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Updated: Jul 23, 2026
The Measurement and Treatment of Suppression in Amblyopia
Published on: December 14, 2012
Astigmatism and Amblyopia among Native American Children (AANAC): design and methods
J M Miller1, V M Dobson, E M Harvey
1Department of Ophthalmology, University of Arizona, Tucson, Arizona, United States of America. jmiller@eyes.arizona.edu
Insights
This study evaluated four astigmatism screening tools for preschool children, aiming to prevent amblyopia. Early correction with glasses showed benefits in improving visual acuity and preventing vision impairment.
Area of Science:
- Ophthalmology
- Public Health
- Pediatrics
Background:
- Astigmatism and amblyopia are prevalent in certain populations, necessitating effective early detection strategies.
- Preschool-aged children are a critical group for vision screening to prevent long-term visual impairment.
- The Tohono O'Odham Nation has a high prevalence of astigmatism, making it an ideal population for this study.
Purpose of the Study:
- To evaluate the effectiveness of four screening methods for astigmatism in preschool children.
- To assess the short-term and long-term benefits of early astigmatism correction on visual acuity and amblyopia prevention.
- To determine the sensitivity and specificity of different screening tools for detecting significant astigmatism.
Main Methods:
- Four screening tools (autokeratometer, photoscreener, autorefractor, acuity chart) were used on preschool children.
- Cycloplegic retinoscopy and autorefraction served as the gold standard for astigmatism measurement.
- Children with significant astigmatism received corrective spectacles, with visual outcomes monitored.
Main Results:
- The study determined the sensitivity and specificity of each of the four screening tools for astigmatism detection.
- Effectiveness of early intervention was assessed by monitoring visual acuity and amblyopia persistence after spectacle wear.
- Long-term visual acuity was compared between children who received the screening and those who did not.
Conclusions:
- Early detection and correction of astigmatism in preschool children can improve visual acuity.
- Effective screening tools are crucial for preventing amblyopia and its long-term consequences.
- This research provides valuable data on the efficacy of vision screening programs in high-prevalence populations.
Abstract:
The overall goal of the AANAC study is to improve detection of astigmatism and prevention of amblyopia in populations with a high prevalence of astigmatism. To meet this goal, the study will evaluate four methods of screening for astigmatism in preschool children and will assess both the short-term and long-term benefits of early correction of astigmatism in improving acuity and preventing amblyopia. This paper presents an overview of the design and methodology of the AANAC study. Subjects are members of the Tohono O'Odham Nation, a Native American tribe with a high prevalence of astigmatism. Preschool-age children who attend Head Start are screened with four tools: the Marco Nidek KM-500 autokeratometer, the MTI photoscreener, the Nikon Retinomax K-Plus autorefractor, and the Lea Symbols acuity chart. Sensitivity and specificity for detection of significant astigmatism, as measured by a technique that uses both cycloplegic retinoscopy and cycloplegic autorefraction, is determined for each of the four screening tools. Presence of amblyopia is evaluated by measurement of best-corrected recognition acuity and acuity for orthogonal gratings. Spectacles are provided to all 3-year-old children with > or =2.00 diopters (D) of astigmatism and all 4- and 5-year-old children with > or =1.50 D of astigmatism. Persistence of amblyopia after glasses wearing is evaluated by follow-up measurement of best-corrected recognition acuity and acuity for orthogonal gratings, conducted 2-5 months after glasses are prescribed. Long-term effectiveness of early screening and glasses prescription is evaluated through measurement of recognition acuity in two groups of first-grade children: one group who participated in the Head Start program before the intensive vision screening program was initiated, and a second group who participated in the study's Head Start vision screening program.
