When you turn 85, if you want to keep your unrestricted car driver's licence, you'll need to do a practical driving test every second year (at 85, 87, 89 etc). This is in addition to your yearly medical examination.
You can either do the driving test with a Roads and Maritime Services testing officer, or be assessed by an older driver assessor. These assessors are driving instructors accredited by Roads and Maritime, and they charge a fee.
You can find a local older driver assessor online.Find an assessor