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J. Felius, D.R. Stager, Sr., D.R. Weakley, J.N. Leffler, E.E. Birch; Convergence–Accommodation Relationships in Children at Risk for Accommodative Esotropia . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2488.
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© ARVO (1962-2015); The Authors (2016-present)
Hypermetropia, anisometropia, and a history of infantile esotropia are known risk factors for the development of accommodative esotropia at the age of 2–4 years. The disease mechanism is poorly understood, especially for children who were earlier successfully treated for infantile esotropia. It has been suggested that these children may have abnormalities in the link between convergence and accommodation (C/A link). We evaluated the C/A link among patients, risk groups and normal children.
The 'response C/A ratio' (RC/A) was determined under free–viewing conditions across a 1–4 D demand using a combined infrared photorefractor and gaze tracker (PowerRefractor) in 26 children (age 2.7 + 1.8 years) with one or more known risk factors: >3 D hypermetropia, >2 D anisometropia, history of infantile esotropia; 22 children with accommodative esotropia (age 3.2 + 1.2 years; 7 post infantile esotropia, 15 late–onset); and 25 normal controls (age 2.9 + 1.1 years).
Mean RC/A in the control group was 0.62 meter–angle/D (95%–c.i., 0.24–1.00). Abnormally high RC/A was found in 15% of children at risk and 27% of patients with accommodative esotropia. In the children at risk, abnormal RC/A correlated strongly with history of infantile esotropia (P=0.008; Fisher's exact test) and somewhat with anisometropia (P=0.05). In patients with accommodative esotropia, the prevalence of abnormal RC/A in those with a history of infantile esotropia (3/7) was not statistically different from that in patients with late–onset accommodative esotropia (3/15; P=0.3). No associations were found between RC/A and the presence of amblyopia or the absence of stereopsis in any of the patient groups.
These findings support the hypothesis that abnormalities in the C/A link are an underlying factor in the disease mechanism for accommodative esotropia in patients with infantile esotropia after surgical realignment. It remains to be investigated whether such abnormalities are induced by the surgery, or pre–existing but masked clinically by a large non–accommodative component of the preoperative misalignment.
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