Congenital and infantile cataracts represent a leading, avoidable cause of childhood visual impairment and amblyopia in low- and middle-income countries (LMICs), with Pakistan bearing a disproportionate share of this burden [1, 2]. The overarching principle governing the management of paediatric cataract is the restoration of a clear optical axis at the earliest possible opportunity, thereby permitting unobstructed visual stimulation during the sensitive period of visual cortical development — a window that is at its most sensitive within the first 6 to 10 weeks of postnatal life and progressively diminishes in plasticity thereafter [3]. Failure to achieve this is invariably accompanied by profound and often irreversible amblyopia, with lifelong implications for functional vision, educational attainment, and quality of life.

The question of whether optical rehabilitation following cataract extraction should be achieved through primary intraocular lens (IOL) implantation or through aphakic spectacle or contact lens correction remains one of the most debated topics in paediatric ophthalmology. The landmark Infant Aphakia Treatment Study (IATS) — a multicentre randomised controlled trial conducted in the United States — demonstrated that primary IOL implantation in infants under seven months of age did not confer superior visual acuity outcomes compared to contact lens correction at age 4.5 years, and was associated with a substantially higher rate of post-operative adverse events, particularly secondary glaucoma and the need for additional ocular surgical interventions [3, 4]. However, the generalisability of these findings to the Pakistani clinical context requires careful and critical re-evaluation, given the profound disparities in healthcare access, contact lens affordability, caregiver literacy, and rehabilitation infrastructure.

In Peshawar and the broader Khyber Pakhtunkhwa (KPK) region, contact lens correction of aphakia presents formidable practical challenges. The cost of daily silicone hydrogel contact lenses for infants, the technical difficulty of lens insertion and removal by caregivers with limited formal education, the absence of a reliable supply chain for paediatric contact lenses outside major urban centres, and the high risk of lens loss in resource-constrained household environments collectively make contact lens-based aphakic rehabilitation impracticable for a large proportion of the patient population [5, 6]. These contextual realities drive paediatric ophthalmic surgeons in Peshawar toward primary IOL implantation at earlier ages than Western practice guidelines advocate, necessitating a rigorous, locally contextualised assessment of the safety implications of this practice.

The safety profile of IOL implantation in the infant eye is fundamentally distinct from that in older children and adults, owing to the anatomical and physiological characteristics of the immature globe. The infant eye continues to undergo significant axial growth (emmetropisation) throughout the first decade of life, rendering any fixed-power IOL subject to progressive, predictable myopic shift as the globe elongates [7, 8]. The degree of target undercorrection required to account for anticipated myopic shift — the so-called 'leave hyperopic' strategy — must be individualised based on the child's age at implantation and projected axial growth, a calculation that introduces an additional layer of complexity absent in adult IOL selection [8].

Posterior capsule opacification (PCO) constitutes the most frequent post-operative complication of paediatric cataract surgery and occurs at far higher rates in infants than in older patients, attributable to the markedly greater proliferative capacity of the residual lens epithelial cells in the immature eye [9, 10]. Secondary glaucoma is the most vision-threatening long-term complication, occurring in up to 20-31% of paediatric cataract surgery cases across published series, with an incidence that is higher in eyes implanted at younger ages, in eyes with unilateral cataract, and in eyes that experienced intraoperative vitreous loss [9, 10]. Given that post-operative glaucoma may be clinically silent in infants — presenting with minimal symptoms until advanced structural optic nerve damage has occurred — its early detection is critically dependent on structured, regular intraocular pressure monitoring, a protocol that is difficult to sustain in settings with limited follow-up compliance.

Published data from Pakistani centres, including a study from Lahore by Ejaz et al. [11] and a preliminary series from HMC Peshawar by Imran et al. [12], have begun to document the complication profile of paediatric IOL implantation in the local context, reporting PCO rates of 28-36% and glaucoma incidence of 10-18%. However, these studies are limited by relatively small sample sizes, short follow-up durations, and incomplete characterisation of predictors of specific complications. The epidemiological profile of paediatric cataract in KPK — marked by a higher prevalence of consanguinity-related hereditary disease, delayed presentation, and limited follow-up adherence — demands a dedicated, adequately powered study from Peshawar.

