I am trying to show a patient how thick their patients +31.00 lens would be without using a lenticular lens. What formula can I us to estimate center lens thickness and edge thickness? I tries to explain to the best of my ability why that would be a dumb idea but I was not successful. I am hoping somehow if I am able to show them they will understand. I used the calculator on opticampus but I don't thick accurate. Thanks
You might hand them a clear "boulder" marble, actually a "toe breaker" size would be about right:
http://www.ebay.com/itm/Vintage-Larg...-/201531527226
Last edited by Dr. Bill Stacy; 03-03-2016 at 11:33 AM.
The calculator only goes up to the mid to upper twenties, depending on the lens size. One idea is to show them what size frame they'll need if you use a single cut or full-field lens, something like a 34mm eye size and a bridge wide enough to match the IPD, 26mm or so! Aire-O-Lite has SV BCs put to +50 D.Originally Posted by Mizikal
http://www.aire-o-lite-optical.com
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Robert, are you sure they make 50D BC lenses (not 50mm bowls)? Back in the 70's when I was a lab supervisor at Universal Ophthalmic Lab, we had our own CR39 casting ability (one of the only wholesale labs that had that capability.) We made 40D lenticular "buttons". The size of the 40D was about the size of a large marble. I can't imagine a 50D lens!
I've never seen one, but I did order a +20 D for low vision last year.
You were casting in the 70's? So much skill and talent here on Optiboard.
Use the link from the above post and click on 'products'. Here's a cut & paste of the SV product.
65m/m Single Vision Lenticulars
Semi-Finished
Material: CR-39*
Base Curves: 8.00, 10.00, 12.00, 14.00, 16.00, 18.00, 20.00, 22.00, 25.00 Field Size (Bowl) 34m/m or 38m/m
28.00, 30.00 (Field size 34m/m)
34.00 (Field size 27% m/m) 38.00 (Field size 25m/m) 42.00 (Field size 21 m/m)
46.00 (Field size 20m/m) 50.00 (Field size 20m/m)
65m/m Extra Thick 15m/m Edge Available
65m/m Extra Thick 22m/m Edge Available
32.00 Base, 36.00 Base, 40.00 Base, 44.00 Base, 48.00 Base Extra Special Bases
Material: CR-39* Plastic Specific Gravity: 1.32
Index of Refraction: 1.498 Single Vision Lenticular
Abbe Value: 58 65m/m Blanks
34m/m or Smaller
Note:* Note:**
Lens Actual Nominal Actual Back Carrier Seg Bowl
Style Size Curve Curve Curve Curve C.T. E.T. Inset Size
S.V. 65m/m 10.00 ** 2.75 6.25 16.6 11.5 S.V. 34m/m
S.V. 65m/m 12.00 ** 2.75 6.25 17.0 11.5 S.V. 34m/m
S.V. 65m/m 14.00 ** 2.75 6.25 18.5 11.5 S.V. 34m/m
S.V. 65m/m 16.00 ** 2.75 6.25 19.0 11.5 S.V. 34m/m
S.V. 65m/m 18.00 ** 6.25 6.25 15.5 11.5 S.V. 34m/m
S.V. 65m/m 20.00 ** 6.25 6.25 16.5 11.5 S.V. 34m/m
S.V. 65m/m 22.00 ** 6.25 6.25 16.6 11.5 S.V. 34m/m
S.V. 65m/m 25.00 ** 6.25 6.25 18.2 11.5 S.V. 34m/m
S.V. 65m/m 28.00 ** 2.75 2.00 17.6 11.5 S.V. 34m/m
S.V. 65m/m 30.00 ** 2.75 2.00 18.0 11.5 S.V. 34m/m
S.V. 65m/m *34.00 ** 2.75 2.00 14.4 11.5 S.V. 27m/m
S.V. 65m/m *38.00 ** 2.75 2.00 14.6 11.5 S.V. 25m/m
S.V. 65m/m *42.00 ** 2.75 2.00 13.6 11.5 S.V. 22m/m
S.V. 65m/m *46.00 ** 2.75 2.00 13.5 11.5 S.V. 21m/m
S.V. 65m/m *50.00 ** 2.75 2.00 14.5 11.5 S.V. 20m/m
Note:* 34.00 Base and Above have BOWL SIZE REDUCTION. Note:** TRUE BASE CURVE specified on each lens you receive.
Normally .25 to .75 diopter stronger than Nominal CURVE.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Looks like the +42 has a bowl 22mm in size...About the size of a large marble. We cast a ton of these for overseas sales. I always wondered why anyone would need them, let alone in the quantity we cast them!
You need one of these. Chose the third image.
http://www.optikam.com/products/optikampad/lens-demos/
Looks nice but for what the OP is looking for, is it even set up to show Rxs that high? A few systems I have seen usually stop around + or - 8 or 9 diopters
Nothing in all the world is more dangerous than sincere ignorance and conscientious stupidity
I think Robert answered the original OP with his post (#3). I don't think you can get a full field blank higher than a +20 so that leaves you with only lenticulars to get a high enough BC to make a +31. ( And only in CR39 at that.) As he stated, you'd need a frame with a max 34mm eye size with zero decentration to cut out full field. ( Don't use a bi-convex design either!!)
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