I see this as a real problematic issue.
Obviously if an elderly person is racked with nerve pain throughout the day, he is not capable of looking over his shoulder, moving his body while driving, or moving his foot from one pedal to the other.
Also, if a person has been diagnosed with diabetes retinopathy, which affects vision, then he is not able to drive well.
I don't care how long the person has been driving. I don't care how it would affect his personal feelings. I don't care if someone in this condition, and especially in their mid 80s, feels that this is an attack on the elderly.
Someone who mistakes a solid green light for a green arrow, and turns, and the other cars are able to stop in time, then the elderly driver is not capable of driving.
When there is a problem, when a crash occurs, then those injured by the elderly person need to do the following: go after his assets, go after his family members (for not doing something about this problem - it is there responsibility and obligation to take care of these people), and go after the elderly person's physicians - all of them. If they are prescribing medication for a persons myriad medical ailments, including diabetes retinopathy, nerve pain, then these physicians are very aware of the person's ability, or lack thereof, of being behind the wheel of a car.
All of these persons mentioned above need to be responsible for the elderly's actions - those in their care. Otherwise, then they should all be dealt with in a court of law.