A couple of months ago someone posted about a pair of special
bifocals they had made. I finally got a pair, and let me say that
these things are FANTASTIC !
You get a big frame with your reading prescription on top, and 2X
(twice) that on the bottom. I opted for tempered glass, and I
recommend that the lower lens be set no higher than about halfway.
How do I love them ? Nothing to wear around my head, nothing to flip
up or down. They don’t interfere with my headphones or my dust masks.
No headband hair. Better optical quality than an Optivisor/glasses
combo. Lighter! Easier, more versatile. They work with an Optivisor
if you need it, even with the add-on loupe.
I would never go back. So, to all you vision-compromised Orchidians,
check it out! And thanks again to the original poster.
I too, had a similar pair made up by an optician friend, called an
"Executive Bifocal", and they are terrific. I have them set up in a
wire frame, polycarbonate lenses, with a scratch-resistant coating.
My prescription is on the top, and a 2.50 add below for a 12-13 inch.
working distance. The division line is just about midway on the
lense. I have great magnification at the bench, and when I look up, I
have my normal distance vision around the studio. The plastic lenses
are going to be the way to go over glass lenses, as the glass ones I
had made at first were so heavy they slid down my nose.
The size of the lense makes for effective safety glasses, as well,
so I don’t have to worry about working with the flex shaft or
buffers. I’d never go back to a “head-band” type of magnifier.
I can see better than a cat in the dark when looking at things far
away. My prescription tri focals now offer me 4" 12" & 20"
distances. I take off the glasses when I need to walk around a room.
Better than the hoods … this configuration doesn’t make me dizzy
when I look up.
I also had my Opthamologist write me a prescription for my regular
prescription in the top and a super bifocal in the bottom for close
work. Only problem is sometimes I forget I am wearing them and when
I go down the steps I almost kill myself!!! They are great for the
bench, but be careful!!!
Magnifying bifocals of the type being discussed are not available in
a regular store, they are custom-made at an optical shop. I believe
I was the one who described my shop glasses… because I am of “that
age”, I found a 1/2 reading prescription (or “intermediate vision”)
for the distance to my torch, and then 2x my reading for the bottom,
was pretty good for my studio setup. (I would probably go 2.25 at
least on the bottom if I was doing it again. 3x was too much!) Your
mileage will absolutely vary, because a good prescription depends
heavily on accurate measures of distance being matched against your
optical correction, if any. The best thing to do is to take a lot of
measurements, hie thee to your favorite optical dispensary, and sit
down with a good optician. As Silvermason and Jay Whaley noted, when
you get a larger frame you eliminate the need for an optivisor and
safety eyewear (over glasses for those who need those too), and you
leave yourself a lot of room to actually see in the two magnification
areas. Many of us already use a progressive lens, or a no-line
bifocal, in everyday glasses but those lenses have a very limited
channel of clarity and a lot of distortion on the sides. The lined
large bifocal provides a wide clear field of vision.
I just went to my optometrist and had them made. I have not found the
tempered glass to be too heavy, and I just feel that the durability
and cleanability of glass is better than plastic lenses. Even
polycarbonate is pretty vulnerable in my experience.
If you do need reading glasses, I would definitely recommend the
reading prescription on top, rather than your distance prescription
or just plain glass.
The least expensive optical aid is just an eyeglass. The choice of
type and strengths is highly dependent on basic optical needs of the
eye and age (bad word). Presbyopia is the problem which leads most
people to wear reading glasses after age 35 or 40 or so. Here’s a
highly simplified way of trying to solve the problem.
Put on your basic distance glasses, if you don’t wear any you are
blessed. Presumably your vision out the window is now bright and
clear.
If your tools and supplies, scattered on the bench, racks or
shelves, are not in sufficiently clear focus you may want to
consider a correction for arms length. Evaluate the strength for arms
length focus by trying weak reading glasses over the top of your
basic glasses (or by themselves if you don’t wear anything for
distance). Make a note of the strength that helps, it’s likely to be
in the range of +.75 to +1.75.
Now get to the bench-pin, burring, sawing, setting, etc. Put the
arms length reader over your usual glasses and then put a third pair
of readers over it all (really looks weird!). Try various strengths
to find the total that gives you the best focus at the distance you
are accustomed to working. Total up the arms length plus the
additional bench-pin strengths, it may easily be up to +3.50 or even
+5.00.
Now, how do we put this to use? If you wear a
distance glass they will most likely be polycarbonate (a very good
safety material). If you don’t wear a prescription you can get a
reader or non-Rx safety glass over the counter (they will likely also
be polycarbonate). You also can buy “stick-on” bifocal lenses (Optx
20/20 is the usual brand) over the counter. The arms length strength
can be put UPSIDE DOWN on the upper area of which ever eyeglass you
have chosen. On the same basic eyeglass you can install the bench-pin
strength on the bottom area, it will be most useful set rather high,
probably up to the center of your vision. It’s easy to peel them off
to reposition as much as you need.
All this may seem a bit confusing and complicated and also depends
on your specific needs and measurements, but EYE GLASSES CAN NOT HARM
YOU! Experimenting is OK.
On the other hand I’ll be happy to hear from any of you in the hope
of helping to solve your problems.
I’m glad that what I call “super-bifocals” are working out for you.
Many people make them up with over-the-counter reading glasses and
"stick-on" bifocals. I’m still working on an extensive piece on
visual aids for jewelers.
I agree on the use of glass lenses rather than plastic. I had a pair
of polycarbonate lenses for about three days and they scratched
badly. I really had to beg to get my current pair made of glass but
someone finally did it and they don’t scratch. With all the grit and
abrasive dust in a shop you need glass lenses. The “eye guy” will try
to sell you polycarbonate or plastic for “safety” reasons. The real
reason they don’t sell glass much these days is that it is easier to
make plastic lenses and more profitable. I got the straight scoop on
the whole subject from a friend who works for a wholesale lens
grinding lab that supplies many of the local area opticians. I needed
bifocals also and they work well enough after you get used to them. I
intend however to purchase a bench microscope for setting and
engraving etc.