Efficacy of segmented axial length and AI approaches to IOL power calculation in short eyes.

PURPOSE: In short eyes, to compare the predictive accuracy of newer intraocular lens (IOL) power calculation formulas using traditional and segmented axial length (AL) measurements.

SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, TX and East Valley Ophthalmology, Mesa, AZ.

DESIGN: Multi-center retrospective case series.

METHODS: Measurements from an optical biometer were collected in eyes with AL < 22mm. IOL power calculations were performed with 15 formulas using two AL values: 1) machine-reported traditional AL (Td-AL) and 2) segmented AL calculated with the Cooke-modified AL nomogram (CMAL). One AL method and seven formulas were selected for pairwise analysis of mean absolute error (MAE) and root mean square absolute error (RMSAE).

RESULTS: The study comprised 278 eyes. Compared with the Td-AL, the CMAL produced hyperopic shifts without differences in RMSAE. The ZEISS AI IOL Calculator (ZEISS AI), K6, Kane, Hill-RBF, Pearl-DGS, EVO, and Barrett Universal II (Barrett) formulas with Td-AL were compared pairwise. The ZEISS AI demonstrated smaller MAE and RMSAE than the Barrett, Pearl-DGS, and Kane. K6 had a smaller RMSAE than the Barrett formula. In 73 eyes with shallow anterior chamber depth, the ZEISS AI and Kane had a smaller RMSAE than the Barrett.

CONCLUSIONS: ZEISS AI outperformed Barrett, Pearl-DGS, and Kane. The K6 formula outperformed some formulas in selected parameters. Across all formulas, use of a segmented AL did not improve refractive predictions.