Years ago I had an older female colleague and we had to go on a road trip - visiting various clients all over Wales and the border areas of England. She was driving in her own car.
In the course of one day we drove from the area where we lived in North West Wales into Liverpool, down to Stratford, Gloucester, Bath, Bristol, back into South Wales over the Severn bridge and then back up North to where we came from. I was in my 20s and she was then in her late 40s, and a very opinionated know-it-all woman with quite a high position in the company, and I was very much the junior colleague.
I know she had sight problems and had mentioned on more than one occasion that she was blind in one eye. I don't know if she was fully or partially blind in that eye or what, but she did wear very thick lensed glasses, although her sight (or lack of it) didn't seem to affect her at work or in everyday life.
So off we went, made all the various visits and as we got back into Wales it started to get dark. The latter twisty twiny Wales up mountains down valleys part of the journey was a total nightmare on account of her driving with dipped beam all the time along unlit, pitch black, rural and often precarious roads, and then when a car appeared in the opposite direction she would hit the full beam, totally blinding the oncoming driver who in some instances (if they weren't too stunned to react) would flash and beep furiously with her muttering 'arsehole' or 'fuck off' or similar.
I was astounded and thought she'd realise what she was doing wrong, but she didn't. I tried to tell her that she was using her lights the wrong way round and that she should be driving on full beam and dipping when she saw another car, but she wasn't having any of it. She seemed completely unable to grasp what I was saying and what she was doing - I don't know if it was deliberate, unintentional or what. 
I was a nervous bloody wreck by the time we got back and never, ever got in a car with her again.