Against this background, the present study was designed to provide a comprehensive safety evaluation of primary IOL implantation in children under two years of age at leading tertiary eye care institutions in Peshawar, with the specific aims of: (i) characterising the full spectrum of intraoperative and post-operative complications; (ii) identifying clinical and surgical predictors of secondary glaucoma, PCO, and IOL decentration; (iii) documenting long-term visual acuity and refractive outcomes stratified by age at implantation; and (iv) informing the development of evidence-based, context-specific clinical protocols for paediatric IOL implantation in KPK

2.1 Study Design This study employed a retrospective cohort design to systematically evaluate the safety profile of primary IOL implantation in children aged 0 to 24 months. Retrospective COHORT methodology was selected to enable the evaluation of a sufficiently large cohort with adequate follow-up duration within a defined and feasible data collection timeframe, while permitting comprehensive documentation of the full spectrum of complications that may evolve over the course of postoperative follow-up. 2.2 Study Settings The study was conducted at tertiary ophthalmology referral centres in Peshawar: Hayatabad Medical Complex (HMC) . This centre serve as a principal referral destinations for paediatric eye disease across KPK and Federally Administered Tribal Areas (FATA), managing a large, diverse, and predominantly socioeconomically disadvantaged patient population. The institute has dedicated paediatric ophthalmology units with consultant paediatric ophthalmologists, trained paediatric anaesthetists, and post-operative rehabilitation services. 2.3 Study Duration Surgical and follow-up records were reviewed for all eligible patients who underwent primary IOL implantation between January 2024 and May 2025. 2.4 Sampling Technique and Sample Size Calculation Non-probability consecutive sampling was employed, wherein all paediatric patients who met the predefined eligibility criteria were enrolled from the surgical registers of HMC. This technique is the most pragmatic and widely adopted approach in clinical studies at Pakistani tertiary hospitals, providing adequate representation of the patient population while minimising procedural bias [6]. Sample size was calculated using the Raosoft® online sample size calculator (www.raosoft.com/samplesize.html), the most widely cited sample size determination tool in Pakistani biomedical research publications [12]. Based on a reported incidence of clinically significant post-operative complications (PCO and/or glaucoma) of approximately 35% in comparable South Asian paediatric cataract surgery series [11], a margin of error of 5%, and a 95% confidence level, the minimum calculated sample size was 111 patients. Adjusting for an anticipated 12% incomplete record rate, the target enrolment was set at 125 patients. 2.5 Inclusion and Exclusion Criteria Inclusion criteria: • Children aged 0 to 24 months at the time of primary IOL implantation for congenital or infantile cataract at HMC , Peshawar. • Primary IOL implantation performed as part of the index cataract surgery (not secondary implantation into a previously aphakic eye). • Availability of complete operative notes and post-operative follow-up records. • Informed consent (retrospective) provided by parent or legal guardian for inclusion of clinical data in the study. Exclusion criteria: • Children with traumatic cataract, or cataract secondary to complex systemic syndromes (e.g., Lowe syndrome, Nance-Horan syndrome, Rubinstein-Taybi syndrome) with confounding ocular pathology. • Eyes with concurrent structural anomalies (microphthalmos, persistent foetal vasculature, aniridia, anterior segment dysgenesis) independently predisposing to glaucoma or optical rehabilitation failure. • Secondary IOL implantation in previously aphakic eyes. • Incomplete surgical or post-operative records precluding adequate safety assessment. 2.6 Data Collection Procedure Standardised data extraction was performed by two trained research officers using a pre-piloted, structured data extraction proforma. Variables collected included: patient demographics (age, sex, residential district, parental educational attainment, estimated household income); surgical details (age at IOL implantation, laterality, IOL material and design, IOL power and target refraction, surgical technique — in-the-bag vs. sulcus fixation, performance of primary posterior capsulectomy and anterior vitrectomy, intraoperative complications); post-operative management (optical correction modality, amblyopia therapy prescribed and compliance, follow-up frequency); and outcome data (best-corrected visual acuity at most recent review, manifest refraction, post-operative complications identified, intraocular pressure measurements, and any additional surgical interventions performed). Visual acuity was assessed using age-appropriate methods. Fixation behavior (central, steady, maintained) was evaluated in preverbal infants, Cardiff Acuity Cards or Lea Symbols were used for cooperative preschool children, and Snellen or logMAR visual acuity charts were used for older cooperative children whenever feasible. Best-corrected visual acuity (BCVA) recorded at the latest available postoperative follow-up was included for analysis. 2.7 Statistical Analysis All data were entered into Microsoft Excel 2019 and statistical analysis was performed using IBM SPSS Statistics version 22.0 (IBM Corp., Armonk, NY, USA). Continuous variables were expressed as mean ± standard deviation (SD), whereas categorical variables were presented as frequencies and percentages. Associations between categorical variables were assessed using the Chi-square test or Fisher’s exact test where appropriate and the independent samples t-test or one-way ANOVA for continuous variables.. Univariate logistic regression analysis was performed to identify factors associated with postoperative complications. A p-value <0.05 was considered statistically significant. Odds ratios (ORs) with 95% confidence intervals (CIs) are reported throughout. Statistical significance was defined as a two-tailed p-value of < 0.05. 2.8 Ethical Considerations Ethical approval for this study was granted by the Institutional Review Boards of Hayatabad Medical Complex Peshawar. The study was conducted in accordance with the principles of the Declaration of Helsinki (2013 revision) and Good Clinical Practice guidelines. Patient anonymity was preserved through the use of coded identifiers throughout data extraction, analysis, and reporting.

