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Juvenile Tree Shrews Do Not Maintain Emmetropia in Narrow-band Blue Light.
Gawne, Timothy J; Ward, Alexander H; Norton, Thomas T.
Afiliação
  • Ward AH; Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, Alabama *tgawne@gmail.com.
  • Norton TT; Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, Alabama *tgawne@gmail.com.
Optom Vis Sci ; 95(10): 911-920, 2018 10.
Article em En | MEDLINE | ID: mdl-30179995
SIGNIFICANCE: In spectrally broad-band light, an emmetropization mechanism in post-natal eyes uses visual cues to modulate the growth of the eye to achieve and maintain near emmetropia. When we restricted available wavelengths to narrow-band blue light, juvenile tree shrews (diurnal dichromatic mammals closely related to primates) developed substantial refractive errors, suggesting that feedback from defocus-related changes in the relative activation of long- and short-wavelength-sensitive cones is essential to maintain emmetropia. PURPOSE: The purpose of this study was to examine the effects of narrow-band ambient blue light on refractive state in juvenile tree shrews that had completed initial emmetropization (decrease from hyperopia toward emmetropia). METHODS: Animals were raised in fluorescent colony lighting until they began blue-light treatment at 24 days of visual experience, at which age they had achieved age-normal low hyperopia (mean ± SEM refractive error, 1.2 ± 0.5 diopters). Arrays of light-emitting diodes placed atop the cage produced wavelengths of 457 (five animals) or 464 nm (five animals), flickered in a pseudo-random pattern (temporally broad band). A third group of five animals was exposed to steady 464-nm blue light. Illuminance on the floor of the cage was 300 to 500 human lux. Noncycloplegic autorefractor measures were made daily for a minimum of 11 days and up to 32 days. Seven age-matched animals were raised in colony light. RESULTS: The refractive state of all blue-treated animals moved outside the 95% confidence limits of the colony-light animals' refractions. Most refractions first moved toward hyperopia. Then the refractive state decreased monotonically and, in some animals, passed through emmetropia, becoming myopic. CONCLUSIONS: From the tree shrew cone absorbance spectra, the narrow-band blue light stimulated both long-wavelength-sensitive and short-wavelength-sensitive cones, but the relative activation would not change with the refractive state. This removed feedback from longitudinal chromatic aberration that may be essential to maintain emmetropia.
Assuntos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Tupaiidae / Emetropia / Luz Limite: Animals Idioma: En Ano de publicação: 2018 Tipo de documento: Article

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Tupaiidae / Emetropia / Luz Limite: Animals Idioma: En Ano de publicação: 2018 Tipo de documento: Article