Clinical context

Cataract surgery outcomes are not defined by best-corrected visual acuity alone. Refractive accuracy, vision at different distances, spectacle dependence, contrast sensitivity, dysphotopsia and procedural safety all matter. Corneal and macular status, capsular support, cataract density and IOL calculation also shape the final result. A statistically convincing average therefore still has to be interpreted against the characteristics of an individual eye.

What was studied

After implantation, the IOL optical center may not coincide with the visual axis. A small displacement may be silent with one lens yet reduce image quality with another. This systematic review examined optical benches and ray tracing rather than patient cohorts. PubMed, Scopus and Google Scholar were searched for English-language work from twenty years. Outcomes included modulation transfer function, Strehl ratio, wavefront aberrations and point-spread function for monofocal, EDOF, multifocal and toric lenses.

How the evidence was produced

A systematic review is valuable because it uses a transparent search and predefined criteria to assess the available literature. Reliability depends on search completeness, study selection, risk-of-bias assessment and the quality of included evidence. A broad review cannot remove limitations in the primary studies or turn heterogeneous evidence into a universal recommendation.

Key result Seventy-four studies were included. Aspheric monofocal IOLs with negative spherical aberration generally lost more optical quality during decentration than spherical models. Multifocal and EDOF lenses were also sensitive, with larger displacement reducing modeled image quality and contrast. Toric lenses were particularly affected when displacement occurred together with rotational misalignment. The review does not provide one safe threshold in millimeters: response depended on the specific optical profile, aperture, model eye and measurement method. Findings therefore cannot be reduced to a rule that applies to every lens within a broad class.

How to interpret the result

The review can inform lens selection when capsular stability, angle kappa or unusual anatomy raises concern about centration. After surgery, halos or reduced contrast should be assessed alongside refraction and ocular surface status with attention to IOL position. A bench demonstrates potential degradation; it does not prove that a patient will perceive symptoms or benefit from repositioning.

The result should be understood as an estimate for the population studied, not a promise of an individual outcome. Statistical and clinical significance, absolute and relative effects, and prespecified and exploratory analyses should be distinguished. When several endpoints or subgroups are reported, the prespecified primary endpoint for which the study was designed usually provides the most reliable inference.

Clinical applicability

This evidence is most useful as a basis for preoperative discussion and surgical planning. It helps identify which outcomes should be measured and which trade-offs should be explained to patients. The average effect should not be generalized to every IOL, technique or patient without checking eligibility criteria, surgeon experience, biometry, ocular comorbidity and duration of follow-up.

Limitations

Studies varied in model eyes, pupil size, wavelength, displacement and quality criteria. Only English-language bench studies were included, and Google Scholar limits reproducibility. Clinical outcomes were not pooled and no surgical threshold was established. EDOF and multifocal categories contain different optics. Verify the search, quality assessment, model-specific tables, tilt versus decentration, simulation conditions, conflicts and clinical links in the source.

Beyond the limitations acknowledged by the authors, confidence is affected by sample size, follow-up duration, missing data, choice of comparator and relevance of the outcomes to routine care. Uncommon complications may remain undetected even in a well-conducted study. External validity is reduced when participants, equipment or investigator expertise differ substantially from everyday settings.

What to verify in the source

In the full paper, verify the protocol, eligibility criteria, baseline group characteristics, primary endpoint definition, confidence intervals, adverse events and losses to follow-up. Funding, conflicts of interest, trial registration and consistency between the published analysis and the original plan deserve separate attention. The DOI or source link below provides access to the primary publication for this check.