Agreement between lens thickness measurements by ultrasound immersion biometry and optical biometry

Purpose: To compare lens thickness measurements provided by immersion ultrasound (US) biometry and optical biometry. Setting: IRCCS-Fondazione Bietti, Rome, Italy. Design: Evaluation of diagnostic technology. Methods: Immersion US biometry and optical biometry were performed in a consecutive series of eyes having cataract surgery. Three optical biometers (OA-2000, Aladdin, and Galilei G6) were used. To assess how the differences in lens thickness measurements influenced intraocular lens (IOL) power calculation, the lens thickness values were entered into the Olsen formula. Results: Eighty-eight eyes were analyzed. Ultrasound immersion biometry yielded significantly higher lens thickness values than all of the optical biometers (P < .0001). The mean difference ranged between 0.29 mm and 0.43 mm. Although the differences between the 3 optical biometers were smaller, they were still statistically significant (P < .001). With respect to the immersion US biometry, lens thickness measurements using the optical biometric measurements would have resulted in the selection of a lower IOL power in between 43.2% and 62.5% of eyes, depending on the optical biometer. Comparison of the measurements of the 3 optical biometers showed that a different IOL power would have been selected in between 9.1% and 19.3% of eyes. Conclusions: Lens thickness measurements by immersion US biometry and optical biometry cannot be considered interchangeable. Minor, but still significant, differences between the 3 optical biometers tested were also found.