The effect of cycloplegia on the lenstar and the IOLMaster biometry.

Purpose: To evaluate the effect of cycloplegia on ocular biometry measurements and intraocular lens (IOL) power calculation using the Lenstar LS900 (Haag-Streit AG, Koeniz, Switzerland) and the IOLMaster (Carl Zeiss Meditec AG, Jena, Germany) biometers and to assess the agreement between the devices.

Methods: Measurements were taken with the Lenstar and the IOLMaster on 43 healthy volunteers with a mean age of 22.1 ± 4.7 years (range, 18 to 37 years). Axial length (AL), anterior chamber depth (ACD), corneal curvature, and horizontal iris width (white-to-white [WTW]) measurements were performed with and without cycloplegia. The IOL powers were calculated using four formulas: Sanders-Retzlaff-Kraff/Theoretical, Holladay 1, Hoffer Q, and Haigis.

Results: Cycloplegia had no significant effect on AL or corneal curvature. However, ACD and WTW significantly increased postcycloplegia (Lenstar, 0.09 ± 0.06 mm and 0.10 ± 0.17 mm, respectively; IOLMaster, 0.06 ± 0.07 mm and 0.43 ± 0.35 mm, respectively; p <0.001). The Lenstar AL measurements were statistically but not clinically significantly longer than those of the IOLMaster (precycloplegia, 0.03 ± 0.03 mm; postcycloplegia, 0.02 ± 0.03 mm; p < 0.001). For ACD measurements, the 95% limits of agreement were -0.19 to 0.20 mm without cycloplegia and -0.11 to 0.17 mm with cycloplegia. The 95% limits of agreement for WTW measurements were -1.07 to 0.45 mm with cycloplegia. The only significantly different IOL power precycloplegia and postcycloplegia was with the Haigis formula and the Lenstar measurements: 15.12 ± 3.87 diopters and 15.26 ± 3.92 diopters (p < 0.01).

Conclusions: Cycloplegia affected ACD and WTW but not AL or corneal curvature measurements. Generally, good agreement was found between the Lenstar and the IOLMaster, although not for WTW. Differences between these devices do not produce a clinically significant impact on IOL power.