Network Meta-analysis of Intraocular Lens Power Calculation Formula Accuracy in 1016 Eyes with Long Axial Length

Author: Ma Y, Xiong R, Liu Z, Young CA, Wu Y, Zheng D, Zhang X, Jin G.

Geographical coverage: Not reported

Sector: Intraocular lens

Sub-sector: Myopia

Equity focus: Not reported

Study population: Patients with cataract and an axial length ≥ 26 mm

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background

High myopia—commonly defined as an axial length (AL) of at least 26 mm—is an escalating global public-health issue. Highly myopic eyes develop cataract earlier and progress more rapidly than non-myopic eyes, yet their anatomical differences make accurate intra-ocular lens (IOL) power calculation challenging. Conventional formulae frequently underperform in long eyes, compromising refractive accuracy and visual outcomes. Newer formulae such as Barrett Universal II, Kane, EVO and Olsen, alongside artificial-intelligence and ray-tracing approaches, promise improved precision, but head-to-head evidence is inconsistent, necessitating a robust comparative evaluation.

Objective

To identify the most accurate evidence-based IOL power-calculation formulae for eyes with long AL.

Main findings

Ten studies (1,016 eyes) comparing eleven formulae met the inclusion criteria. Formulae assessed were: Olsen, Kane, Emmetropia Verifying Optical (EVO), Barrett Universal II (BUII), Holladay 1 with Wang–Koch adjustment (H1-WK), Holladay 1 with modified Wang–Koch adjustment (H1-MWK), Radial Basis Function 2.0 (RBF 2.0), Ladas Super Formula (LSF), SRK/T-WK, SRK/T-MWK and Haigis.

*SUCRA = surface under the cumulative ranking curve.

Overall, Olsen, Kane and EVO consistently ranked in the top three and are therefore the most reliable choices for long eyes.

Methodology

Systematic searches of PubMed, Embase, Web of Science and the Cochrane Library (January 2000 – June 2022; English-language) retrieved retrospective and prospective clinical studies of eyes with AL ≥ 26 mm undergoing cataract or refractive-lens surgery with in-the-bag IOL implantation, biometry by IOLMaster, at least two formulae compared, and refraction measured ≥ 1 month post-operatively. Reference lists of included articles and relevant reviews were hand-searched.

Two reviewers independently screened records, extracted data and judged quality with QUADAS-2; disagreements were resolved by discussion or third-party arbitration. Fixed- or random-effects models were selected according to heterogeneity (I² threshold 50 %). A frequentist network meta-analysis generated pooled relative risks for each PE margin. Ranking probabilities and SUCRA values determined the hierarchy of formulae; funnel plots assessed publication bias.

Applicability / external validity

Most studies were small and some included both eyes of individual participants, risking unit-of-analysis bias. Data for extremely long eyes (AL ≥ 30 mm) and for refractive-lens exchange were sparse. Multicentre trials with larger, ethnically diverse cohorts are required to confirm superiority, particularly in extreme myopia.

Geographic focus

No geographic limits were set, but the countries of origin for included studies were not specified.

Summary of quality assessment

Confidence in the review’s conclusions is medium. Searches were thorough, eligibility criteria transparent, and dual-review processes followed. Study characteristics were clearly presented, appropriate statistical methods applied, and heterogeneity explored. Limitations include English-language restriction, absence of an excluded-study list and limited reporting of study provenance.