Effect of image-guided systems in phacoemulsification with intraocular lens (IOL) implantation: a systematic review and meta-analysis

Author: Su Y, Fu M, Chen Y, Qiao R, Yi GG.

Geographical coverage: China, India, Germany, the US, Egypt, and the Netherlands

Sector: Intraocular lens

Sub-sector: Image-guided systems

Equity focus: Not reported

Study population: Patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Cataract, characterised by clouding of the eye’s natural lens, is a leading cause of blindness worldwide. Surgery is the primary treatment method. Many cataract patients also present with corneal astigmatism, which can affect postoperative visual outcomes. Toric intraocular lens (IOL) implantation corrects both conditions, but precise alignment is crucial. Manual marking is a commonly used technique. However, advances in digital technology have introduced image-guided systems for greater precision. These systems assist with incision planning, capsulorhexis, and toric IOL alignment. Studies show mixed results: some show improved outcomes, while others find no significant difference compared to manual marking.

Objective:

To identify, evaluate and summarise the available evidence to determine whether image-guided systems significantly improve outcomes in phacoemulsification with IOL implantation.

Main findings:

The review included 14 studies (885 eyes in total: 469 in the image-guided group and 416 in the manual group) published between 2014 and 2019. Methodological quality varied significantly, with risk of bias ranging from low to high across different domains, particularly in patient selection and blinding procedures.

Preoperative outcomes showed no significant differences in uncorrected distance visual acuity [UDVA] (standardised mean difference, SMD: 0.25, 95% confidence interval [CI]: -0.21 to 0.70, I² = 77%, p = 0.29), best corrected visual acuity [BCVA] (SMD: -0.10, 95% CI: -0.27 to 0.08, I² = 37%, p = 0.28), or cylinder (WMD: 0.03, 95% CI: -0.05 to 0.10, I² = 19%, p = 0.48) between the image-guided and manual groups.

Postoperative outcomes showed no significant differences in UDVA (SMD: -0.11, 95% CI: -0.32 to 0.11, I² = 59%, p = 0.33), BCVA (SMD: 0.03, 95% CI: -0.12 to 0.18, I² = 36%, p = 0.72), corneal cylinder (WMD: 0.13, 95% CI: -0.06 to -0.32, I² = 0%, p = 0.17), or intraocular pressure (IOP) (WMD: -0.37, 95% CI: -1.36 to -0.62, I² = 9%, p = 0.46) between the image-guided and manual groups. However, there was less residual refractive cylinder in the image-guided group than in the manual group (WMD: -0.20, 95% CI: -0.26 to -0.14, I² = 59%, p < 0.00001). Image-guided systems resulted in more accurate toric IOL alignment (WMD: -1.20, 95% CI: -1.43 to -0.96, I² = 14%, p < 0.00001).

Methodology: The searches were performed in PubMed, Embase, and China National Knowledge Infrastructure from the inception of these databases through January 20, 2021 to identify cohort studies on patients undergoing cataract surgery with toric IOL implantation. The studies were included if they used both image-guided and manual marking techniques for toric alignment during surgery, and included eyes with a corneal cylinder of at least 1.00 D. No language limits were applied.

Two reviewers independently screened the identified studies. Any disagreements between reviewers were resolved by consulting a third reviewer. Relevant data were extracted for each included study. Methodological quality of the included studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. The findings were synthesised using a fixed- or random-effects model meta-analysis depending on heterogeneity. Heterogeneity was assessed using the I² statistic. A sensitivity analysis was conducted to assess the influence of a single study on the pooled estimates. Subgroup analyses were conducted for different follow-up durations.

Applicability/external validity: The review acknowledged the small sample sizes and variability in both image-guided and manual marking techniques across studies, along with differences in study quality, blinding, and outcome reporting. It emphasised the need for large-scale, high-quality trials to strengthen the generalisability of the findings.

Geographic focus: The review did not apply any geographic limits. The included studies were conducted in China, India, Germany, the US, Egypt, and the Netherlands.

Summary of quality assessment:

Overall, there is medium confidence in the review’s conclusions. The database search for literature was comprehensive, with clearly defined inclusion and exclusion criteria. Study quality was assessed using valid and reliable tools, and the findings of these assessments were reported. Two reviewers independently screened the articles. Characteristics of the included studies were presented, and the data were synthesised using meta-analysis. Heterogeneity was assessed using the I² statistic. Subgroup and sensitivity analyses were also performed. However, the review did not provide a list of excluded studies, nor did it report whether the reference lists of included studies were checked. The findings were not stratified by risk of bias, and it was unclear how many reviewers independently extracted data.