Oh, ffs!
Ben, have you never heard of glasses?
Contact lenses?
Eyetests?
I reckon your grandad PROBABLY had to have his sight checked out before he was granted a driving license? If not, he bloody well should have IMO.
PLUS this guy had JUST lost the sight in one eye. Try that. Get your bike out, ride it round the garden for a bit, then tape one eye shut, or wear an eyepatch, and do the same thing again. Don't forget to perform manouvers that require you to judge speed and distance.
You might want to put a lid on before trying it though. Wouldn't want you to hurt yourself. Honest.
Its one thing being used to only having the use of one eye, quite another to suddenly being deprived of stereoscopic vision.
Si(C)