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J. Wang, L. M. Wyatt, J. Felius, D. R. Stager, Jr., D. R. Stager, Sr., E. E. Birch, H. E. Bedell; With-The-Rule Astigmatism in Children With Infantile Nystagmus Syndrome During the First Four Years of Life. Invest. Ophthalmol. Vis. Sci. 2008;49(13):143.
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Previous reports indicate that adults with nystagmus frequently have with-the-rule (WTR) astigmatism. Whether WTR astigmatism develops as a consequence of nystagmus interfering with emmetropization is unknown. The aim of this study is to examine the development of refractive error, especially WTR astigmatism, during the first 4 years of life in children with idiopathic Infantile Nystagmus Syndrome (INS) and INS associated with albinism, and to compare their development with normal children (Mayer et al, 2001).
Cycloplegic refractions culled from medical records were converted into power vector components: M (spherical equivalent), J0 (positive J0 indicates WTR astigmatism) and J45 (oblique astigmatism) (Thibos, et al, 1997). Each diagnostic group (idiopathic: n=57; albinism: n=99; normal: 495) was divided into younger (<1 year old) and older (1-4 year old) sub-groups.
WTR astigmatism ≥1D was prevalent among children with INS even during infancy (among subjects <1 year, idiopathic: 22%; albinism: 46%) but not among normal infants (8%; p<0.05). In this age group, J0 was significantly higher in children with INS than in normals (idiopathic INS: 0.18±0.32; INS with albinism: 0.42±0.52; normal: -0.07±0.16; p<0.001). Both the prevalence and magnitude of WTR astigmatism increased with age in the Idiopathic and Albinism groups but not in normals. Moreover, whereas normal children showed evidence of emmetropization over this age range (M decreased by 0.72D between the younger and older age groups), children with Idiopathic INS demonstrated little change in M (mean: -0.10D) and children with Albinism showed a significant trend away from emmetropia (M increased by 0.72D between the younger and older age groups).
WTR astigmatism in INS has been proposed to result from mechanical distortion of the cornea and/or from motion-induced blur. The high prevalence of WTR astigmatism in infants with INS suggests either that these forces interfere with emmetropization during the first year of life or that WTR astigmatism is congenital. Infantile abnormalities in refractive development are followed by failure to emmetropize over the next 3 years. The poorer visual acuity of the Albinism group may exacerbate abnormalities in refractive development.
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