Comparison of 2 laser instruments for measuring axial length

PURPOSE: To compare axial length (AL), anterior chamber depth (ACD), and keratometric (K) measurements of 2 laser biometers SETTING: Private practices, Lynwood and Santa Monica, California, USA. METHODS: In this prospective comparative observational study of eyes with cataract and eyes with a clear lens, AL. ACID, and K measurements were performed using an IOLMaster biometer, which uses partial coherence interferometry (PCI), and a Lenstar LS 900 biometer, which uses optical low-coherence reflectometry (OLCR) lntraocular lens (IOL) power calculation was performed using the Haigis formula. The IOL prediction error was calculated for each eye RESULTS: The study evaluated 50 eyes with cataract and 50 eyes with a clear lens There was a good correlation between AL, ACID, and K measurements in the cataractous eyes (r = 0.9993, 0 9667, and 0.9959, respectively) and in eyes with a clear lens (r = 0.9995, 0.8211, and 0 9959, respectively). The OLCR unit measured a slightly longer AL in the cataract group and clear lens group (mean difference 0 026 mm and 0.023 mm, respectively), a deeper ACD (0.128 mm and 0 146 mm, respectively), and a flatter K (-0 107 diopter [D] and -0.121 D, respectively). The differences were statistically significant (P<.0001). The mean absolute error in IOL power prediction was 0.455 D +/- 032 (SD) with the OLCR unit and 0 461 +/- 0.31 D with the PCI unit (P>.1). CONCLUSIONS: Measurements were comparable between the OLCR device and the PCI device A slight decrease (0 050) in the a(0) constant is recommended if the Haigis formula is used