Paediatric Cataract Surgery As Refractive Surgery: Accuracy Of Srk/T Formula And Postoperative Refractive Error Prediction In Paediatric Cataract Surgery

Paediatric cataract is commonest avoidable cause of childhood visual disability but even with successful cataract surgery, desired optical outcome may not be achieved. Only 66% of paediatric eyes attain 1.00 D of SE of target refraction vs 97.8% in adults. Paediatric eyes undergo myopic shift, have shorter Axial Length, steeper corneal curvature, higher K value and shallower ACD and ELP may be affected by the need for an anterior vitrectomy. To avoid anisometropic amblyopia and myopic shift, accurate prediction of postoperative refraction is imperative. We investigated the accuracy of IOL power calculation using SRK/T formula and postoperative refractive error prediction in paediatric population.

This is prospective consecutive case-series conducted at Children Eye Hospital (ASTEH), Rawalpindi (the only Children eye-hospital in Pakistan). All patients aged 6 months to 8 years who underwent uneventful cataract surgery and in-the-bag IOL implantation with biometry using SRK/T formula between Mar,2025 to Oct,2025 were included. Patients with aphakia, secondary IOL Implantation, other ocular disorders like PHPV, glaucoma, uveitis, microcornea or having previous ocular surgery were excluded.

All patients underwent Visual Acuity examination using Snellen chart, Cardiff cards, toys. Autokeratorefractometry, biomicroscopy and indirect fundoscopy exam, contact A-scan and biometry was performed with or without sedation. Demographic data included age, sex, and laterality. Biometry data included, AL, K and A constant and IOL power. For analysis eyes were divided into subgroups based on AL; very short <20.00mm short 20.00 - 22.00mm, moderate 22.01mm – 24.49 and long 24.5- 26.00mm, very long >26.00mm. Hyperopia was aimed by implanted IOL power to be 80% of calculated IOL power for ages < 2 years and 90% for ages 2-8 years. Refractive error was measured by streak retinoscopy and converted to SE. Prediction error was then calculated.

A total of 351 eyes were included, with 138 Female and 213 Male, age ranged from 6months to 8 years and axial length ranged from 17.20 to 31.44mm. The mean predicted refractive error was 3.54 ± 1.87 D. Accuracy improved with increasing axial length. A paired t-test showed a statistically significant difference between predicted and actual refractive error (t(350)=16.24, p<0.001). Similarly, the Wilcoxon signed-rank test confirmed a significant difference (p<0.001). Regarding accuracy, 31.3% of eyes were within ±0.5 D, 44.4% within ±1.0 D, and 67.5% within ±2.0 D of the predicted refractive outcome. 

In paediatric population the main factor decreasing the likelihood of amblyopia and better visual outcome is the accuracy of predicted postoperative refractive error, The formula’s performance is not uniform across ages and axial lengths.Age is clearly an important covariate. Axial length also plays a role. Longer axial length is associated with more myopic refractive error. In very short eyes, prediction error increased by approximately 0.62 D per 1 mm increase in axial length suggesting a trend toward relatively less myopic (more hyperopic) outcomes. Further studies are required for Paediatric IOL Calculation formula and development of standard model for aiming hyperopia and adjustment for higher myopic shift in asian eyes.