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 aim of this study is to characterize the effects of atropine on choroidal thickness and the influence of time of administration (am vs pm). It is hypothesized that the atropine's effect on choroidal thickness will vary with baseline thickness related to diurnal rhythm, where thicker baseline thickness will show a reduced choroidal response.

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.

Inclusion Criteria:

• Good general and ocular health
• Soft contact lens wearers to cease lens wear for at least 24 hours
• No previous rigid gas permeable lens wear

Exclusion Criteria:

• History of ocular surgery, including refractive surgery
• Amblyopia
• Use of ocular medications
• Known allergies or sensitivity to atropine
• Pregnant, plan to become pregnant, or are breastfeeding
• Taking monoamine oxidase inhibitors (MAOIs)

All IPD collected from the study will be made available to other the investigators that have been listed on this study. IPD will be de-identified before making it available to the other investigators. IPD will become available after the end of study data collection. Deidentified IPD will be obtained by other investigator in excel files sent by the primary investigator