Study 1: Subjects participating in this portion of the study will attend one single visit: 1) Informed consent will be obtained and inclusion/exclusion criteria will be confirmed. Demographic information, ocular history, refraction, and visual acuity information will be collected for all patients. Additional clinical data will also be collected for Study 1B participants only. Information to be collected will include name, date of birth, ethnicity, gender, ocular history (surgery, etc), type of glaucoma (Study 1B), current visual acuity, refraction, central corneal thickness (Study 1B), intraocular pressure (Study 1B), recent slit lamp exam including lens status (Study 1B), recent dilated exam including optic nerve appearance (Study 1B), and recent automated perimetry results (Humphrey visual field, Study 1B) 2) Snellen visual acuity will be measured while wearing current spectacle correction to ensure acuity of 20/40 or better. The current spectacle correction (refraction) and acuity will be recorded. 3) OKR (optokinetic reflex)-based contrast testing will be performed with the OCD - optokinetic contrast device (the device in study with this protocol). Subjects will be shown a brief demonstration of the OCD under red light (to begin dark adaptation) to familiarize themselves with the device and the expected testing strategy. 4) Subjects will then be dark adapted for 20-30 minutes. During this time they will be sitting in a darkened room. If the room is not dark enough a loose blindfold may be used. Music options will be available to help pass the time and ease potential discomfort. 5) After 20-30 minutes the blindfold will be removed (if used) and patient will have monocular dark-adapted (scotopic) testing done with the OCD, left eye followed by right eye. The non-tested eye may be covered during testing. After scotopic testing, the light of the OCD will be increased and light-adapted (photopic) testing will be performed in the same manner. 6) Debriefing. Subjective assessments of the testing modality and dark adaptation process will be collected.