A Comparative Study on the Accuracy of IOL Calculation Formulas in Nanophthalmos and Relative Anterior Microphthalmos.

PURPOSE: We sought to compare the prediction accuracy of 6 intraocular lens (IOL) formulas, namely, the Haigis, Hoffer Q, Holladay I, SRK/T, Barrett Universal II and Hoffer QST formulas, in microphthalmic eyes, including those with nanophthalmos and relative anterior microphthalmos (RAM).

DESIGN

Retrospective case series.

METHODS

Twenty-six eyes with nanophthalmos (axial length [AL] 16.84 ± 1.36 mm, range 15.25 mm-19.82 mm) and 12 eyes with RAM (corneal diameter 8.41 ± 0.92 mm, range 7.00 mm-9.50 mm) receiving cataract surgery were included. The IOL Master 500 was used for biometry; thus, lens thickness (LT) was omitted in the IOL power calculation. The mean and median arithmetic and absolute prediction errors (PEs) of the 6 original calculation formulas, the absolute PEs of the 6 formulas after optimization, and the proportion of PEs within ±0.25 diopters (D), ±0.5 D, ±1 D, and ±2 D with each formula were compared. The factors influencing PE were analyzed by multivariate regression.

RESULTS

In the nanophthalmos group, the overall prediction results were shifted to myopia. The original Haigis formula had the smallest median absolute PE (1.61 D, P < 0.001), and the optimized Haigis formula had the highest proportion of PEs within ±0.25 D, ±0.5 D, and ±1 D. In the RAM group, the overall prediction results were not significantly different from 0 (P > .05). No significant difference was found among the formulas before optimization (P = .146) and after optimization (P = .161), but the optimized Barrett Universal II formula had the highest proportion of PEs within ±1 D and ±2 D.

CONCLUSIONS

When omitting the LT parameter in the calculation, the Haigis formula was the most accurate in cataract patients with nanophthalmos (AL <20 mm) among the 6 IOL calculation formulas, and the Barrett Universal II formula had the highest accuracy in cataract patients with RAM (corneal diameter ≤9.5 mm).