Predictability of Intraocular Lens Power Calculation Formulae in Infantile Eyes With Unilateral Congenital Cataract: Results from the Infant Aphakia Treatment Study

Abstract

PURPOSE To compare accuracy of intraocular lens (IOL) power calculation formulae in infantile eyes with primary IOL implantation. DESIGN Comparative case series. METHODS The Hoffer Q, Holladay 1, Holladay 2, Sanders-Retzlaff-Kraff (SRK) II, and Sanders-Retzlaff-Kraff theoretic (SRK/T) formulae were used to calculate predicted postoperative refraction for eyes that received primary IOL implantation in the Infant Aphakia Treatment Study. The protocol targeted postoperative hyperopia of +6.0 or +8.0 diopters (D). Eyes were excluded for invalid biometry, lack of refractive data at the specified postoperative visit, diagnosis of glaucoma or suspected glaucoma, or sulcus IOL placement. Actual refraction 1 month after surgery was converted to spherical equivalent and prediction error (predicted refraction – actual refraction) was calculated. Baseline characteristics were analyzed for effect on prediction error for each formula. The main outcome measure was absolute prediction error. RESULTS Forty-three eyes were studied; mean axial length was 18.1 ± 1.1 mm (in 23 eyes, it was <18.0 mm). Average age at surgery was 2.5 ± 1.5 months. Holladay 1 showed the lowest median absolute prediction error (1.2 D); a paired comparison of medians showed clinically similar results using the Holladay 1 and SRK/T formulae (median difference, 0.3 D). Comparison of the mean absolute prediction error showed the lowest values using the SRK/T formula (1.4 ± 1.1 D), followed by the Holladay 1 formula (1.7 ± 1.3 D). Calculations with an optimized constant showed the lowest values and no significant difference between the Holladay 1 and SRK/T formulae (median difference, 0.3 D). Eyes with globe AL of less than 18 mm had the largest mean and median prediction error and absolute prediction error, regardless of the formula used. CONCLUSIONS The Holladay 1 and SRK/T formulae gave equally good results and had the best predictive value for infant eyes.

Comparison of IOL power calculation formulae for pediatric eyes

“…Andreo et al 4 reported that there was minimal difference between SRK/T, SRK II, Holladay 1, and Hoffer Q formulae in terms of their predictive accuracy in short, medium, and long eyes. Vanderveen et al 12 reported results from 43 eyes of infants, with a mean age of 2.5 months and ALo20 mm in most eyes. In this prospective, randomized multicenter trial, they reported that both SRK/T and Holladay 1 formulae worked equally well in terms of median prediction errors.…”

“…Further, they also reported that age, AL, and K values did not influence predictive accuracy, except for the Holladay and Hoffer Q formulae that were influenced by AL. On the other hand, several authors 5,12 reported that a shorter AL had a significant bearing on the predictive accuracy of the IOL calculation formula. Although mean PE tells us about the direction of miscalculation, the APE is a useful measure to compare overall predictive accuracy of the different formulae.…”

“…In adult eyes, formulae that may have an advantage in terms of accuracy based on AL are: ALo22 mm: Hoffer Q, Holladay 2; AL 22-26 mm: Holladay I, Hoffer Q, SRK/T; AL426 mm: SRK/T, Holladay 2. 12 In pediatric eyes, however, results are inconsistent. [4][5][6][7][8][10][11][12] Further, most published studies in the literature are retrospective.…”

“…12 In pediatric eyes, however, results are inconsistent. [4][5][6][7][8][10][11][12] Further, most published studies in the literature are retrospective. [4][5][6][7][8]10,11 Optimizing or personalizing the lens constant has been recommended by authors of several formulae to improve their accuracy and predictability.…”

“…[4][5][6][7][8][9] Further, several authors have compared the accuracy of different IOL formulae designed for adult eyes in predicting early postoperative refractive error in eyes of infants and young children. 7,[9][10][11][12] However, there is no consensus as to which formula provides the best prediction of early postoperative refraction, particularly in the extremely small eye. In adult eyes, formulae that may have an advantage in terms of accuracy based on AL are: ALo22 mm: Hoffer Q, Holladay 2; AL 22-26 mm: Holladay I, Hoffer Q, SRK/T; AL426 mm: SRK/T, Holladay 2.…”