Driving over 70
Once you reach 70 you need to renew your driving licence, and then do so again every three years. All it involves is completing a form to self-certify that you're OK to continue driving. There's no additional driving test or any formal checks that need to be done, although DVLA might contact you if they have any queries.
If you've developed any medical conditions you'll need to advise your insurer and DVLA. Failing to do that could get you a fine and penalty points on your licence.
Make sure you understand whether the condition means there’s anything to be aware of when it comes to driving. There could be implications linked either to the condition or as a result of side effects from your medication. Seek your doctor's advice.