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

Placing a clear-corneal incision on the steep meridian is sometimes used to reduce low preoperative astigmatism during phacoemulsification. The strategy assumes that the incision mainly flattens its own meridian. This retrospective study asked whether that behavior persists when the wound is closed with one 10-0 nylon suture that is removed at one week. The series included 345 right eyes operated on by one surgeon through a superior or temporal 2.20- or 2.75-mm clear-corneal incision.

How the evidence was produced

A cohort study describes how outcomes are associated with an exposure or treatment in an observed clinical population. This design is useful for routine practice, uncommon events and longer follow-up, but it remains vulnerable to confounding by indication, baseline risk differences and missing data. An association should not automatically be interpreted as a causal effect.

Key result Surgically induced astigmatism was decomposed into a flattening component along the incision meridian and perpendicular torque. The primary steep-axis analysis included eyes whose preoperative steep meridian was within ±20° of the incision: 96 superior and 66 temporal cases. Mean flattening was negative, indicating slight steepening: −0.17±0.56 D for superior incisions (p<0.001) and −0.20±0.73 D for temporal incisions (p=0.059). Perpendicular torque was larger at 0.50 and 0.40 D, respectively, and the final SIA meridian deviated about 52–55° from the incision. For a 2.75-mm superior incision, centroid SIA was 0.50 D at 41°. Individual SIA ranged from 0 to 2.04 D. Of the biometric variables studied, only white-to-white independently predicted the effect.

How to interpret the result

In this series, a sutured steep-axis incision did not deliver the expected meridional flattening. Much of the change was torque, which may fail to reduce the original cylinder and can sometimes worsen it. Clinically, published SIA values for unsutured wounds should not be assumed to apply when an incision requires a stitch. The mean also conceals wide individual variation. The study does not prove that the suture caused the pattern; suture position and tension, removal, wound geometry and healing may all contribute. A center using this approach for low astigmatism should audit its own SIA centroid. More substantial cylinder still requires a separately planned correction rather than reliance on incision placement alone.

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

This was a retrospective, single-surgeon study restricted to right eyes, with no concurrent unsutured control group. Every incision was sutured and the stitch was removed after one week, limiting transfer to routine modern sutureless phacoemulsification. Combining superior and temporal locations and two incision widths introduces heterogeneity, while the steep-axis subgroups were smaller than the full cohort. Wide individual dispersion limits prediction for one patient. Check the full paper for keratometry timing and device, eligibility criteria, suture technique and tension, subgroup comparability, repeated-measure handling, vector sign conventions, confidence intervals, missing data, complications, funding and conflicts.

What to verify in the source

Use the DOI below to verify the complete methods, result tables, funding disclosures and conflicts of interest.