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Atropine Dose to Treat Myopia

2012; Elsevier BV; Volume: 119; Issue: 8 Linguagem: Inglês

10.1016/j.ophtha.2012.05.014

1549-4713

Virgilio Galvis, Alejandro Tello, Carlos J. Rodríguez, Juan José Rey,

Glaucoma and retinal disorders

We read with interest the study on atropine and myopia by Chia et al.1Chia A. Chua W.H. Cheung Y.B. et al.Atropine for the treatment of childhood myopia: safety and efficacy of 0.5%, 0.1%, and 0.01% doses (atropine for the treatment of myopia 2).Ophthalmology. 2012; 119: 347-354Abstract Full Text Full Text PDF PubMed Scopus (402) Google Scholar Their conclusion about using atropine 0.01% in controlling myopia progression, with comparable efficacy compared to higher doses but with fewer side effects, is very appealing. In the article the authors indicate: “… subsequent studies have shown that atropine also inhibits myopia in animals (e.g., in chickens) that have no accommodative facility.” This statement is incorrect since chickens do accommodate. In fact, while mammals show only lenticular changes during the accommodative effort, chicks have the possibility of changing both the cornea and the lens during accommodation.2Pilar G. Nuñez R. McLennan I.S. Meriney S.D. Muscarinic and nicotinic synaptic activation of the developing chicken iris.J Neurosci. 1987; 7: 3813-3826PubMed Google Scholar Possibly, the concept that the authors wanted to mention is that the effect of atropine on the progression of myopia in chickens is not related with accommodation. McBrien et al proved this point early in the 1990s when they showed that administration of intravitreal injections of atropine prevented experimentally induced myopia in chicks via a nonaccommodative mechanism. The degree of accommodation induced by corneal iontophoresis of 10% carbachol was similar in atropine-injected and saline-injected eyes of the chicks.3McBrien N.A. Moghaddam H.O. Reeder A.P. Atropine reduces experimental myopia and eye enlargement via a nonaccommodative mechanism.Invest Ophthalmol Vis Sci. 1993; 34: 205-215PubMed Google Scholar The explanation of this is that unlike mammals, the iris and ciliary muscles of chickens are striated and contract through activation of nicotinic receptors, and therefore are unresponsive to muscarinic blockage caused by atropine.2Pilar G. Nuñez R. McLennan I.S. Meriney S.D. Muscarinic and nicotinic synaptic activation of the developing chicken iris.J Neurosci. 1987; 7: 3813-3826PubMed Google Scholar We think that the work of Chia et al sheds light on one question: what is the minimal dose that allows the best efficacy? However, we think another question remains: “what is the lower frequency of administration of atropine that is effective?” It has been known that a single drop of atropine has an effect lasting several days.4Wolf A.V. Hodge H.C. Effects of atropine sulfate, methyl-atropine nitrate (Metropine) and homatropine hydrobromide on adult human eyes.Arch Ophthalmol. 1946; 36: 293Crossref Scopus (10) Google Scholar Several studies have compared daily atropine to different regimens in amblyopic children. A prospective, randomized clinical trial found that weekend atropine appeared to be as effective as daily atropine in treating children with moderate amblyopia.5Repka M.X. Cotter S.A. Beck R.W. Pediatric Eye Disease Investigator GroupA randomized trial of atropine regimens for treatment of moderate amblyopia in children.Ophthalmology. 2004; 111: 2076-2085Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar We are not aware of any studies using topical atropine intermittent regimen (once or twice a week) to treat myopia. We have been using once a week 1% atropine in a group of 33 patients (66 eyes), along with ocular hypotensives (between 6 and 16 years of age; mean, 11.9 years) and we have found high acceptability. Baseline spherical equivalent was −4.52 D. At 1 year follow up the spherical equivalent was −4.46 D (P = 0.015, Student t distribution). This statistically significant reduction of the myopia magnitude we believe is due to the hyperopic shift secondary to cyclopegic effect of atropine. With these preliminary results we think that reducing the frequency of administration of 1% atropine could be an alternative to reducing the concentration of atropine in myopia progression control. Atropine for the Treatment of Childhood Myopia: Safety and Efficacy of 0.5%, 0.1%, and 0.01% Doses (Atropine for the Treatment of Myopia 2)OphthalmologyVol. 119Issue 2PreviewOur previous study, Atropine for the Treatment of Myopia 1 (ATOM1), showed that atropine 1% eyedrops were effective in controlling myopic progression but with visual side effects resulting from cycloplegia and mydriasis. The aim of this study was to compare efficacy and visual side effects of 3 lower doses of atropine: 0.5%, 0.1%, and 0.01%. Full-Text PDF Author replyOphthalmologyVol. 119Issue 8PreviewWe thank Galvis et al for their letter. Indeed, the point we wanted to make was that the effect of atropine may be through nonaccommodative pathway.1 The results of their weekly atropine 1% dose together with ocular hypotensive are interesting, and as our paper suggests,2 smaller total doses of atropine appear sufficient to slow myopia progression. However, one would assume that significant pupil dilation and loss of accommodation with the 1% concentration would still occur at least during the first part of the week after eyedrop application, and the convenience of the once-weekly dose, would still be offset by these side effects. Full-Text PDF