Atropine reduces experimental myopia and eye enlargement via a nonaccommodative mechanism.

TLDR

The study aimed to test whether atropine can reduce or prevent experimentally induced myopia through a nonaccommodative mechanism. The experiment involved monocularly deprived chicks receiving intravitreal atropine or saline injections, with control groups to evaluate the effects of deprivation and injection. Atropine markedly reduced experimental myopia and axial elongation without affecting accommodation or pupil constriction, indicating a nonaccommodative mechanism.

Abstract

To determine whether the muscarinic antagonist atropine effectively reduces or prevents experimentally induced myopia via a nonaccommodative mechanism.Chicks were monocularly deprived (MD) of pattern vision by placement of a translucent occluder over the left eye. In two of the three MD groups, chicks received a series of intravitreal injections of atropine (n = 8) or saline vehicle (n = 8) with MD. Control groups (n = 8) of chicks were employed to assess the effects of MD, intravitreal injections, and drug effects.In sham-injected or saline-injected MD chicks, 8 days of MD produced -18.5 D and -20.9 D of experimental myopia, respectively. In atropine-injected MD chicks, 8 days of MD produced only -2.8 D of experimental myopia. This significant reduction in experimentally induced myopia in atropine-injected MD chicks was associated with a marked reduction in the relative axial elongation of the deprived eye (0.21 mm) when compared to saline-injected or sham-injected MD chicks (1.04 mm and 1.00 mm). This reduction in axial length in atropine-injected MD chicks was predominantly the result of a reduction in vitreous chamber elongation, although a reduction in anterior segment depth also was observed. Mean equatorial diameter was significantly reduced in atropine-injected MD chicks compared to saline-injected and sham-injected MD chicks, although to a lesser extent. Control experiments demonstrated that intravitreally injected atropine did not reduce carbachol-induced accommodation or light-induced pupil constriction in the skeletal intraocular muscles of the chick eye.These findings demonstrate that chronic administration of the muscarinic antagonist atropine prevents experimentally induced myopia in chick via a nonaccommodative mechanism.