Abstract
Purpose:
Children with infantile esotropia (IET) often fail to emmetropize during the first year of life (Birch et al. Eye, 2010). Nonetheless, after 5-6 years of persistent moderate hyperopia, many children with IET experience a myopic shift of -0.50D/yr when they are 7-12 years old (Birch et al Eye, 2010). Because eye shape and peripheral retinal defocus are thought to play an important role in controlling myopic progression, we examined foveal and peripheral biometric and refractive data associated with the early hyperopia and later myopic shift in 3- to 14-year-old children with IET.
Methods:
Eye length (right eye) was measured with a Haag-Streit Lenstar in 40 children with infantile ET. Five measurements were obtained at the fovea and at 10° and 20° on the temporal retina. For off-axis measurements, children fixated a dim mini-LED affixed to the instrument. Distance refraction (right eye) was obtained for the same 3 locations with a Grand Seiko binocular autorefractor with the child fixating letter targets.
Results:
At 3-4 and 5-6 years old, children with IET had mean±se refractive error of +3.63±0.61D and +3.81±0.43D, respectively, and axial length of 21.4±0.3mm and 21.2±0.2mm, respectively. Peripheral eye length was 0.2-0.4 mm longer than axial length, consistent with oblate ocular shape. Peripheral refraction was -0.84 to -0.91D more myopic relative to foveal refraction. At 7-8 years, mean hyperopia was lower (+2.66±0.67D) and axial length longer (22.1±0.2mm). In this age group, peripheral eye length was shorter than axial length by 0.1-0.3 mm; i.e., eyes were less oblate in shape. By 9-14 years, mean hyperopia was again lower at +1.54±0.76D and axial length longer at 23.1±0.5mm; eyes were even less oblate (peripheral eye length was 0.2-0.4 mm shorter than axial length). In the older age groups peripheral refraction remained slightly myopic (-0.1 to -0.2D) relative to foveal refraction.
Conclusions:
Hyperopia in IET is associated with oblate eye shape. While the putative “stop” signal of relative peripheral myopia is present in younger eyes, the older eyes are significantly longer and significantly less oblate at 7-14 years of age, just as the children experience a myopic shift. The possibility that some eyes can grow rapidly to become less hyperopic despite inhibitory peripheral defocus requires longitudinal confirmation.
Keywords: 511 emmetropization •
677 refractive error development •
722 strabismus