Repeatability and agreement of ocular biometry measurements: Aladdin versus Lenstar

To assess the repeatability and agreement between the Aladdin and Lenstar biometers.

Three consecutive measurements of the right eye of 102 subjects were acquired by the Aladdin (V.1.1.3) and the Lenstar (V.1.0.3), respectively, with a random order of which biometer to use first. Parameters compared included axial length (AL), anterior chamber depth (ACD), flat keratometry (Kf), steep keratometry (Ks), mean keratometry (Km), J₀, J₄₅ and white-to-white (WTW) distance. Intraocular lens (IOL) power formulas included SRK/T (Sanders-Retzlaff-Kraff/Theoretical), Holladay 1, Hoffer Q and Haigis. Repeatability (S_r), repeatability limit (r) and Bland-Altman limits of agreement (LoA) were calculated.

S_r was marginally better with the Lenstar for AL (0.02 mm), ACD (0.02 mm) and WTW distance (0.07 mm), but S_r was marginally better with the Aladdin for Kf (0.10 dioptre (D)), J₀ (0.07 D) and J₄₅ (0.06 D). In terms of agreement, the mean difference was small and non-statistically significant between the two devices for ACD, Ks and J₄₅. The mean difference for Kf, Km, J₀ and WTW distance were all statistically significantly lower with the Aladdin than the Lenstar for the exception of WTW distance. The Bland-Altman LoA displayed narrow ranges implying good agreement with the exception for WTW distance. For IOL formulas, the mean difference was very small and not statistically significantly different. The LoA were narrow (within 0.50 D), implying acceptable use of each device interchangeably.

High levels of repeatability and agreement were found between the Aladdin and Lenstar suggesting that the devices may be used interchangeably in normal eyes with refractive error.