Opposing effects of atropine and timolol on the color and luminance emmetropization mechanisms in chicks

作者：Goldberg Laura A^*; Rucker Frances J

来源：Vision Research, 2016, 122: 1-11.

DOI：10.1016/j.visres.2016.03.001

• Emmetropization
• Myopia
• Atropine
• Timolol
• Luminance
• Color

This study analyzed the luminance and color emmetropization response in chicks treated with the nonselective parasympathetic antagonist atropine and the sympathetic beta-receptor blocker timolol.
Chicks were binocularly exposed (8 h/day) for 4 days to one of three illumination conditions: 2 Hz sinusoidal luminance flicker, 2 Hz sinusoidal blue/yellow color flicker, or steady light (mean 680 lux). Atropine experiments involved monocular daily injections of either 20 mu l of atropine (18 nmol) or 20 mu l of phosphate-buffered saline. Timolol experiments involved monocular daily applications of 2 drops of 0.5% timolol or 2 drops of distilled H2O. Changes in the experimental eye were compared with those in the fellow eye after correction for the effects of saline/water treatments.
Atropine caused a reduction in axial length with both luminance flicker (-0.078 +/- 0.021 mm) and color flicker (-0.054 +/- 0.017 mm), and a reduction in vitreous chamber depth with luminance flicker (-0.095 +/- 0.023 mm), evoking a hyperopic shift in refraction (3.40 +/- 1.77 D). Timolol produced an increase in axial length with luminance flicker (0.045 +/- 0.030 mm) and a myopic shift in refraction (-4.07 +/- 0.92 D), while color flicker caused a significant decrease in axial length (-0.046 +/- 0.017 mm) that was associated with choroidal thinning (-0.046 +/- 0.015 mm).
The opposing effects on growth and refraction seen with atropine and timolol suggest a balancing mechanism between the parasympathetic and beta-receptor mediated sympathetic system through stimulation of the retina with luminance and color contrast.

• 出版日期2016-5