Comparative meta-analysis of toric intraocular lens alignment accuracy in cataract patients: Image-guided system versus manual marking

Authors: Zhou F, Jiang W, Lin Z, Li X, Li J, Lin H, Chen W, Wang Q. 

Geographical coverage: Not reported

Sector: Diagnosis

Sub-sector: Accuracy

Equity focus: Not reported

Study population: Patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Recent advancements in surgical techniques and intraocular lens (IOL) design have raised expectations for spectacle independence following cataract surgery. However, corneal astigmatism greater than 1.00 dioptre (D) remains a common challenge that can impair visual outcomes. Toric IOLs are used to correct astigmatism, but accurate alignment is crucial—small rotational misalignments can significantly reduce corrective effectiveness. Misalignment can arise from several sources, with corneal marking being a modifiable factor. Both manual and image-guided techniques are commonly used, but their relative accuracy remains uncertain. Some studies favour image-guided systems, while others find no substantial difference. This meta-analysis was conducted to assess which method delivers better alignment accuracy.

Objectives: To evaluate the accuracy of image-guided versus manual corneal marking techniques for toric IOL implantation, and to determine the superior approach for clinical practice.

Main findings:

A total of five studies (257 eyes) published between 2015 and 2018 were included in the meta-analysis. Four studies were prospective randomised trials and one was a retrospective randomised study. All were assessed as high quality.

Key findings:
– Image-guided marking significantly reduced axis misalignment compared to manual marking (weighted mean difference [WMD]: -1.33 degrees, 95% confidence interval [CI]: -1.88 to -0.79 degrees, P < 0.00001).
– Postoperative astigmatism was also significantly lower in the image-guided group (WMD: -0.14 D, 95% CI: -0.24 to -0.05 D, P = 0.003).
– No significant differences were found between groups in preoperative corneal cylinder (WMD: 0.06 D, 95% CI: -0.16 to 0.28 D, P = 0.59), toric IOL misalignment within five degrees (odds ratio: 1.34, 95% CI: 0.56 to 3.23, P = 0.51), or uncorrected distance visual acuity (UDVA) (WMD: 0.02, 95% CI: -0.04 to 0, P = 0.13).

Methodology:

The authors searched PubMed, Embase, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials for English-language studies published up to 30 November 2018. Included studies examined toric IOL implantation in eyes with at least 1.00 D of corneal astigmatism and compared image-guided versus manual marking techniques. Reference lists of included articles were screened for additional studies.

Two reviewers independently screened studies, resolving discrepancies through discussion or arbitration by a third reviewer. Data were extracted independently by three reviewers, with disagreements resolved by a fourth. Study quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Results were synthesised using fixed or random-effects models depending on heterogeneity, which was evaluated using I² statistics. Funnel plots and Egger’s test were used to assess publication bias. Sensitivity and subgroup analyses were performed when I² exceeded 50%.

Applicability/External Validity

While the review did not explicitly address applicability, it highlighted the use of multiple image-guided systems (e.g., Verion, Callisto Eye, TrueVision 3D) and manual marking techniques (e.g., pendulum, bubble, direct visualisation), indicating practical relevance across diverse clinical settings. The authors acknowledged limitations due to small sample sizes and study design variability and called for larger, standardised studies.

Geographic focus:

The review did not report the geographic locations of the included studies and did not apply geographical restrictions.

Summary quality assessment:

The review’s conclusions are of medium confidence. While the methodological quality of included studies was high, the restriction to English-language publications introduces potential bias and may have excluded relevant studies published in other languages.