A patient picked up glasses with the following Rx:
-2.50 -1.75 X 3
-2.25 -0.75 X 172
Add = +2.00
He proceeded to tell me how much he disliked progressives and that he could see at near much better without his glasses on. I must confess that I was quite shocked at that statement but let it pass. He then explained that what he really wanted was a pair of glasses with his distance Rx at the top and nothing at the bottom.
I confirmed that he meant nothing, zero, zip, clear and he replied, “Yes that is exactly what I want but I have never found anyone who could understand what I was talking about, let alone make them for me.”
Well, I love a challenge… and I really did not like hearing that he could not find an optical dispensing professional willing to at least try to help him out. I didn’t tell him I was going to try, I just took the project on to see what I could do.
I had a new frame at home that I donated to the project.
I ordered two pairs of lenses in stock CR-39 one pair distance Rx and one pair 0.00 lenses.
The Rx pair I blocked with the OC about 5 mm high assuring the OC would be above the line I would be creating. The 0.00 pair I blocked on physical center.
I traced the frame on our Santinelli and ran both sets of lenses (the Rx and the plano) as if they were to be mounted in the frame.
I then took surface tape and covered the entire front of each lens. I carefully trimmed the excess away with a razor blade and then made a graph using a PD ruler and a sheet of notebook paper. Using the graph to keep things centered and aligned I lined up the 0.00 lenses and drew a line at 11mm and scribbled out what would be removed (everything ABOVE the line). Then I cut the surface tape with a razor blade along the line and peeled away the tape exposing everything ABOVE the line.
For the Rx lenses I held them together with the 0.00 pair and used the line created by the edge of the tape to draw another reference line and I scribbled out what would be removed (everything BELOW the line). Then I cut the surface tape with a razor blade along the line and peeled away the tape exposing everything that would be removed.
Now --- back to the edger which I ran on “wheel dressing” so I could access the roughing wheel with my bare hands. Reaching in carefully I ground away the unneeded portion of each lens until they just missed the top of the tape. Then I switched to a 1” flat file and hand worked the edge down to the tapeline on each lens.
The flat file provided a nice flat, smooth edge on each lens that, as you can see, created a nice finished looking lens.
Then, thanks to a suggestion from someone over on OptiBoard, instead of trying to use an optical cement I used only the pressure of the eyewire to hold the two halves of the lenses together creating a Franklin style or Executive bifocal lens. I was able to give the patient exactly what he wanted, distance Rx at the top, nothing at the bottom but clear plastic.
This was a fun, two and a half hour, hands-on project that turned out just great. I would encourage every optical dispensing professional to put his or her spare time to use trying a project like this. You never know where it might lead.
For more on finishing lenses see www.OpticianWorks.com.
I am sorry that I did not take pictures as I went along.