A method for diagnosing a disease state in a subject, including examining the subject's eyes in order to determine whether the subject exhibits one or more symptoms of the disease state. Symptoms of the disease state include altered ocular characteristics, such as pupil size, pupil motility, ocular blood vessel coloration, and strobe light cutoff frequency. By evaluating changes to ocular characteristics, a disease state can be diagnosed in a subject. In addition, the severity of the disease state also can be determined.