Medical disability

We have an employee who has worked for our department for over 20 years. He is a Vietnam War Veteran and received a medical discharge from the military for injuries sustained during combat. He was hired in our department as a Printer. Over the years, his medical condition has deteriated. His previous supervisors created new positions for him that would allow him to continue working but remove him from working with the equipment that posed a danger should he seize while operating it. He goes through periods of having frequent seizures. He knows before he is going to have one and is good about getting help from one of his co-workers so that he doesn't injure himself or others. Recently, his doctor has prescribed Valium that he is to take when he feels a seizure coming on. The employee has given his supervisor and co-workers these instructions and asked them to make sure he takes it when he tells them that he is getting ready to seize. I have real concerns that his co-workers are being asked to help medicate him and have become his caretakers. He doesn't want to be at home alone so he comes to work often when we feel he shouldn't be here. When he has a seizure, we call his wife and she eventually comes to pick him up. We have told him that we are going to begin calling 911 when this happens so that he is sure to receive the proper care and if he needs to be transported he can be. He doesn't want the cost of the ambulance so he would prefer that we not call.

In addition to all this, his performance is slipping. His errors have cost us thousands of dollars to correct not to mention the money we've lost because customers don't want to use the service he provides. He received an unsatisfactory evaluation and was extremely unhappy about it because we know of his condition. We have had an essential function review of his position and I have requested his physician to review the essential functions and the full position description and tell us if the employee can perform the job with or without accommodations. I did this in early June. To date I have heard nothing from the doctor. I have asked the employee a couple of times how things are progressing and he has indicated his doctor has the information but has not yet responded. This employee puts forth 110% but simply can not physically or mentally perform the job. We would prefer to help him leave on a medical disability rather than terminate him. Any advice on how I should proceed? Thanks!