To compare the refractive absolute error when axial length (AL), anterior chamber depth (ACD) and keratometry (K) are sourced from different measuring devices (IOL Master vs a combination of automated keratometer and A-scan) and inputted into the Barrett Universal II or SRK/T formula.

This was a retrospective study. Medical charts of eyes that underwent uncomplicated phacoemulsification with in-the-bag implantation of Envista or multifocal FineVision IOL were reviewed. The results of manifest refraction at 1 month after surgery were collected. The predicted refraction corresponding to the IOL power implanted was collected from 4 IOL sheets: using the SRK/T with AL, ACD, and K from IOL Master (Group A); SRK/T formula with AL and ACD from A-scan and K from the automated keratometer (Group B); Barrett formula with AL, ACD and K from IOL Master (Group C); and Barrett formula using with AL, ACD from A-scan and K from automated keratometer. For each group, the absolute error, prediction error, and variances of prediction error were computed.

A total of 132 eyes were included in the study: 56 in the monofocal group and 76 in the multifocal group. The means of manifest refraction spherical equivalent (MRSE) were 0.06 ± 0.38 D and –0.08 ± 0.31 D in the monofocal and multifocal groups, respectively. When AL and K were obtained from various sources and entered into the Barrett formula, the mean absolute error difference in both the monofocal (p = 0.70) and multifocal (p = 0.10) groups did not reach statistical significance. If the SRK/T formula was used, similar outcomes were observed (monofocal p = 0.97; multifocal p = 0.37). When compared to A-scan groups, the prediction error variances are significantly smaller in the groups that used the IOL Master as their data source. Among the four groups, the Barrett group using IOL Master as the data source showed the lowest overall variation of prediction error (monofocal F = 0.04; multifocal F = 0.03).

Though the refractive outcomes may not be statistically different, using the IOL Master as the source of AL and K makes the refractive outcomes more consistent and predictable. Combining the AL and K from the IOL Master with the Barrett Universal II formula further increases the predictability of refractive outcomes.