Glaucoma is often more severe in one eye and this fact can be exploited in screening tests. The investigators plan to use a novel screening device that very accurately records the pupillary response from each eye. It is likely that patients with glaucoma will have abnormal responses when measured, and by comparing responses between the two eyes the investigators will be able to determine who has glaucoma. If this test works well, it will provide a low-cost way to screen populations at risk for glaucoma. Furthermore, this research will expand the knowledge base regarding how pupil responses to light differ between persons with and without glaucoma. Insights gained from this study will be useful in the development of an effective screening tool in the detection of glaucoma.