3.1 Demographic and Clinical Characteristics

A total of 125 children were enrolled, comprising 59 males (47.2%) and 66 females (52.8%). The mean age at primary IOL implantation was 9.6 ± 6.1 months (range: 3 weeks to 23 months). Unilateral cataract accounted for 56.8% (n=71) of cases, while 43.2% (n=54) had bilateral disease. Hydrophilic acrylic IOLs were the most frequently implanted lens material (59.2%), followed by PMMA (27.2%) and hydrophobic acrylic (13.6%). Full demographic and clinical characteristics are presented in Table 1.

Table 1: Demographic and Clinical Characteristics of Study Participants (n=125)

Note: IOL = Intraocular Lens; PMMA = Polymethylmethacrylate; SE = Spherical Equivalent; D = Dioptre; SD = Standard Deviation

3.2 Intraoperative Complications

Intraoperative complications were documented in 23 patients (18.4%). Posterior capsule rupture was the most frequent intraoperative event, occurring in 9 eyes (7.2%), all of which were managed with anterior vitrectomy, with IOL placement in the ciliary sulcus in seven cases. Vitreous prolapse occurred in 6 eyes (4.8%), zonular dialysis in 4 eyes (3.2%), and corneal wound leakage requiring resuturing in 3 eyes (2.4%). One patient (0.8%) experienced an intraoperative suprachoroidal haemorrhage that was managed conservatively. The distribution of intraoperative complications and their management is presented in Table 2.

Table 2: Intraoperative Complications and Management (n=125)

Note: CTR = Capsular Tension Ring; IOL = Intraocular Lens

3.3 Post-operative Complications

Post-operative complications were recorded in 91 patients (72.8% of the cohort) over the follow-up period. Posterior capsule opacification (PCO) was the most prevalent complication, occurring in 43 patients (34.4%). Refractory amblyopia despite documented compliance with prescribed patching or atropine penalization therapy was observed in 26 patients (20.8%). Clinically significant secondary glaucoma (intraocular pressure >21 mmHg on two or more separate recordings, with or without structural optic nerve changes) was confirmed in 19 patients (15.2%), of whom 11 required surgical intervention (goniotomy, trabeculectomy, or glaucoma drainage device implantation). IOL decentration or displacement was documented in 14 patients (11.2%), necessitating surgical repositioning in 8 cases. The complete post-operative complication profile is presented in Table 3.

Table 3: Post-operative Complications and Their Management (n=125)

Note: PCO = Posterior Capsule Opacification; IOP = Intraocular Pressure; DSAEK = Descemet's Stripping Automated Endothelial Keratoplasty

3.4 Visual Acuity Outcomes by Age at Implantation

Visual acuity outcomes were significantly superior in patients implanted at younger ages. Children who received IOL implantation before 6 months of age achieved good visual acuity (6/6-6/12) in 57.9% of cases, compared to 53.8% in the 6-12 month group and 37.1% in the > 12 month group (p=0.002 and p=0.018 respectively compared to the oldest group). The mean logMAR BCVA at most recent follow-up was best in the youngest implantation age group (0.28 ± 0.21) and worst in the oldest group (0.48 ± 0.30). Detailed visual acuity outcomes stratified by age at implantation are presented in Table 4.

