AIM: To compare biometry results of IOLMaster and contact ultrasound(US)anterior segment parameters, and to evaluate the calculation accuracy and repeatability of intraocular lens power in both.

METHODS: Preoperative measurement of anterior segment parameters were prospectively obtained in 137 eyes of 121 subjects with the IOLMaster compared with the US. Postoperative best corrected visual acuity(BCVA)and the actual diopter were measured.

RESULTS: There was an excellent correlation between IOLMaster and US measurements for the ACD(r=0.823, P<0.01)and AL(r=0.996, P<0.01). 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<0.01). With the 95% limits of agreement(LoA)from -0.08～+0.48mm for ACD and from -0.09～+0.69mm for AL. For IOLMaster, the mean prediction error(MPFE)-0.15±0.38D, the mean absolute prediction error(MAFE)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.

CONCLUSION: Partial coherence biometry using the IOLMaster provides the more accurate and reliable anterior segment parameters measurement values. A high degree of agreement between US and IOLMaster is 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.