Ocular growth and refractive error development in premature infants with or without retinopathy of prematurity

To study factors involved in the development of refractive error in premature infants with or without retinopathy of prematurity (ROP).

Premature infants in the national ROP screening program were recruited and examined longitudinally between 32 and 52 weeks' postmenstrual age. Axial length (AL), anterior chamber depth (ACD), and lens thickness (LT) were measured on the A-scan biometer. Corneal curvature was recorded with video-ophthalmophakometry and refractive state was determined with routine cycloplegic retinoscopy. Multilevel modeling techniques were used to study relationships between all the variables and stage of ROP throughout the study period, as well as individual growth rates.

One hundred thirty-six infants were included. AL and ACD showed linear patterns of growth, whereas LT changed little over the study. Corneal curvature showed quadratic growth patterns in infants unaffected by ROP, but showed linear growth if ROP developed. Corneal curvature correlated well with refractive state. Most infants were myopic at the start of the study, became emmetropic around term, and were hypermetropic toward the end of the study. However, the eyes that were treated for ROP showed little change in refractive error; with significantly less hypermetropia by the end of the study.

Eyes of premature infants have shorter axial lengths, shallower anterior chambers, and more highly curved corneas than eyes of full-term infants. These differences become more significant as the severity of ROP increases. Premature eyes develop less of the expected hypermetropia in full-term eyes, mainly due to differences in ACD and corneal curvature. These differences are most significant in eyes that receive laser treatment for ROP.