Table 4: Best-Corrected Visual Acuity Outcomes Stratified by Age at IOL Implantation

Note: VA = Visual Acuity; logMAR = Logarithm of the Minimum Angle of Resolution; SD = Standard Deviation; p-values calculated vs. 12-24 months reference group using chi-square test

3.5 Predictors of Secondary Glaucoma

Univariate logistic regression identified age at implantation below 6 months, intraoperative posterior capsule rupture, persistent post-operative uveitis, and unilateral cataract as statistically significant predictors of secondary glaucoma. Age at implantation below 6 months carried the highest risk (OR 3.82; 95% CI 1.74-8.38; p<0.001), followed by intraoperative posterior capsule rupture (OR 4.61; 95% CI 1.53-13.89; p=0.007) and persistent post-operative uveitis (OR 3.44; 95% CI 1.42-8.31; p=0.006). PMMA IOL material and prior intraocular surgery approached but did not reach statistical significance. These findings are detailed in Table 5.

Table 5: Univariate Logistic Regression: Predictors of Secondary Glaucoma (n=125)

Note: OR = Odds Ratio; CI = Confidence Interval; IOP = Intraocular Pressure; PMMA = Polymethylmethacrylate

3.6 Refractive Outcomes

Refractive outcomes demonstrated a progressive myopic shift across all age groups during the follow-up period, consistent with the anticipated pattern of ocular emmetropisation in the growing infant eye. Overall, 59.2% of patients achieved a final refraction within ±1D of the surgical target. A myopic shift of 1-3D from the intended target was documented in 20.8% of patients, while 12.0% demonstrated a shift exceeding 3D, predominantly in the youngest implantation age group. The mean spherical equivalent change from target across the entire cohort was -1.5 ± 1.2D. Refractive outcomes stratified by age at implantation are presented in Table 6.

Table 6: Refractive Outcomes Stratified by Age at IOL Implantation (n=125)

Note: SE = Spherical Equivalent; D = Dioptre; SD = Standard Deviation; Values represent shift from surgical target refraction

