corneal pachymetry using ultrasound vs orbscan ii in normal and post-lasik eyes

purpose: to compare orbscan ii (o ii) and ultrasound (us) pachymetry in normal and post-lasik eyes. methods: in a comparative prospective study, central corneal thickness (cct) was measured in 168 eyes of 84 normal subjects and 42 eyes without corneal opacity of 21 post-lasik patients by o ii and us. paired t test was used to identify significant differences between the two methods and pearson test was used to identify the correlation of measurments between the two methods. results: mean cct measured by ultrasound (538.7 ± 47.4 mm) was less than that of o ii (542.7 ± 52.2 mm) in the normal eyes (p<0.04), but mean cct measured by ultrasound (477.8 ± 38.2 mm) was greater than that of o ii (469.5 ± 47.2 mm) in the post-lasik eyes. (p<0.02) there was significant linear correlation between us and o ii in both groups. (r=0.87, p=0.000 and r=0.88, p=0.000, respectively). conclusion: mean difference of cct measurements between o ii and us in normal and post-lasik clear cornea is not clinically significant and interchangeable use of data in planning or assessing corneal surgery is possible.