As an ophthalmologist, I can tell you that most of my patients prefer
progressive, or Varilux lenses, for most occupations. For birding I don't
think they have any advantage over standard bifocals, and may even be worse,
as the bifocal segment often intrudes into the distance portion of the lens.
For using a scope or binoculars, you will only be using the upper part of
your lenses, and if the seg is too high it will intrude.

Here are some caveats:

Progressive lenses are best for first time users; those used to a standard
bifocal often have trouble switching, as there is more aberation in the
peripheral part of the lenses.

Prog lenses primary advantage is that they provide clear vision at any
distance, whereas bifocals give you two distinct zones, far vision and
reading vision. Varilux type are great for computer users.

Fitting and adjustment of progressive lenses is critical, and is best done
by an experienced optician. Also, the quality of the lenses varies greatly:
good brands are Varilux, Seiko, Zeiss and a few others.
You get what you pay for, as in binoculars and scopes.


Wm Mulligan

Seattle WA 98136


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