AIM: To compare the measurement of anterior segment parameters by partial coherence interferometry(PCI)and contact ultrasonic(US)axial scan(A-scan). The accuracy in predicting postoperative refraction and the reproducibility of each biometry measurement were also estimated in a prospective study of eyes that underwent phacoemulsification with IOL implantation.

METHODS: Preoperative measurement of anterior segment parameters were prospectively obtained in 137 eyes of 121 subjects with the PCI compared with the US. The postoperative best corrected visual acuity and postoperative refraction were obtained and compared with each biometric method.

RESULTS: There was an excellent correlation between PCI and US measurements for the anterior chamber depth(ACD; r=0.823; P<0.001)and axial length(AL; r=0.996; P<0.001). The mean values of the parameters measured by IOLMaster and US were, respectively, as follows: ACD, 2.94±0.49mm, 2.69±0.51mm; AL, 24.17±1.64mm, 23.81±1.83mm. The mean differences of ACD and AL values between IOLMaster and US measurements were 0.25±0.22mm, 0.36±0.24mm respectively, proved to be statistically significant(P<0.001). With the 95% limits of agreement from -0.08mm to +0.48mm for ACD and from -0.09mm to+0.69mm for AL. For IOLMaster, the mean prediction error -0.15±0.38D, the mean absolute prediction error was 0.29±0.27D with 96% of the eyes within 1D from the predicted refraction. Applanation ultrasonography after optimisation yielded a greater absolute prediction error than the IOLMaster biometry, 0.41±0.38D with 88% of the eyes within 1D from the predicted refraction. For IOLMaster biometry, the intraobserver variability(SD)was ±25.6μm for AL, ±33.4μm for ACD and ±12.9μm for corneal radius. The coefficients of variation(COV)were 0.11%, 0.52%, and 0.17%, respectively. The interobserver variability(SD)was ±21.5μm for AL, ±29.8μm for ACD and ±15.9μm for corneal radius. The COV were 0.09%, 0.62%, and 0.21%, respectively. The reliability was 99.9% for AL, 97.8% for ACD, and 99.8%/99.5% for corneal radius(r₁/r₂).

CONCLUSION: PCI using the IOLMaster provides the more accurate and reliable anterior segment parameters measurement values. A high degree of agreement between US and IOLMaster was noted. The IOLMaster not only has the advantage of performing noncontact examinations, but also produces various additional data simultaneously and may thus obviate the need for multiple examinations.