Duration and effect of single-dose atropine: paralysis of accommodation in penalization treatment of functional amblyopia

Abstract

Background and purpose: Atropine dilates the pupil and paralyzes the ciliary muscle accommodation, blurring vision, and therefore is an effective penalization of the sound eye in the treatment of functional amblyopia of the other eye. The degree of blur induced is a function of the amount of the patient's uncorrected hyperopia and the distance from the eye of the viewed material or object. Another factor determining effectiveness of atropine penalization is the duration of the effect of the atropine. It is the purpose of this study to investigate these factors.

Methods: Six normal children underwent complete eye exam with cycloplegic refraction several days before deliberate instillation of atropine 1% in the sound, or right eye. Distance and near acuity was then tested after 30 minutes, and on subsequent days. Additional data points were derived by placing known minus lenses in front of the tested eye. In addition, we also studied one successfully treated amblyopic patient when he terminated chronic daily atropine in his normal, sound eye.

Results: Atropine initially produced a linear reduction in logMAR acuity (blur) at distance of about 0.2 logMAR lines per diopters of uncorrected hyperopia. The magnitude of the blur was greater for near, but the effect of increased hyperopia was slightly greater for distance measurements. This blurring of acuity lasted just less than 48 hours for normal subjects, and just over 48 hours following prompt cessation of chronic daily atropine in that one subject. Regression formulae were derived relating uncorrected hyperopia and time interval following atropine cessation on distance and near acuity in children of amblyopic age range.

Conclusion: The degree of penalization is highly dependent on the uncorrected hyperopic refractive error. A significant penalization effect is present only for one day or so. Daily atropine is therefore indicated for penalization. To better tailor penalization therapy to target sound eye acuity blur, these formulae and graphs can be used, specifically, in addition, to determine the amount of deliberate spectacle hyperopic undercorrection to maximize the penalization effect.