Orbscan System for Measurement of Corneal Thickness

ABSTRACT

PURPOSE: To investigate the accuracy of Orbscan system in measuring corneal thickness before refractive surgery, the authors conducted a comparative study of Orbscan system and ultrasonic pachymeter in their agreement and repeatability. METHODS: 84 patients (168 eyes) who were examined between December, 2000 and March, 2001 were divided into two groups those who exceeded -6.00 D, and those who did not. Orbscan and ultrasonic pachymeter were employed. Correlation and regression were analyzed to assess their agreement. The repeatability was measured by analyzing mean, standard deviation, and 95% confidence interval of each method. RESULTS: The average central corneal thickness was 542.3+/-34.2micro meter by Orbscan system, and 528.6+/-29.7micro meter by ultrasonic pachymeter. Correlation coefficient was nearly 1 between them, and therefore we obtained statistically significant linear regression equation. In the analysis of repeatability, 95% confidence interval of Orbscan system was -17.2micro meter~+11.8micro meter which was superior to the interval of ultrasonic pachymeter (-23.2micro meter~+14.4micro meter). CONCLUSION: Orbscan system measurements of corneal thickness was greater than ultrasonic pachymeter measurements by 9 to 19 m. Because Orbscan system also showed superiority in repeatability, it may be a useful method in the clinical field.