of 26.3 microm (14.2) [-63, 12] (P < .001). The width of the limits of agreement was 28 microm, about 6% of the average pachymetry reading. In 50 eyes randomly remeasured with OCT by a second observer, the intraclass correlation coefficient was 0.91. There was a small but significant systematic difference between observers (mean 6.9 microm, SD 10.9 microm), or 1.4% (P < .001), increasing the difference noted above.


CONCLUSIONS
There is a reproducible systematic difference between CCT measurements taken with ultrasound and OCT. It is important to note in clinical practice, that measurements acquired by these two modalities are not directly interchangeable.
Department of Ophthalmology, Stanford University, Stanford, CA, USA.
Hanna Y
HY
Kim
Donald L
DL
Budenz
Pak S
PS
Lee
William J
WJ
Feuer
Keith
K
Barton
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000867:Anterior Chamber / Q000033:anatomy & histology; D001699:Biometry; D044383:Black People / Q000208:ethnology*; D001837:Body Weights and Measures; D003315:Cornea / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D005869:Ghana / Q000208:ethnology; D006801:Humans; D033401:Microscopy, Acoustic / Q000379:methods*; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*