The Relative Prevalence and Severity of Autonomic Nervous System Dysfunction

Inclusion Criteria: * Type I and Type II Diabetic patients 19 or older who are scheduled for elective surgery to improve vision impaired by diabetic retinopathy * Patients scheduled during the same time period without diabetes for retinal surgery will serve as an age and gender matched reference group to undergo the non-invasive ANS testing on the day of surgery Exclusion Criteria: * Inability to stand will only do baseline, deep breathing and Valsalva portions (A-D) of the testing as described in section 8.1 * Patients with syncope on standing will only do portions A-D of the test * Inability to cooperate with deep breathing and Valsalva * Tracheoscopy or otherwise not able to perform a Valsalva * Not desiring to participate after informed consent * Known history of idiopathic dysautonomia * Pulmonary difficulties associated with hyperventilation, including acute URI * Pacemaker dependent * Persistently high intraocular pressure despite treatment * Atrial fibrillation * Ventricular arrhythmias greater than 10 beats per minute * Taking MAO inhibitors