Comparison of Ultrasound and Scheimpflug Methods for Central Corneal Thickness

Abstract

Aim: The central corneal thickness (CCT) of healthy individuals was measured with an ultrasonic pachymeter (UP) and the Scheimpflug imaging system (SIS) and the results were compared to evaluate the agreement between the two methods in this study. Materials and Methods: The 61 subjects who had no ocular pathology or systemic disease except blepharitis were included in the study. CCT measurements of all subjects were performed with the UP (Sonomed 300P Pacscan) and SIS (Nidek Optical biometer AL-Scan) devices and the results were compared. The t test and the Bland-Altman plot were used as the statistical methods. Results: The study sample consisted of 61 cases including 20 males and 41 females. The mean age was 41.8±12.4 (20-58) years for the males and 46.2±9 (24-60) years for the females with no statistically significant difference (P=0.116). The mean CCT measurement of all the 61 subjects was 544.5±31 µm in the right eyes and 547.3±33 µm in the left eyes with UP, 530.7±27.6 µm in the right eyes and 531.6±25.5 µm in the left eyes with SIS. The CCT in the SIS results was an average of 13.8 μm thinner than the UP results in the right eye, 15.7 μm in the left eye and this difference was statistically significant (p=0.001 in right and left eyes). A high degree of agreement was found between the two methods with the Bland-Altman plot. Conclusion: A high degree of agreement was found between SIS and UP regarding CCT measurements and the mean SIS results were 13.8 μm and 15.7 μm thinner than the UP results in the right eyes and left eyes respectively.