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A. M. Cottrell, L. Levine; The Accuracy of Pediatric Intraocular Lens Calculations Using the SRK II Formula. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4830.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the the accuracy of the SRK II formula in pediatric cataract surgery at our institution, and identify methods to improve refractive outcomes in pediatric patients. Current data indicates that a wide range of predictive error is possible regardless of which formula is used.
The measured outcome is the absolute difference between the predicted and the actual postoperative spherical equivalent (prediction error). The strength of this association is measured by the Pearson correlation coefficient. All measurements and surgeries were performed by one surgeon from 1998-present and include patients ages 1-15 (n=21).
The SRK II formula tends to predict a more hyperopic spherical equivalent with a Pearson correlation coefficient of 0.73 (p = 0.0001). The mean prediction error is 1.14D. There is no significant correlation between prediction error and axial length (-0.057, p = 0.806), or between patients under and over age 5 (prediction error 1.35 vs. 1.01, p = 0.40)
According to the major published studies to date, no formula demonstrates accuracy in children comparable to that seen in adults. Our data shows that the SRK II formula provides predictable postoperative outcomes, and the prediction error is not solely dependent on axial length or age alone. There are multiple factors leading to prediction error in children, including a smaller anterior chamber depth and a larger lens relative to intraocular volume. The use of the SRK II formula at our institution is justified based on low overall prediction error. Refractive outcomes can be improved for many patients by adjusting intraocular lens power to account for this hyperopic prediction error.
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