The present study provides a comprehensive, locally contextualised safety evaluation of primary IOL implantation in children under two years of age in Peshawar, KPK — a clinical practice that is widespread in the region despite being approached with caution in high-income country settings. The overall complication rate documented in this cohort (72.8% of patients experiencing at least one post-operative complication) — while reflecting the inherent complexity of surgery in the immature eye — is broadly consistent with rates reported in comparable South Asian and LMIC settings, including a 68.4% combined complication rate reported by Ejaz et al. from Lahore [11] and a 51.7% rate in the series from LRH Peshawar by M. iqbal et al. [12]. These rates substantially exceed those reported in the IATS (approximately 48% in the IOL arm) [3], likely reflecting differences in patient selection criteria, IOL material diversity, surgical technique variation, and the quality and frequency of post-operative monitoring available in the Pakistani setting. The PCO rate of 34.4% documented in this study reflects the biological reality of the infant lens epithelium's vigorous regenerative capacity and aligns closely with previously published rates from regional series. Wilson ME et al. documented PCO rates of 29-38% in infants undergoing IOL implantation, with rates inversely related to the completeness of primary posterior capsulectomy and anterior vitrectomy performed at the index surgery [8]. A critical observation from the present cohort is that primary posterior capsulectomy was not uniformly performed at index surgery — a variation in surgical technique that likely accounts for a significant proportion of PCO cases. Standardisation of primary posterior capsulectomy with anterior vitrectomy as a mandatory intraoperative step for all IOL implantations in children under 8 years of age is strongly supported by the existing evidence base and should be adopted as a protocol at paediatric cataract surgery centres across KPK. The secondary glaucoma rate of 15.2% is particularly concerning given the silent and progressive nature of intraocular pressure elevation in infants. This rate is intermediate between rates reported in Western series (8-31% across published long-term studies) [9, 10] and underscores the importance of lifelong intraocular pressure monitoring in all eyes that have undergone paediatric cataract surgery. The identification of age at implantation below 6 months as the strongest predictor of secondary glaucoma (OR 3.82; p<0.001) replicates the findings of Lambert et al. [10] and of the IATS, and has direct practical implications: clinicians in Peshawar who elect to implant IOLs in very young infants must ensure that an explicit protocol for frequent, regular intraocular pressure measurement is established and that caregivers are educated regarding the signs of raised IOP, including photophobia, epiphora, and buphthalmos. The superior visual acuity outcomes achieved in children implanted before 6 months of age (good VA in 57.9%) compared with those implanted at 12-24 months (37.1%) affirm the critical importance of early optical rehabilitation and align with the broader neuroscientific evidence regarding sensitive period visual cortical plasticity [4]. These findings highlight a fundamental tension in the management of paediatric cataract in the KPK context: earlier surgery is associated with the best visual outcomes but the highest complication risk, particularly glaucoma. Resolution of this tension demands a nuanced, individualised surgical decision-making framework that considers the patient's specific clinical and social circumstances — including family capacity for contact lens management, geographic accessibility to follow-up, and household socioeconomic resources — rather than a blanket policy of either universal IOL implantation or universal primary aphakia. The high rate of IOL decentration (11.2%) documented in this cohort likely reflects a combination of factors including in-the-bag IOL placement in eyes with potentially compromised capsular support, intraoperative zonular weakness, and the use of PMMA lenses — which carry a greater decentration risk than one-piece acrylic designs — in 27.2% of cases [7]. Adoption of a standardised surgical protocol favouring in-the-bag placement of single-piece hydrophilic or hydrophobic acrylic IOLs, with capsular tension ring insertion in eyes with suspected zonular laxity, would be expected to reduce the decentration rate in future surgical cohorts. The progressive myopic shift observed across all age groups — with a mean spherical equivalent change of -1.5 ± 1.2D from target — underscores the unpredictability of refractive outcomes following infant IOL implantation and the critical role of regular, structured refraction and optical rehabilitation in maximising functional visual outcomes over the growing years. Mirza Mahbubur Rahman et al. have previously documented the challenges of follow-up compliance among paediatric ophthalmology patients in Bangladesh [6], and the present data reinforce the urgency of implementing community health worker-facilitated outreach, SMS-based appointment reminder systems, and subsidised transport for follow-up visits as structural interventions to improve post-operative surveillance adherence in this population.

This study from Peshawar, Khyber Pakhtunkhwa, demonstrates that primary IOL implantation in children under two years of age is associated with a substantial and clinically significant burden of intraoperative and post-operative complications, of which posterior capsule opacification (34.4%) and secondary glaucoma (15.2%) are the most prevalent and clinically consequential. Earlier age at implantation is associated with superior long-term visual acuity outcomes but carries a paradoxically elevated risk of secondary glaucoma, creating a nuanced risk-benefit calculus that must be individualised for each patient and family within the specific socioeconomic and healthcare access context of KPK.

The findings of this study have several urgent practical implications for paediatric cataract surgery practice in Peshawar and KPK. First, the universal adoption of primary posterior capsulectomy with anterior vitrectomy at the index surgical procedure for all children under eight years of age is strongly recommended as a protocol-level intervention to reduce PCO burden. Second, a structured, lifelong intraocular pressure monitoring protocol — commencing at the earliest post-operative visit and continuing at every subsequent review — should be implemented for all eyes that have undergone paediatric cataract surgery with IOL implantation. Third, the decision to implant a primary IOL in an infant under six months of age should be made in the context of a multidisciplinary discussion that carefully weighs the visual rehabilitation advantages against the elevated glaucoma risk, with explicit informed consent from the family. Fourth, caregiver education programmes — developed in Pashto and Urdu, delivered in culturally sensitive formats, and incorporating community health worker engagement — are essential to improve compliance with post-operative follow-up, optical rehabilitation, and amblyopia therapy.

Prospective longitudinal multicentre studies across KPK, incorporating standardised surgical protocols, quality-of-life assessment instruments validated for the Pakistani paediatric context, and long-term refractive outcome data extending to school age and beyond, are strongly recommended to build upon these foundational findings and to establish a provincial evidence base for paediatric cataract surgery practice standards.

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