Effect of intraocular lens material and haptic design on anterior capsule contraction after cataract surgery: A systematic review and meta-analysis

Author: Chen L, Zhong Y, Yao K, Fu Q.

Geographical coverage: Japan, China, Korea, Australia, France, Germany, and the UK.

Sector: Cataract surgery

Sub-sector: Anterior capsule contraction

Equity focus: Not reported

Study population: Patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Globally, cataract is a major cause of blindness, affecting at least 94 million people by 2021, with projections of over 30 million cases in the U.S. alone by 2028. While cataract surgery with intraocular lens (IOL) implantation is highly effective, the anterior capsule contraction (ACC) remains a notable mid-to-late postoperative complication. The ACC, driven by the wound-healing response of residual lens epithelial cells, is influenced by IOL material and design. Moreover, conflicting evidence exists regarding whether hydrophilic or hydrophobic IOLs cause more contraction. Similarly, studies are divided on the impact of haptic design, with some suggesting four-haptic designs reduce ACC more effectively. The lack of consensus highlights the need for a systematic comparison of IOL characteristics which influence ACC outcomes.

Objective: To compare ACC after cataract surgery with the implantation of IOLs of different materials and designs.

Main findings: The review included 13 studies, involving 3339 eyes, published between 1997 and 2022. Eight studies were included in the quantitative synthesis, and seven studies were included in the information summary. The included studies were conducted in Japan (n=3), China (n=2), Korea (n=3), Australia (n=2), France (n=1), Germany (n=1), and the UK (n=1). The quality of the included studies was generally high.

The analysis included eight studies, five randomised controlled trials and three cohort studies, covering a total of 1,221 eyes. The primary outcome measured was the change in the area of the anterior capsule opening over time after surgery. Results consistently demonstrated that hydrophilic IOLs were associated with significantly greater anterior capsule contraction compared to hydrophobic IOLs at all evaluated timepoints: one month, three months, six months, and one year postoperatively.

At one month following cataract surgery, the standardised mean difference (SMD) in capsule contraction was –0.73 (95% confidence interval [CI]: –0.93 to –0.52) for the hydrophilic IOL group, indicating substantial contraction. In contrast, the SMD for the hydrophobic group was –0.57 (95% CI: –0.74 to –0.40). This trend was even more pronounced at the three-month mark, where the hydrophilic group showed an SMD of –1.04 (95% CI: –1.32 to –0.75), while the hydrophobic group showed an SMD of –0.58 (95% CI: –1.01 to –0.16). At six months, the anterior capsule opening area continued to decrease, with an SMD of –0.99 (95% CI: –1.24 to –0.74) in the hydrophilic group, compared to –0.65 (95% CI: –0.92 to –0.38) in the hydrophobic group. By one year postoperatively, the SMD was -1.33 (95% CI: –2.50 to –0.16) for hydrophilic IOLs and –1.27 (95% CI: –2.40 to –0.14) for hydrophobic IOLs. These data clearly demonstrate a greater degree of ACC associated with hydrophilic IOLs over time. Meta-regression confirmed that ACC increased over time in both groups (hydrophilic: P = 0.046; hydrophobic: P = 0.050). In 3 studies that reported absolute change, hydrophilic IOLs induced greater contraction than hydrophobic IOLs (SMD = 0.61, 95% CI: 0.34 to 0.88).

Seven additional studies were reviewed qualitatively. These studies showed mixed results. Four studies reported that haptic design influenced ACC: IOLs with four haptics or plate haptics generally showed less contraction, while modified C-haptic IOLs exhibited more contraction than modified L-haptics. However, three studies found no significant effect of haptic design on ACC.

Methodology:

The searches were conducted in Medline, Embase, ClinicalTrials.gov, and Web of Science up to 1^st January 2023 to identify clinical trials and observational studies involving patients undergoing their first cataract surgery and comparing the hydrophilic and hydrophobic IOLs. The studies published in English and reporting the evolution of the anterior capsule opening area postoperatively were included in this review. The reference lists of relevant review articles were also scanned to identify additional relevant publications.

Two reviewers independently screened the articles, extracted the relevant data and critically appraised the quality of the included studies using the Jadad Scale for clinical trials and the Newcastle–Ottawa Scale for cohort studies. Disagreements between the reviewers were resolved through group discussion. The findings were synthesised using a random-effects model meta-analysis. Heterogeneity was assessed using I² statistics, and publication bias using a funnel plot and Egger’s and Begg’s test. Sensitivity analysis was conducted to explore the effect of a single study on the overall results.

Applicability/external validity: The review did not explicitly discuss the applicability or external validity of its findings. However, it acknowledged variability in study designs, patient populations, and surgical techniques. Additionally, the authors were unable to analyse potential confounders due to limited data. They emphasised the need for future studies to control variables more rigorously, particularly regarding haptic design, to better clarify its impact.

Geographic focus: The review did not apply any geographical limits. The included studies were conducted in Japan, China, Korea, Australia, France, Germany, and the UK.

Summary of quality assessment: Overall, there is medium confidence in the study’s conclusions. The searches were comprehensive and performed in PubMed and Embase with no language restrictions. Inclusion and exclusion criteria were clearly stated. Two reviewers independently screened and assessed study quality using validated tools. Disagreements were resolved by discussion or a third reviewer. Meta-analyses were appropriately conducted and heterogeneity addressed. However, the review did not list excluded studies or report grey literature searches, reference list checks, or author contact attempts.