Several things happen to everyone's eyesight as they age.
First your eye's ability to change it's focal length decreases. This is why you need either reading glasses or longer arms.
Second your eyes sensitivity to light becomes worse i.e your night vision decreases. Strangely eating carrots helps this. In WW2 the British fed their Spitfire pilots lots of carrots to help increase their night vision during the battle of Britain. I've read they ate so many carrots their skin started to look kind of orange.
There are also a long list of things that can go wrong with your eyes in addition to the above.
In my case I developed bad astigmatism and a cataract in one eye. Surgery corrected the cataract and glasses have fixed the rest that is correctable i.e. loss if night vision is not.
I use the prescription from the top half of my bi-focals to play golf mounted in the large frames so the glass edge is not visible during a swing. This can be a problem since I have really wide peripheral vision.
My golf glasses consist of two pairs, one clear and one copper tinted sunglasses both with anti glare coating. The clear is for cloudy days (see night vision above). My every day bi-focal glasses are transition lenses.