The Influence of Atropine on Choroidal Thickness

Atropine eye drops are increasingly prescribed for the management of progressive myopia or short-sightedness. A previous study suggested that the back of the eye or choroid may be a part of the mechanism by which it induces its effects. The choroid shows diurnal variation and the efficacy of atropine on myopia control in relationship to the patient's baseline choroidal thickness is unknown. Thus, the objective of this study is to provide data to characterize the influence of atropine on choroid thickness. The study aims are to: 1. Determine the effect of am or pm atropine application on choroid thickness 2. Determine the effect of atropine on choroid thickness in relationship to baseline thickness Participants will be asked to attend a screening session and 13 study visits. Following the screening visit, participants will be scheduled to return for 4 visits across 12 hours (4 hour intervals starting from 8am) in a single day where eye shape measurements will be taken to characterize diurnal variations in eye shape. Subjects will then be randomized to receive a drop of 1% atropine eye drops in both eyes in the morning or a night. Measurements of the shape of the front and back of the eye will be taken after approximately 1, 12, 24 and 96 hours after drop instillation. After a 2 week washout period, 1% atropine eye drops will be administered either in the morning or at night (the visit that was not previously scheduled) and measurements of the shape of the front and back of the eye will be taken after approximately 1, 12, 24 and 96 hours after drop instillation.