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Zachary Vest, Serena Wang; The accuracy of intraocular lens formulas in children ages 2 to 18 at Children’s Medical Center of Dallas. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6716.
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The goal of this study is to evaluate four common IOL formulas (Holladay, Hoffer Q, SRK/T, SRK II) when applied to eyes implanted with one-piece intra-capsular IOLs in pediatric patients over 2 years old at one institution with all cases and measurements performed by one surgeon.
A retrospective case review of all intraocular cases performed by one surgeon (S.W.) at Children’s Medical Center of Dallas over a 3 year period (1/2008-12/2012) were collected. Cases of cataract extraction with primary placement of a one-piece intraocular lens were included. Any case with anterior or posterior segment abnormality or lack of follow up was excluded. All eyes had intra-operative axial length and keratometry measurements. Cycloplegic refractions were recorded at 4-8 weeks post-operatively and converted to spherical equivalent. The predicted refraction for all four formulas was then calculated.The prediction error (PE) and the absolute PE (the absolute value of PE) were calculated. Prediction error is defined as:Prediction error (PE) = predicted refraction- actual refractionThe mean absolute PE for each formula was then compared using a paired t-test. A significant PE was defined as +/- 0.5 D. Correlation was then calculated for each of the 4 formulas.
153 cases of congenital, acquired and traumatic cataract were identified from the retrospective chart review. After exclusion criterion 51 eyes were included in the study. Six cases were bilateral. All cases involved a one piece acrylic lens (SN60AT or SA60AT) placed into the capsular bag.The average age was 8.1 years with a range from 2-18 years. There was no statistically significant difference in the mean PE between the four formulas. The percentage of eyes without significant predictive error was 43%, 41%, 39% and 29% for Hoffer Q, Holladay 1, SRK/T and SRK II respectively. All four formulas provided similar correlations to the real refractive outcome. All four equations provided a mean PE that was statistically different from the real refractive outcome according to paired t-testing.
The results of this study correlates with prior findings that current IOL formulas and data collection techniques need to be improved for the pediatric population. Patients older than 2 years old have less variable refractive outcomes than younger patients but there is still need for improved refractive outcomes. All four formulas performed comparably in this age group. Further improvement in data collection (AL collection, keratometry) and refinement of IOL formulas specifically for the pediatric eye are needed to further improve overall refractive outcomes in the pediatric population.
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