"Sudden vision change"

My dad is in his 80s and had a sudden change is his vision. I phoned NHS24 and was told to take him to an optician. It was after 3pm on a Saturday when I was told this. I asked if I should take him to an optician straight away they said - it's up to you. 

I didn't manage to get an appointment until the next day. Optician sent my dad to the hospital and the hospital confirmed that that my dad has had a stroke.  I thought every minute counted if someone has had a stroke.

Surely at his age he should have been given a scan at the hospital without having to go see an optician first. Why not err on the side of caution rather than dismiss someone?  My dad remains in hospital.