Comparison of central corneal thickness and anterior chamber depth measurements using the Anterior Segment Optical Coherence Tomography and A-scan ultrasonography

Abstract

Objective To assess central corneal thickness(CCT)and anterior chamber depth (ACD) measurements with anterior segment optical coherence tomography (AS-OCT)comparing with A-scan ultrasonography (A-scan US).Methods 54 eyes of 33 normal subjects were enrolled in the study.CCT and ACD were measured using AS-OCT and A-scan US.The measurements of two instruments were analyzed using paired t test,Pearson correlation and Bland-Altman plot,respectively.Results The CCT of AS-OCT and A-scan US were 524.41± 23.24 microm and 513.37± 22.7 microm,respectively.The CCT values measured by A-scan US were significantly greater than AS-OCT, paired difference was 11.04± 5.10 microm (t =15.906, P =0.000).There were a significantly correlation between CCTs value of two instruments (r =0.976, P =0.000). The 95% LoA (95% Limts of Agreement)was -21.03 microm to -1.04 microm.The width of 95% LoA was 28 microm,3.81% of the average pachymetry reading.The ACD of AS-OCT and A-scan US were 2.89± 0.29 mm and 3.18 ± 0.26 mm,respectively.The ACD values measured by AS-OCT were significantly greater than A-scan US, paired difference was -0.29± 0.17 mm(t =-12.052, P = 0.000).There were a significantly correla-tion between CCTs value of two instruments(r=0.803 ,P=0.000).The 95% LoA was -0.63 mm to -0.06 mm.The width of 95% LoA was 0.57 mm, 19.72% of the average A-scan reading.Conclusion CCT and ACD measured by AS-OCT were highly correlated with that from ultrasound pachymetry.ln comparison with measurements of A-scan,CCT value of AS-OCT was lower,and the ACD was deeper.However,ACD readings by AS-OCT and A-scan were consistently less than that of CCT. Key words: Central corneal thickness; Anterior chamber depth; Reproducibility; Optical Coherence Tomography