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Viral Sheth, Irene Gottlob, Frank A Proudlock; Investigating the relationship between foveal hypoplasia and refractive error in infantile nystagmus. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4417.
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© ARVO (1962-2015); The Authors (2016-present)
Infantile nystagmus (IN) and its associated conditions, such as albinism, are often associated with refractive errors. Form deprivation myopia (FDM) can be caused by factors such as foveal hypoplasia or retinal motion. In contrast, other factors, such as hyper-illumination of the eye in albinism, due to reduced pigmentation in the iris, may lead to hyperopia. In this study we investigated the relationship between refractive error and axial length with foveal hypoplasia and iris thinning in four phenotypically different IN groups (albinism, idiopathic IN, PAX6 mutations and achromatopsia).
Refractive error, macular optical coherence tomography (OCT) and best-corrected visual acuity was measured in 72 individuals with IN (albinism=33, idiopathic IN=18, PAX6 mutation=9 and achromatopsia=12). Foveal hypoplasia was graded subjectively using a foveal hypoplasia grading scheme from OCT images (grades 0-4) and measured objectively using a foveal development index (FDI = thickness of inner foveal layers / total foveal thickness). Thickness of the iris posterior epithelial layer was measured in albinism participants using anterior segment OCT.
Increased myopia was associated with greater foveal hypoplasia (measured using FDI) in achromatopsia (P<0.05). In contrast, no significant correlations were found for the PAX6 or idiopathic IN groups. For albinism participants, low grades of foveal hypoplasia and better visual acuity were associated with myopia and longer axial lengths, whereas high grades of foveal hypoplasia and poor visual acuity were associated with hyperopia and shorter axial lengths (P<0.05). In albinism, hyperopia and shorter axial lengths were also associated with significant iris posterior epithelial layer thinning (P<0.01).
The origin of refractive errors in infantile nystagmus appear disease specific. Form deprivation, caused by foveal hypoplasia, is likely to explain the myopic trend seen in achromatopsia and in mild forms of albinism. In more severe forms of albinism, however, the trend of increasing hyperopia is probably explained by hyper-illumination of the eye (because of iris transillumination), rather than foveal hypoplasia, dominating the pattern of refractive error. In albinism, refractive error was strongly associated with changes in axial length.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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