Prediction error in low power intraocular lens in highly myopic eyes

To assess refractive prediction error (RPE) after cataract surgery in highly myopic eyes, focusing on the accuracy of intraocular lens (IOL) power calculations using the SRK/T formula without axial length adjustment.

Tertiary ophthalmology department at Lariboisière Hospital, Paris, France. Retrospective observational study.

We reviewed the records of eyes with axial length ≥ 26.5 mm that underwent cataract surgery between January 2019 and December 2021. RPE was defined as the difference between achieved and predicted spherical equivalent using SRK/T. We analyzed the absolute prediction error, proportion of eyes within ± 0.5D of target, and the direction of the error (hyperopic/myopic). Subgroup analyses were performed based on IOL power, especially plano and negative lenses, and the impact of implant-specific A-constant adjustments. Results were compared with predictions from the Barrett II and Pearl-DGS formulas.

A total of 102 eyes from 71 patients were included. 61% achieved RPE within ± 0.5D. The mean absolute error was + 0.50 ± 0.49 D. Distribution of the signed prediction error showed a 60% hyperopic shift. The plano/negative IOL subgroup (n = 26) showed a significantly higher RPE (+ 0.93 ± 0.68 D, p < 0.001), with a hyperopic shift in 85% of cases. This was associated with IOLs lacking optimized A-constants with SRK-T formula at low/negative power. Barrett II (0.56 ± 0.36 D) and Pearl-DGS (0.57 ± 0.45 D) significantly reduced RPE and hyperopic shift in this subgroup (p < 0.05).

SRK/T exhibited a frequent hyperopic shift in highly myopic eyes, driven primarily by the poor performance with plano and negative power meniscus IOLs. This highlights the clinical need for optimizing A-constants for SRK-T formula at low powers and mandates the routine use of modern formulas like Barrett II or Pearl-DGS in this specific population.