Relationships Among Pupil Responses to Light, Circadian Rhythms, and Sleep

The investigators are studying relationships among eye pathology, pupil responses to light, sleep, circadian rhythms, and hormones in healthy individuals and those with various medical disorders or illnesses. All participants will: * Answer questionnaires about their health * Receive an eye exam, * For one week at home, participants will track their sleep and wake using actigraphy (wrist worn wearable) and an online sleep diary. * Complete a pupillometry session (measuring pupil size in response to different lighting) at MGH Participants may also choose to participate in the following additional procedures in any order: * Within one week of their pupillometry session, an at-home saliva collection under dim light. Saliva melatonin can be analyzed to determine Dim-Light-Melatonin-Onset (DLMO), a marker of circadian timing. * If participants participate in one night saliva collection, a second night of at-home saliva collection with a bright light exposure to calculate melatonin suppression in response to light.

Inclusion Criteria: * 18-85 years old. * stable medically * ability to speak, understand and read English at a high school level Exclusion Criteria: * any history of eye trauma or surgery besides correctable vision abnormalities (e.g., with glasses); any abnormalities on clinical eye exam (e.g., neuritis, Neuromyelitis optica, untreated glaucoma) such that the ophthalmologist recommends the participant not be studied; * prescription or non-prescription drugs affecting the pupil (e.g., affecting autonomic function), sleep, melatonin (e.g., lithium, alpha- and beta-adrenergic antagonists), and/or circadian rhythms (e.g., beta blockers, non-steroidal anti-inflammatory drugs, tricyclics\\ * shift- or night-work in past three months; * crossing more than 2 time zones in past three months; * pregnant or less than 6 months post-partum or breastfeeding.