I know someone who's legally blind yet driving how do I turn them in

If you are aware that someone is driving although they should not be you should report it to the Department of Motor Vehicles. This is not limited to just vision issues. The DMV will then send the driver a medical review request which will require them to take a vision test, road test, or provide documentation from a doctor stating that they are capable of safely operating a vehicle.

You can find the Driver Condition/Behavior report form by clicking on the link. It will direct you to the DMV website. The form will come up as a PDF file where you can then fill in the form and print it or print the blank form then fill it in by hand. The form does require that all fields be filled in so make sure it is complete, the form also requires a signature. You can then either mail the form to the address provided or take it to your local DMV office and turn it in there.