The effect of incision site on surgically induced astigmatism in manual small incision cataract surgery: a systematic review and meta-analysis.

PURPOSE: To ascertain the relationship between surgically induced astigmatism (SIA) and manual small incision cataract surgeries (MSICS) performed through superior or temporal incision and quantify the differences that may exist between them.

METHODS

The protocol was registered in PROSPERO (CRD42024598386). Literature search was conducted across databases including PubMed, Scopus, Embase, and Web of Science. Studies published from January 1990 to January 2025 that reported surgical outcomes of MSICS with either a temporal or superior incision approach, and described SIA corresponding to the incision site were included. Two independent reviewers assessed the titles and abstracts for eligibility based on the predefined inclusion criteria. Data was extracted onto a standard data extraction form. Risk of bias assessment and study quality reporting were performed using NIH quality assessment tools.

RESULTS

The initial search yielded 2,014 articles; after removing duplicates, 831 were screened, 53 underwent full-text review, and 28 were included in the meta-analysis. The pooled mean SIA for the superior incision and temporal incisions were 1.10 D (95% CI: 0.94 to 1.26D) and 0.82 D (95% CI: 0.68 to 0.96D), respectively. A higher mean SIA was noted with straight incision compared to frown incision for both superior (1.14 D vs 1.06 D) and temporal approaches (1.02 D vs 0.72 D). The risk of bias assessment indicated that most studies had a low risk of bias with substantial heterogeneity (I2 = 98.7% for superior incision studies and I2 = 97.05% for temporal incision studies), and no publication bias (Egger's test, p = 0.122).

CONCLUSION

Around 1D of pre-existing astigmatism can be neutralized by placing an appropriate incision along the steep meridian. In the absence of any pre-operative astigmatism, a frown incision placed on the temporal aspect should be preferred since it produces the least SIA. The influence of sutures on SIA needs to be evaluated further.