How much does LENS SIZE affect vision....?

My dad was asking me about his reading glasses. His glasses, which
were prescribed about 10 years ago for reading still work great. He
has no problems reading whatsoever.

His glasses are somewhat big though, or so it seems. The dimension of
his glasses are roughly 1 3-4" X 1 1/2". they SEEM larger than
some of the glasses I see today.

Now.. Is there are reason why some lenses are bigger than others?
And... does the size of the lenses affect the vision in any way? ie..
visual field etc...

So... To sum up here. What are the pros and cons of bigger and
smaller type lenses? Or.... is it purely "cosmetic".

Thanks LEESA

PS: My dad is FARSIGHTED with some astigmatism in both eyes.

 

The recent trend for very small lenses is a fashion trend, not a medical
one. But it has made possible by stronger frame materials (which need less
bracing at the bridge) and more sophisticated lens designs which enable a
smaller lens.

The benefits of a smaller frame is mostly cosmetic, but a smaller lens is
lighter and less likely to slip out of position on the face (which can
adversely affect vision). A larger lens will usually offer better peripheral
vision.

With a progressive lens (with a separate reading, distance area and
intermediate transition zone) a larger lens often has larger reading and
distance viewing areas. But once you get to a certain size, then going
larger does not have much additional benefit.