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E Eugenie Hartmann, Michael Lynn, Scott Lambert, Infant Aphakia Treatment Study; Timing matters: Relationship between age at initial surgery and monocular grating acuity at 12 months in the Infant Aphakia Treatment Study (IATS). Invest. Ophthalmol. Vis. Sci. 2013;54(15):5985.
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To evaluate the impact of patient age at surgery on monocular grating visual acuity in the treated eye for infants enrolled in IATS.
IATS is a multi-center, randomized clinical trial for the treatment of unilateral congenital cataracts in infants between 1 and <7 months of age. 114 patients were enrolled in the study between 2004 and 2009. Infants were randomly assigned to either contact lens (CL) treatment or initial implantation of an IOL after cataract surgery. Randomization of infants was stratified between two age groups: 28-41 days and 42-208 days to ensure that equal numbers of younger infants were treated with each intervention. Monocular grating visual acuity was estimated at 12 months of age (+ 2 months) by a traveling vision tester using the Teller Acuity Cards. We found no significant difference in the median logMAR grating acuity between the two treatment groups (CL: 0.80; IOL: 0.97; p=.19). A critical consideration in the treatment of congenital cataracts is the timing of surgery. Given that monocular grating acuity at 12 months was not significantly different between the treatment groups we evaluated the effect of age at surgery and grating acuity at 12 months of age in the treated eye for all 114 infants as one group.
Grating visual acuity (VA) in the treated eye ranged from 2.79 to 0.49 logMAR. The correlation between VA and age at surgery, shown in Figure 1, was not significant (Spearman Rank Correlation=0.15; p=0.11). Based on evidence that binocular functioning (e.g., stereopsis) is not generally present in human infants until 12-13 weeks of age, we chose to compare VA in infants who had had surgery <91 days with those whose surgery had been performed later. Median VA was 0.80 logMAR for <91 days at surgery and 0.97 logMAR for >91 days at surgery. A Wilcoxon Rank Sum Test yielded a significant difference (p=0.03). (See Figure 2.)
Our data illustrate that good grating VA measured at 12 months may be obtained in infants whose surgery is performed anytime between 28 and 208 days. We suggest that the optimal period for surgery is limited by the interval before the non-cataractous eye begins to dominate neural connections in the visual cortex and may extend up to approximately 91 days.
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