Occasionally, I see mentioned in a post that someone is
having to turn to an AF camera system due to eyesight changes.
As we age, our ability to focus our eyes diminishes, and first
bifocals, then trifocals become necessary to be able to see at
varying distances. I mentioned in a post some time ago that I
was thinking of trying another solution - which, if it worked,
would also optimize my vision for being able to continue to use
the 35mm SLR camera ground glass viewing screen for focusing
(I have never liked AF, or those miserable "focusing aids"
that clutter the centers of some viewing screens).

Having gotten around to having an unusual pair of glasses made
(the loss of ability to focus with a Nikon F2, followed by the
6006 and N90, and most recently, the FA/FE/FM [the 8008 and F3
continued to be OK, but more difficult to use than previously],
prompted me to try), I am happy to report that the new glasses
work well (with a bit of a reservation, alas).

First, I will describe what my situation is: I am (differently)
nearsighted in both eyes, and unable to focus over a wide range,
even with bifocals. I am unwilling to turn to trifocals (the line
of the bifocal bothers me, so I do not want to add another - and
I need a larger lens area for camera viewing than the middle lens
of a trifocal would provide [I found lineless lenses totally
useless, since the sharp viewing angle in both the distance and
close parts is VERY restricted, and I like wide-angle vision]).

My current glasses have large lenses, with 25mm flat-top
bifocal insets set unusually low to keep them out of the way
while using a camera. The main lenses are set for good distance
vision, and the bifocals are both set for about two feet (I can
see well at about one foot without glasses). This provides good
wide-field distance vision (including a good view of the ground),
and good near-field vision, but the area between about six feet
and two and one half feet is not sharp - nor is the area closer
than about one and one half feet (the camera viewfinder screen
apparent distance must be about four feet, and I just miss it
with these glasses).

My new glasses have the right distance-lens set for optimum
infinity sharpness, the left (camera focusing eye) has +.5
diopter added to bring the optimum distance to about three and
one half feet, the right bifocal (25mm flat-top set low in the
distance lens) is set for about 22 inches, and the left bifocal
is set for about 17 inches. This provides a continuous range of
sharp focus from infinity to about 15 inches. I can now see all
Nikon viewing screens VERY sharply, which makes manual focusing
easy and reliable (astigmatism, and having many camera bodies,
discouraged me from placing corrective lenses in each camera
eyepiece). I can now also see well (after a short period of
adjustment to a bit of monocular vision) under all conditions
except long-distance in low-light. For that, I have another pair
of glasses with .25 diopter less under-correction for the left
eye (.25 diopter undercorrected for best distance vision), with
everything else remaining the same (it is possible to focus a
camera with this second pair [intended for movies and night
driving], though not so easily as with the first pair - though
low-light distance vision improved). I was hoping to get away
with one pair of glasses for all purposes, but it didn't
work out that way, alas (but almost......:).

Hope This Helps