Candidates will undergo a medical history, physical examination, eye examination and blood test. The eye examination includes measurement of eye pressure and dilation of the pupils to fully examine the lens, vitreous and retina. Specialized tests will be done only if needed to determine eligibility for a nystagmus or strabismus study. These include routine laboratory tests, non-invasive imaging, questionnaires, and other standard tests. If needed, a test called oculography may be done to record eye movements. There are two procedures for recording and documenting these movements. In the infrared system, the patient wears a pair of glasses or goggles and looks at a red light while the head is kept steady. In the search coil system, the eye is numbed with anesthetic eye drops and a soft contact lens is placed on the eye. Then the patient looks at a red light while the head is held still. Each oculography session lasts 20 to 30 minutes. Photographs of the eye may be taken.