Four Distance Glasses - David Ruether

I have myopia combined with astigmatism and age-related inability to focus. I had a pair of glasses made that corrected for four distances by distributing the four different distance corrections among the two main lenses
and the two bifocals (there are single bifocal lenses
in each side, for a total of four glasses lens
focal-lengths/corrections). What is different from
standard bi-focal glasses corrections set-up is that one distance lens is assigned infinity-focus (to take care of sharp distance vision), the other (for the predominant eye for camera users) one-meter-focus (to take care of the
mid-distance normally lost in normal bifocal set-ups, and
to optimize one main glasses lens for the camera viewfinder effective viewing distance of about 3.5'); the bifocal in the "infinity" lens is set for about 2' (longer than usual, but useful for the "magazine in lap" distance) and the bifocal in the "one-meter" lens is set for about 1.5'
(suitable for most short-term reading and other fairly close viewing - other glasses are used for extended reading and for computer work, and I remove the glasses for really
close work). This gives good corrections for four different distances within the usual bifocal-glasses lens arrangement, without the usual abrupt large shifts in distance settings between the distance lenses and the inset lenses. With the small (25-28mm) flat-top inset lenses set lower than normal, I have complete continuously-sharp smooth-focus vision from a bit under 1.5' to infinity (with no sense of "mono-vision" in the four-distance lens settings since the FL "errors" between them are minor), good "mid-distance" vision (which is often missing from standard bifocals), a sharp view of the camera viewfinder (normally missing), and wide-angle vision (unlike with narrow-angle "lineless" or "progressive" lens glasses which limit horizontal sharpness - and unlike with standard bifocals with the bifocal inset lenses set
for too close a viewing distance, or made too large to see distant things around them, or set too high for a good optimization of sharpness corrections in the vertical direction). It took about 2 weeks to feel comfortable with night driving and movie watching (the camera eye tends at first to predominate when it is dark, or when the subject does not have a lot of well-defined detail, but closing the predominant eye for a moment corrects this) - but for everything now, continuous sharp focus over a wide range
of distances and angles has been restored.

It is hard to get some optometrists to "break the rules" and set the small bifocal insets lower than normal (and properly "tilt" the straight top edges for least visibility) and have the distances set for around 1.5' and 2' (let alone set one of the main lenses "wrong") - but it is worth the effort to find one that will. I have been using glasses made this way for about 15 years, and they continue to work well for me and provide noticeable improvements in vision compared with the alternatives...

Since writing the above, aging beyond 65 has further reduced my ability to focus (presbyopia), and I have modified the glasses described above by narrowing the differences between the four lens focal lengths. While
this has moved the minimum distance for sharp vision outward, the loss is minor, and good continuous vision
from far to near has been restored. As described above,
for computer viewing and most reading, I had a pair of glasses made with the bifocal corrections used for the
two simple lenses...

"Hope This Helps"
David Ruether (d_ruether@hotmail.com)

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