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Amy Davis, John Daniel Twelker, Joseph M Miller, Erin M Harvey; The Relation Between Convergence Insufficiency and Astigmatism. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):532.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if children with moderate/high astigmatism have an increased rate of convergence insufficiency compared to children with no/low astigmatism.
Subjects were 3rd-8th grade Tohono O’odham students who have a high prevalence of astigmatism. An eye examination including subjective refinement of Retinomax (Nikon, Inc.) cycloplegic autorefraction was performed on each student. Spectacle correction was prescribed for students with a significant refractive error (>1D myopia, >1D astigmatism, >2.5D hyperopia, >1.5D anisometropia). Hyperopic correction was reduced by 1/3 or by 1.00D whichever was greater. Cover testing at distance and near, near point of convergence, positive and negative fusional vergence at near (fusional convergence and divergence amplitudes), accommodative amplitude (Donder’s pushup method), and symptoms (Convergence Insufficiency Symptom Survey (CISS)) testing was conducted while students wore spectacle correction (if prescribed). Students with an exodeviation at near at least 4∆ greater than at far, a receded NPC (6 cm or greater), and insufficient positive fusional vergence at near (PFV) (convergence amplitudes) (i.e., failing Sheard’s criterion (PFV less than twice the near phoria) or minimum PFV of < 15∆ base-out blur or break), and a CISS score of > 16 were classified as having convergence insufficiency. Astigmatism was categorized by magnitude in the most astigmatic eye (<1D, 1 to <3D, ≥3D). Chi-square analysis was conducted to determine the relation between convergence insufficiency and astigmatism magnitude.
The final sample included 484 Tohono Oodham students ages 8.26 to 15.87 years. Prevalence of convergence insufficiency was 6.2% (30/484). Astigmatism <1.00D was present in 43.8% (212/484), >1D to <3D was present in 26.0% (126/484) and > 3D was present in 30.2% (146/484). There was no significant relation between presence of convergence insufficiency and magnitude of astigmatism (p=0.30, see Table and Graph).
The prevalence of convergence insufficiency is consistent with reports from other samples, although this finding should be interpreted with caution as the present sample was not population-based. The results suggest that children with moderate to high astigmatism are not at an increased risk for convergence insufficiency.
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