Accuracy Of Intraocular Lens Power Calculation In Pediatric Cataract Surgery

ObjectiveCataract is a major cause of blindness in children throughout the world, particularly in developing countries. Because of its potential for inhibiting and restricting early visual development. Early surgery now is universally accepted for younger age children with cataract, and the placement of an intraocular lens in children and infants undergoing lens aspiration is gaining wider acceptance. Axial elongation and changes in corneal curvature are major factors influencing refractive changes in the early childhood life. Because of the complexity of the functions of the eye and the numerous factors involved in its refraction, the calculation of the IOL power is somewhat complicated. In our study, SRKⅡwas used to calculate the degree of IOL, and check the refractive status by retinoscopy. To determine the accuracy of intraocular lens (IOL) power calculation in pseudophakic children.MethodsA retrospective analysis of biometric and refractive data was performed on 62 eyes of 37 infants and children, aged from 1.6 to 6.8 years, on a averge of 2.9±1.3 years. All the children need to take surgery. Children with glaucoma before and after surgery were excluded from this study.10% chloral hydrate were given oral or enema per 1 ml/kg before the measurement.A-scan was used to measure the axial length, and SRKⅡwas used to calculate the IOL power. The postoperative refractive outcome was taken as the spherical equivalent of the refraction at 2 months after surgery by retinoscopy. The data were analyzed to assess the effects of age at the time of surgery, axial length, and primary or secondary intraocular lens implantation on the accuracy of calculation of IOL power.Results1. In this study,62 eyes were included, the length of axis from 17.74mm to 26.27mm, on a average of 21.12±1.68mm. The axis length increases gradually with age. Besides, all the children with axis length<20 mm were younger than 2 years.2. For the overall group the mean and median prediction errors were 1.56D (SD 1.43). There were 32 eyes'absolute prediction errors lower than ID (52%). The mean absolute prediction errors in eyes with axial lengths<20 mm were 2.75 D (SD1.66), and in eyes>20 mm were 1.06 D (SD 0.93). The mean absolute prediction errors in eyes in children aged≤2 years were2.38 D (SD 1.65), and in children aged>2 years were 1.04D (SD 0.99). The differences between the absolute prediction errors for both axial length and age were statistically significant (P<0.01). The mean absolute prediction errors in eyes with primary IOL implantation were 1.37D(SD 1.35), and secondary intraocular lens implantation were 2.03D(SD 1.56). The differences between the absolute prediction errors primary or secondary intraocular lens implantation, were not statistically significant (P=0.22).Conclusions1.For the overall group IOL power calculation is generally acceptable. In eyes with axial lengths less than 20 mm and in children younger than 2 years of age larger errors can arise, and the variations increase.2. An IOL formula specifically designed for pediatric use is needed.