Influence of Manufacturing Tolerance and Formula Thickness Type in the Prediction Error of Multifocal Intraocular...

To assess differences in intraocular lens (IOL) power calculation prediction error (PE) considering the manufacturing tolerance or exact power (EP) versus labeled power (LP), and to compare accuracy using the Barrett formula with optimized constant versus a thick-lens formula.

The PE and absolute PE were calculated for a random eye of patients implanted with the multifocal Liberty Q-Flex 640PM IOL (Medicontur Ltd) considering the LP and the EP provided by the manufacturer. The outcomes for the Barrett with optimized constant formula and a thick-lens formula personalized for the surgeon, biometer, and IOL were compared.

A total of 155 eyes were included in the analysis. The mean absolute tolerance was 0.12 diopters (D) (range: 15.00 to 25.00 D) and 0.19 D (range: 25.00 to 30.00 D). These mean values corresponded to 0.07 and 0.11 D at the corneal plane, respectively (P = .002). Differences in mean PE considering the LP versus EP were 0.05 D or less (P > .05) for both formulas. No differences were found for absolute PE with a magnitude of 0.01 D or less (P < .05). The percentage of eyes within ±0.375 D ranged between 74.2% and 75.5% (P > .05).

The percentage of eyes within ±0.375 D did not increase using EP in comparison to LP in patients implanted with a multifocal IOL with powers ranging from 18.00 to 27.00 D. If the constant is properly optimized, a thick-lens formula also results in no clinically relevant differences versus the Barrett formula.