Accuracy of intraocular lens power calculation in paediatric cataract surgery

Aims - To determine the accuracy of intraocular lens (IOL) power calculation in a group of pseudophakic children. Methods - A retrospective analysis of biometric and refractive data was performed on 52 eyes of 40 infants and children, who successfully underwent cataract extraction and IOL implantation. The following parameters were included: age at the time of surgery, keratometry, axial length, estimated refraction, and the power of IOL implanted. The postoperative refractive outcome was taken as the spherical equivalent of the refraction at 3 months after surgery. The prediction error was taken as the absolute difference between the estimated and actual postoperative refraction. The data were analysed to assess the effects of age at the time of surgery, keratometry, and axial length on the accuracy of calculation of IOL power. Results - For the overall group the mean and median prediction errors were 1.40 D and 0.84 D (SD 1.60). The mean and median prediction errors in eyes with axial lengths greater than or equal to 20 mm were 1.07 D and 0.71 D (SD 0.98) and in eyes < 20 mm. were 2.63 D and 2.61 D (SD 2.65). The mean and median prediction errors in eyes in children aged greater than or equal to 36 months were 1.06 D and 0.68 D (SD 1.02) and in children aged < 36 months was 2.56 D and 2.29 D (SD 2.50). The differences between the prediction errors for both axial length and age were statistically significant (p <0.05). Conclusions - For the overall group IOL, power calculation is satisfactory. In eyes with axial lengths less than 20 mm. and in children less than 36 months of age larger errors can arise. This study demonstrates the need for an IOL formula specifically designed for paediatric use.