PURPOSE
This investigation studied the factors involved in the development of refractive error (RE) in premature infants unaffected by retinopathy of prematurity (ROP).
METHODS
Premature infants enrolled in the national ROP screening program were recruited and examined at 32, 36, 40, 44, and 52 weeks' postmenstrual age. At each examination, axial length (AXL), anterior chamber depth (ACD), and lens thickness (LT) were measured on the A-scan biometer. Corneal curvature (CC) was recorded with a video-ophthalmophakometer, and refractive state was determined with routine cycloplegic refraction. Multilevel modeling techniques were used to determine the relationships between all the variables throughout the study period, as well as individual growth rates.
RESULTS
Sixty-eight premature infants were included. AXL and ACD showed linear patterns of growth, whereas LT changed little over the study period. CC showed a quadratic growth pattern, and unlike the previous variables, correlated well with refractive state. Premature infants were myopes at the start of the study, with refraction becoming emmetropic as they neared full term and then hypermetropic toward the end of the study.
CONCLUSIONS
Most of the components of refractive status showed linear patterns of growth during this early phase of ocular development. CC displayed a more complex pattern of growth, which correlated well with refractive state. Compared with full-term infants examined around term, this group has shorter AXLs, shallower anterior chambers, and more highly curved corneas. In addition, less of the expected hypermetropia developed in the premature group, which seems mainly due to the differences in ACD and corneal curvature.