Pediatric IOL Calculation

Abstract

The minimal age limit at which intraocular lens (IOL) implantation should be used in children remains controversial. What is clear is that the younger the surgery is performed, the more unpredictable are the subsequent shifts in refractive error over time.1Mezer E. Rootman D.S. Abdolell M. Levin A.V. Early postoperative refractive outcomes of pediatric intraocular lens implantation.J Cataract Refract Surg. 2004; 30: 603-610Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar, 2Nihalani B. VanderVeen D.K. Comparison of intraocular lens power calculation formulae in pediatric eyes.Ophthalmology. 2010; 117: 1493-1499Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar Various formulae designed for adult eyes, are used to calculate the IOL optical power needed to obtain the target postoperative refraction. These formulas have shown varying degrees of accuracy in the eyes of children. Other challenges to accurate IOL power calculation include the shorter pediatric eye with steeper corneas. Measurements performed under anesthesia may be more inaccurate due to uncertain “fixation.” In addition, refraction has to be done manually by retinoscopy rather than with an automated refractometer. We previously published a series of 59 eyes, which were mostly in the lower range of size for normal adult eyes.1Mezer E. Rootman D.S. Abdolell M. Levin A.V. Early postoperative refractive outcomes of pediatric intraocular lens implantation.J Cataract Refract Surg. 2004; 30: 603-610Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar The Hoffer Q formula resulted in better accuracy of prediction but the difference was not statistically significant than other newer theoretical formulas (Holladay 1and SRK/T).3Retzlaff J.A. Sanders D.R. Kraff M.C. Development of the SRK/T intraocular lens implant power calculation formula.J Cataract Refract Surg. 1990; 16: 333-340Abstract Full Text PDF PubMed Scopus (709) Google Scholar In contrast, the older regression formulas (SRK, SRKII) were statistically significantly less accurate. Nihalani and VanderVeen2Nihalani B. VanderVeen D.K. Comparison of intraocular lens power calculation formulae in pediatric eyes.Ophthalmology. 2010; 117: 1493-1499Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar examined 135 eyes of which 69 were shorter than average. This enabled them to perform subgroup analysis, which was not possible in our previous study due to the small sample size. They showed a trend toward greater prediction error (PE) in eyes of children younger than 2 years, in shorter eyes and steeper corneas. As in our study, Hoffer Q performed better than the other formulas, especially in younger children and in short eyes. No statistical significance was reported in this study. Perhaps the major difference between their work and ours was the follow-up length: up to 2 months in their paper and up to 6 months in ours. A significant deviation from predicted refraction of more than 0.5 diopter (D) was noted in the Nihalani study in almost 60% of the cases with a tendency for all formulas towards undercorrection. The PE range utilizing Hoffer Q was 1.86 D after a follow-up of 1 to 2 months. Our study shows that this trend continues using all formulas with a deviation from predicted refraction of 1.1 D on average (range to 3.03 D) 2-3 months after surgery using Hoffer Q. The PE in our study further increased after 2 to 6 months of follow-up, again with the Hoffer Q formula, and reached an average of 1.37 D (range of 7.4 D). In conclusion, our ability to hit the target refraction for pediatric IOL implantation is still imperfect. This is especially true for younger children or those with shorter eyes. We join Nihalani and VanderVeen in suggesting that until further refinement of IOL power calculation for pediatric eyes is achieved, surgeons, and parents should be aware of the inherent variation in prediction of the refractive outcome. Comparison of Intraocular Lens Power Calculation Formulae in Pediatric EyesOphthalmologyVol. 117Issue 8PreviewTo evaluate accuracy of intraocular lens (IOL) power calculation formulae (SRK II, SRK/T, Holladay 1, Hoffer Q) in pediatric eyes. Full-Text PDF Author replyOphthalmologyVol. 118Issue 6PreviewWe would like to thank Dr. Mezer and Dr. Levin for their interest in our article1 and for bringing out interesting comparison points between their previously published study2 and our recent study. The aim of our study was to evaluate accuracy of intraocular lens (IOL) power calculation formulae; hence, we only included the first postoperative refraction obtained between 4 to 8 weeks after surgery. We did not evaluate refractive changes over time as these may be influenced by the myopic shift, which is higher in younger children. Full-Text PDF