The study aims to examine how the vascular layer of the eyeball (choroidal layer) responds when part of the visual field is exposed to specially generated visual stimulus. The study goal will be accomplished by producing specific blur visual stimulus at a particular visual field position and measure any consistent thickness change pattern in the choroidal layer.

We propose to test the hypothesis that regional changes in the choroidal thickness may be induced differently after short-term exposure to specific visual stimuli.

Inclusion Criteria:

A person is eligible for inclusion in the study if he/she:

• Is between the ages of 18 and 40 yrs old
• Has normal best corrected visual acuity being 20/20 or better
• Has spherical refractive error between +1.00D and -6.00D.
• Is capable of fixating on the target.
• Has no prior ocular surgery.
• Has no ocular pathology except keratoconus.
• Can tolerate dilating eye drops

Exclusion Criteria:

A person will be excluded from the study if he/she:

• Does not fall within above mentioned age group.
• Has chronic or systemic eye disease that would interfere with pupil dilation via eye drops.
• Underwent ocular surgeries or history of ocular trauma
• Has shallow anterior chamber angle and/or glaucoma.
• Has clinically significant dry eye.
• Has signs of any choroidal or retinal pathology, and abnormalities in the visual pathway
• Has spherical refractive error that exceeds the limits outlined above.
• Has binocular anomalies (e.g. convergence insufficiency, strabismus, pseudo-myopia, amblyopia).
• Is an adult unable to consent
• Is an individual who is not yet adult (infants, children, teenagers)
• Is a pregnant woman
• Is a prisoner
• Is a student for whom you have direct access to/influence on grades
• Is an economically and/or educationally disadvantaged person