Immersion A-scan compared with partial coherence interferometry: outcomes analysis

PURPOSE: To compare 2 methods of axial length measurement, immersion ultrasonography and partial coherence interferometry, and to elucidate surgical outcomes based on immersion measurements.

SETTING: Oregon Eye Institute, Eugene, Oregon, USA.

METHODS: Axial length measurements in 50 cataractous eyes were obtained by optical biometry (IOLMaster, Zeiss Humphrey Systems) and immersion ultrasound (Axis II, Quantel Medical), and the results were compared. Intraocular lens (IOL) power calculations in the same eyes after cataract extraction and posterior chamber IOL implantation were evaluated retrospectively based on the postoperative spherical equivalent prediction error.

RESULTS: Immersion ultrasonography and partial coherence interferometry measurements correlated in a highly positive manner (correlation coefficient = 0.996). Outcomes analysis demonstrated 92.0% of eyes were within +/-0.5 diopter of emmetropia based on immersion axial length measurements.

CONCLUSION: Immersion ultrasonography provided highly accurate axial length measurements and permitted highly accurate IOL power calculations.