Purpose:
To determine the prevalence of high refractive astigmatism in Native American (Tohono O’odham) children age 6 months to 8 years.
Methods:
Children were recruited through Women, Infants and Children (WIC) clinics, the Head Start Program, and K and 1st grade elementary school classrooms on the Tohono O’odham Reservation from September 2005 to November 2007. Three right eye (RE) non-cycloplegic SureSight (ncSS, Welch Allyn) autorefraction measurements were attempted on all children, and the median cylinder was used to estimate amount of astigmatism present. In addition, for children age 3 years and older, gold standard estimates of RE astigmatism (cRmax, cycloplegic autorefraction (Nikon Retinomax)) were also obtained to assess the accuracy of ncSS measurements.
Results:
Measurements were attempted on 956 children; no ncSS estimate could be obtained on 9 children due to poor cooperation. Analyses of data from children 3 and older (n=486) indicated that ncSS tended to overestimate astigmatism, compared to cRmax measurement (cRmax = -0.06 + 0.63 * ncSS, R2=0.69), and that in 95% of ncSS "out of range" measurements, cRmax indicated that astigmatism ≥ 2.00D was present. The regression equation was applied to median ncSS measurements for all subjects, and RE astigmatism was estimated based on this corrected ncSS estimate. More children < 1 year old had ≥ 1.00D of astigmatism compared to older age groups (70% vs < 55% in all older age groups, all ps< 0.05 before Bonferroni correction, all ps except < 1 year vs. 2 to < 3 years and 5 to < 6 years < 0.05 after correction). More < 1 year olds than 1 to <4 year olds, and more 5-6 year olds than 1 to <3 year olds had ≥ 2.00D of astigmatism (ps < 0.05 before Bonferroni correction, not significant after correction).
Conclusions:
Results are consistent with reports from other populations that suggest that high astigmatism is more prevalent during the first year of life than in subsequent years. However, as reported with data from older children from this population, the overall prevalence of astigmatism is greater than the prevalence observed in other non-Native American populations.
Keywords: astigmatism • clinical (human) or epidemiologic studies: prevalence/incidence • development