Advisability of primary intraocular lens implantation for infants under 2: A systematic review and meta-analysis

Author: Jin S, Zhang J, Wang J, Yusufu M, Cao K, Zhu G, He H, Wan XH.

Geographical coverage: Not reported

Sector: Cataract treatment

Sub-sector: Intraocular lens implantation

Equity focus: Not reported

Study population: Paediatric patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Globally, childhood blindness affects approximately 1.4 million children, with paediatric cataracts accounting for 5%–20% of these cases. Two primary surgical approaches are used to manage paediatric cataracts: primary intraocular lens (IOL) implantation, where the lens is implanted immediately after cataract extraction, and primary aphakia, where the eye remains lens-free and visual correction is provided with contact lenses or spectacles. However, concerns about postoperative complications, such as inflammatory responses, visual axis opacification (VAO), and secondary glaucoma, have made the optimal surgical strategy controversial. Evidence on visual outcomes and complications remains inconsistent, especially in infants under two years of age. The incidence of glaucoma appears comparable between the two approaches, though consensus is lacking.

Objective: To compare the postoperative visual performance of primary IOL implantation and primary aphakia in infants with cataract younger than 2 years old, so as to provide solid evidence for better clinical practice.

Main findings: The review included 8 studies (3 randomised controlled trials [RCTs] and 5 retrospective studies), published between 2001 and 2018. These eight studies were reported in 11 publications, with 4 publications reporting the data from the same RCT (The Infant Aphakia Treatment Study, IATS trial). The surgery age of subjects ranged from 1.8 to 7.5 months, and the follow-up duration ranged from 0.7 to 5 years. The included studies compared the outcomes of primary intraocular lens (IOL) implantation versus primary aphakia with optical correction in infants under two years of age with congenital cataracts.

In terms of visual acuity, children in the primary IOL group showed significantly better outcomes than those in the aphakia group. Specifically, among children younger than 4.5 years, the mean difference in VA favoured the IOL group (MD = −0.14, 95% confidence interval [CI]: −0.23 to −0.06), with similar trends observed in RCT-only (odds ratio, OR = −0.12, 95% CI: −0.20, −0.04, P = 0.56) and unilateral surgery (OR = −0.14, 95% CI: −0.22 to −0.06, P =0.87) subgroups. These results suggest that primary IOL implantation may accelerate early visual rehabilitation in this population. Regarding glaucoma, there was no statistically significant difference in incidence between the two groups (OR = 1.02, 95% CI: 0.62 to 1.68, P = 0.48), and no heterogeneity was observed across studies. Subgroup analyses confirmed this finding.  For strabismus, results were mixed. The RCT subgroup showed no significant difference (OR = 1.59, 95% CI: 0.83 to 3.05, P = 0.82), but retrospective studies indicated a lower incidence in the IOL group (OR = 0.33, 95% CI: 0.13 to 0.85, P = 0.33). These divergent findings likely reflect variation in study quality and follow-up rigour, particularly between real-world and trial settings. Similarly, nystagmus and retinal detachment showed no significant differences between groups (nystagmus: OR = 1.26, 95% CI: 0.68 to 2.36, P = 0.92; retinal detachment: OR = 0.49, 95% CI: 0.07 to 3.30, P = 0.34), and heterogeneity across studies remained low for both outcomes. However, the incidence of VAO, requiring surgical clearing, was significantly higher in the primary IOL group (OR = 9.22, 95% CI: 4.74 to 17.96, P = 0.16).

Overall, the results suggest that while primary IOL implantation offers superior visual outcomes, it also carries a higher risk of VAO and no clear advantage in reducing other complications such as glaucoma.

Methodology:  The searches were conducted in PubMed, Embase, Science Direct and Cochrane Library between 1 January 2000 to 2 August 2020. Studies were included if they involved infants under two years of age who underwent cataract extraction, either with primary intraocular lens (IOL) implantation or without lens implantation (aphakia), with correction provided by contact lenses or spectacles. The studies were included if they included a follow-up period of at least six months, were published in English, and reported data per operated eye rather than per patient.

Two reviewers independently screened the articles and extracted the relevant data. Disagreements between the reviewers were resolved through discussion or by contacting a third reviewer. The quality of the included studies was assessed using the Newcastle–Ottawa Scale for cohort studies and the Cochrane risk of bias tool for randomised controlled trials. The findings were synthesised using a fixed-effects model when heterogeneity was low (I² < 50%) and a random-effects model when heterogeneity was high (I² ≥ 50%), with heterogeneity assessed using the Cochrane Q test and I² statistics. Publication bias is assessed using an Egger asymmetry test. Sensitivity analysis was also performed to determine whether the heterogeneity would decrease following the exclusion of each study one by one. Subgroup analysis and meta-regression were performed according to the clinical characteristics of the included studies.

Applicability/external validity: The review did not explicitly discuss the external validity or generalisability of its findings in detail. However, it acknowledged certain limitations that may impact applicability, such as the inclusion of both RCTs and retrospective studies, variability in diagnostic criteria (particularly for glaucoma), and challenges in replicating intensive follow-up protocols like those used in the IATS trial. These factors suggest that while the findings offer valuable insights, their translation into real-world clinical settings should be approached with caution.

Geographic focus: The review did not apply any geographical limits. However, it did not report the geographical distribution of the included studies.

Summary of quality assessment: Overall, there is medium confidence in the review’s conclusions. The searches were comprehensive. Inclusion and exclusion criteria were clearly defined, and two reviewers independently screened the articles, extracted data and assessed the study quality using established tools, with disagreements resolved through discussion or consultation with a third reviewer. Characteristics of included studies were well-documented, meta-analyses were appropriately performed, and heterogeneity was addressed. However, the search was limited to identifying articles published in the English language only. The review did not provide a list of excluded studies, nor did it report checking the reference lists of the included studies.