June 1996
Volume 37, Issue 7
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Articles  |   June 1996
The M1 muscarinic antagonist pirenzepine reduces myopia and eye enlargement in the tree shrew.
Author Affiliations
  • C L Cottriall
    Department of Optometry and Vision Sciences, University of Wales, Cardiff, United Kingdom.
  • N A McBrien
    Department of Optometry and Vision Sciences, University of Wales, Cardiff, United Kingdom.
Investigative Ophthalmology & Visual Science June 1996, Vol.37, 1368-1379. doi:
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      C L Cottriall, N A McBrien; The M1 muscarinic antagonist pirenzepine reduces myopia and eye enlargement in the tree shrew.. Invest. Ophthalmol. Vis. Sci. 1996;37(7):1368-1379.

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Abstract

PURPOSE: To determine the efficacy of the M1-selective muscarinic antagonist, pirenzepine, in preventing experimentally induced myopia in a mammalian model, the tree shrew. METHODS: Tree shrews were monocularly deprived (MD) using translucent goggles or negative lenses for a period of 12 days. In two of the MD groups, tree shrews received daily subconjunctival administration of either pirenzepine (17.7 mumol; n = 9) or vehicle control (n = 6). Control groups (n = 6) were used to assess the effects of MD, injection regimen, and drug effects. RESULTS: In sham-injected and saline-injected MD tree shrews, 12 days of MD produced-13.2 D +/- 0.8 D and -14.1 D +/- 0.5 D of axial myopia, respectively. In pirenzepine-injected MD tree shrews, 12 days of MD induced an axial myopia of only -2.1 D +/- 1.4 D. The significant reduction in myopia in pirenzepine-injected MD tree shrews was caused by significantly less vitreous chamber elongation of the deprived eye (0.05 mm +/- 0.04 mm) relative to the contralateral control eye when compared to sham-injected and saline-injected MD tree shrews (0.24 mm +/- 0.02 mm and 0.29 mm +/- 0.01 mm). Mean equatorial enlargement and increased eye weight were prevented in pirenzepine-injected MD tree shrews (P < 0.01). Pirenzepine also was found to reduce myopia and ocular enlargement in lens defocus-induced myopia. Control experiments demonstrated that pirenzepine did not cause a significant reduction in amplitude of carbachol-induced accommodation. CONCLUSIONS: Findings demonstrate that chronic administration of the M1-selective muscarinic antagonist, pirenzepine, prevents experimentally induced myopia in this mammalian model by a nonaccommodative mechanism.

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