June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Antagonistic effects of atropine and timolol on the color and luminance emmetropization mechanisms
Author Affiliations & Notes
  • Laura Ann Goldberg
    New England College of Optometry, Boston, MA
  • Frances J Rucker
    New England College of Optometry, Boston, MA
  • Footnotes
    Commercial Relationships Laura Goldberg, None; Frances Rucker, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 2150. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to Subscribers Only
      Sign In or Create an Account ×
    • Get Citation

      Laura Ann Goldberg, Frances J Rucker; Antagonistic effects of atropine and timolol on the color and luminance emmetropization mechanisms. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2150.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract

Purpose: The role of the autonomic nervous system in the color and luminance emmetropization mechanisms is unknown. This study analyzed the response to the non-selective, parasympathetic antagonist, atropine, and the sympatholytic, beta-adrenergic antagonist, timolol, in chicks subjected to illumination conditions that selectively stimulate the color and luminance emmetropization mechanisms.

Methods: Chicks were binocularly exposed eight hours each day, for four days, to one of three illumination conditions: 2Hz sinusoidal luminance flicker (LUM), 2Hz sinusoidal color flicker (B/Y), or steady light. Mean illuminance was 680 lux. Eyes received daily injections of either 20μl atropine (18nmol) (N=8), 2 drops of 0.5% timolol (N=8), 20μl phosphate-buffered saline (N=8), or no injection (N=8). Measurements of the axial dimensions of ocular components and refraction were performed using A-scan ultrasonography, photorefraction and a Hardinger Refractometer. In each illumination condition, the saline effect was subtracted from the drug effect [Drug (ΔX-ΔN) - Saline (ΔX-ΔN)].

Results: LUM flicker demonstrated opposite effects on eye growth and refraction with atropine and timolol treatment. Atropine caused a reduction in eye growth (-0.08 ± 0.02 mm, p=0.01) and a reduction in vitreous chamber depth (-0.10 ± 0.02 mm, p=0.004), evoking a hyperopic shift in refraction (3.40 ± 1.77 D), despite an antagonistic increase in lens thickness (0.14 ± 0.05 mm, p=0.004). In contrast, timolol elicited a myopic shift in refraction (-4.07 ± 0.92 D, p=0.001), due to an increase in eye length (0.045 ± 0.030 mm). Color flicker induced choroidal compensation for eye growth, preventing refractive shifts with atropine and timolol. With atropine, hyperopia was not observed, because a reduction in eye length (-0.05 ± 0.02 mm, p=0.01) was compensated for by choroidal thinning (-0.05 ± 0.02 mm, p=0.03). With timolol, myopia did not occur because a reduction in eye length (-0.05 ± 0.018 mm, p=0.02) was also compensated for by choroidal thinning (-0.052 ± 0.015 mm, p=0.01).

Conclusions: The opposing growth and refractive effects of atropine and timolol with luminance flicker, and the compensatory choroidal compensation with color flicker, suggest a precise balancing mechanism between the parasympathetic and sympathetic nervous system, and the visual environment, in achieving emmetropization.

×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×