Digital BW, The Print

Eyesight problems are tough on photographers, and I am impressed with your
persistence despite it.  Here are a few suggestions:

I had special bi-focals made, the top part is corrected for infinity, the
bottom part is corrected for looking through a viewfinder.  The doctor who
examined me was an amateur photographer and understood exactly what I
needed.  These glasses are weird, you cannot see your feet in front of you,
but they make short and sure work of your shot.  I bought them years ago
when I came back from a shoot with thirty rolls of out-of-focus film,
(whenever possible, I use a view camera, and I never have problems with
ground glass focusing)

Nikon makes eyepiece adapters for some of their cameras, but these get mixed
reviews on the several internet discussions that I have read, so try them
before buying any of them, with all your lenses individually.  I did buy one
for Hassleblad, and what a good difference that made!

Nikon makes alternative screens with larger rangefinder section in the
middle, but it does not work on any lens longer than about 105mm in my
personal experience (it blacks out)

A Beattie screen for your Nikon would give you a whole F stop brighter view
in your finder.  Most big camera stores have a sample or demo camera that
you can see for yourself.  This is a process where the screen is coated with
a luminous material, so probably any screen that a camera repairman can
remove from a camera could be coated.  I don't have any knowledge of how it
would work on specific models of digital cameras.

Best of luck with your photography!

Tom Robinson