Comparatire study of anterior segment parameters measurement by OCT, Orbscan, and A-scan ultrasound

Objective To compare the accuracy of anterior segment OCT with Orbscan and A ultra-sound in measuring anterior segment parameters.Methods Anterior segment parameters in 66 eyes of 33 my-opic patients were measured with OCT, Orbscan and A-scan ultrasound.The central corneal thickness (CCT), anterior chamber depth (ACD)were acquired by the three methods, corneal diameter( W to W ), anterior cham-ber width,pupil diameter,and anterior chamber angle were measured by OCT and Orbscan.Results The CCTs were (532.32±35.26)μm,(538.45±38.31 )μm,and (555.82±37.63)μm,measured by AS-OCT, Orbscan,and A-scan ultrasound.There were significant differences between each of them (P <0.01 ),and also positive correlations were found.The ACD were ( 3.19±0.21 )mm, ( 3.08±0.24 )mm, and( 3.27±0.23 )mm, re-spectively measured by OCT, Orbcan and ultrasound.There were significant differences between each of them. Pupil diameterwere(5.5±0.93)mm,and(4.5±0.75)mm measured by OCT and Orbscan, The difference was(-1.00±0.68)mm,asignificantdifferencewasfound(t=1195,P=0.000),95%CI(0.84,1.17). Thedifferenceofanteriorcham-beranglewere 1.58° inposition 180° (P=0.119)and 2.89° in position 0° (P<0.01)measure by OCT and Orbscan.Conclusion The CCT was thinner obtained by OCT than by Orbscan and A-scan ultrasound,ACD was deeper than by Orbscan and more close to A-scan ultrasound.The anterior chamber angle were similar in both instruments. AS-OCT provide noncontact,rapid,simple and accurate anterior segment parameters and furthermore a clear ante-rior segment image.It is a useful instrument in measuring anterior segment parameters. Key words: AS-OCT, OrbscanⅡ, A-scan ultrasound, Central corneal thickness, Anterior chamber depth, Anterior chamber angle