Purpose:
To determine if developmental patterns of change in corneal astigmatism differ in astigmatic and non-astigmatic infants who are members of a Native American Tribe with a high prevalence of corneal astigmatism.
Methods:
Subjects were Tohono O’odham children participating in a longitudinal study of refractive error development. The present analysis included the 52 children who were recruited into the study prior to age 1 year, and for whom we had data at all three of the youngest ages (6 months to < 1 year, 1 to < 2 years, 2 to < 3 years). Measurements of corneal astigmatism were obtained with the IK4 video keratoscope. Repeated measures ANOVAs were used to compare change in corneal astigmatism (clinical notation, J0, and J45) over time between children classified as astigmatic (≥2D corneal astigmatism) and non-astigmatic (<2D corneal astigmatism) at their baseline (< age 1 year) assessment.
Results:
Corneal astigmatism (clinical notation) analyses yielded a significant main effect of age (p < 0.05) and a significant interaction between age and amount of baseline corneal astigmatism (p < 0.004). Astigmatism decreased after infancy in the high astigmatism group (p=0.021) and then remained relatively stable with a modest decrease from age 2 to 3 years (NS). Astigmatism was stable from infancy to 1 year in the low-astigmatism group (NS), with an increase from age 2 to age 3 years (p=0.026). Analyses of J0 yielded a similar pattern of results. Analysis of J45 yielded no significant effects.
Conclusions:
A previously observed reduction in prevalence of corneal astigmatism in Tohono O’odham 1 year olds, observed in cross-sectional data, was due to difference in developmental patterns for astigmatic and non-astigmatic infants. From infancy to age 2 years, astigmatic infants showed a a significant decrease in astigmatism (average 0.9D), as reported in other populations of infants. Non-astigmatic infants tended to a small increase in astigmatism through age 2 years (0.2 D).
Keywords: visual development • astigmatism • clinical research methodology