Senior citizens should have to retake an eye exam and a drivers test because there have been more accidents with senior citizens then there have been with teenagers. Also as they age health problems and many others things come upon in life and they need to make sure they are in the best condition to drive.
I think when it comes to age limits in driving, I don't know a very old person should have no choice but to give up their right to drive after they reach a certain age; but, I do think once they hit 65-70, they should have to take an eye exam.
Some elderly people just can't drive. When people get older, they should have their driving skills re-tested every year or two instead of every six years like in some states. Perhaps states should start regular tests on the elderly at age 65 or age 70 as a precaution against other drivers. It's nothing against the elderly, it's just that their ability to drive can change very quickly due to health concerns or just because they get older.
Everyone ages differently, some people are of perfect and sound mind at 100 years of age while some are in retirement homes in their late 60's, I believe overall unless you are involved in traffic violations that end up suspending your license then you should be able to keep it no matter your age.
I don't think we need age limits on the upper end for driving. Competency can vary dramatically from person to person. What we should do around the age of 65 is start handing out licenses for only 18 months at a time. In order to get the license renewed, the senior must take another driving test.