Utility of Quantification of Afferent Pupillary Defect in Predicting Optic Nerve Disease in Retrobulbar Neuritis, Multiple Sclerosis and Neuromyelitis Optica Spectrum Disease - a Retrospective and Prospective Analysis

The purpose of this research is to gather information on whether using quantitative- or numerical measurements of pupil changes as an alternative to qualitative- or observation based- testing can be done to assess optic nerve dysfunction in ON, MS with ON, and NMOSD with ON. One way this is done is through evaluating relative afferent pupillary defect (RAPD), which is a clinical sign that is used to detect an injury or defect in the pupil's pathway and this often involves the retina of the eye, which focuses light, and the optic nerve, which sends visual information to the brain. When shining a light into each eye, the eye with RAPD shows a slowed response to light, and when the light moves to the normal eye, the pupil of RAPD eye will dilate. Observational evaluations of RAPD are very common in clinical neurology to detect these optic nerve diseases. As technology has advanced, to lessen the observation errors, numerical measurement of RAPD is now possible through a web based app called Reflex (Brightlamp Inc., Purdue University), which is a FDAapproved class I regulated medical device. In this study, the investigator will compare the results of a participant's app recording to other data that has been collected which also tracks optic nerve function status.