Hello,
If a customer chooses a 8 base curve sunglass and you want to rx it, what would be the best base curve to specify to the lab? Does it depend on the rx, index?
or do you leave it to the labs discretion?
Would appreciate the feedback.
Hello,
If a customer chooses a 8 base curve sunglass and you want to rx it, what would be the best base curve to specify to the lab? Does it depend on the rx, index?
or do you leave it to the labs discretion?
Would appreciate the feedback.
What is the Rx ?
I usually go with what's in the glasses or as close to it as possible, as long as the patient is happy with the base curve in the glasses. I have had trouble with Wiley-X and Liberty frames and too much curvature, both with the cylinder aspect and the lens fit. The lenses have a nasty habit of popping out repeatedly. So our optical has gotten away from fitting those. Unfortunately we still have 10 Liberty frames to unload and then we will go with the flatter sunglasses.
We have found that often 6 bases produce better results.
This question is extremely frame/RX/PD specific. That being said in wrap eyewear I almost always match the curve of the plano lens, or reccomend another frame if that isn't an option.
Nobody should answer this without knowing the Rx, as 2 posters have said. The most important consideration is the back curve, not the front curve (base curve). For example, a -4 ground in an 8 base lens will have approx a -12 back curve. Completely ridiculous. Similarly A + 4 will have a -4 back curve, completely doable. Remember to always compensate for wrap if the rx is over 1 diopter in the horizontal meridian. On that -4 lens, I'd use a 4 base lens and have the bevel follow the back curve, not the front curve, unless you are fitting a horse.
It also depends a lot on how sophisticated your or your lab's edging is. If you do careful shelf bevels you can put in a -10.00 8 base lens and it will be in there as solid as the original plano lens (course I don't recommend that, just sayin a proper bevel can cure all lens fit issues). If you can do this and use good wrap compensation digital lenses you can be pretty free with the 8 base. Higher powers I may drop to 6 base for less distortion, which will usually fit those 8 base wraps with only the slightest flattening of the frame. For a very high power (-8.00) in an 8 base frame I have had it put on a 4 base but my lab custom shelf beveled on the back curve of the lens. Lens fit perfectly and protruded out the front of the frame instead of the back (looks just like the high wrap frames that have the flatter curve inserts like some 3M and Wiley X), and the guy could see great and had wrap sunglasses first time in his life.
Yes it's frame/RX/PD specific, but additionally edging skill dependent. The more edging badassery you have access to the more options you have.
I've fit hundreds if not thousands of -4 or greater wrapped suns with a 90%+ success rate. I always carefully explain to a patient what to expect (fishbowl) at the peripheral.
Only use wrap compensated lenses!!!
Using a stiffer material like trivex or CR39 rather than poly also keeps lenses from warping down the road.
Oh and on the +4 lens, have the bevel follow the front curve; some powers your bevel placement will need to be varied. You can adjust the curve of the bevel some, but remember flattening it will open up the temples.
It also depends a lot on how sophisticated your or your lab's edging is.
Originally Posted by DanLiv
A 10.00 on 8 base curve will look like a lenticular lens and the wearer will see plenty of distortion.
Have you ever done a double groove bevel on a flat edge ?
They are the best looking minus lenses and we used to do lots of them in the 70s and nobody is doing them today.
The shelf bevel capabilities of some edgers these days (with a skilled operator) are unbelievable. You have to have the right lab and be a squeaky wheel to get it done right though.
One day I will have such an edge of my own, for now I have a trusted finishing lab for such specialty wrap work.
RX is OU -5.50
We eat -4.00 8 base sunglasses for lunch. You just need the equipment and the right lens for success. This is actually a very easy job for some and impossible for most. How can that vary so much from office to office and why?
Craig
Because my lab doesn't charge me for step beveling so I let them do these jobs for me and I focus on all the other ones because I can't afford an edger like you have (yet). That is the answer.
Actually you are the one with the answer and that was my question; why do you know what a good lab can be do while most will simply tell a client that it can't be done?
You don't need to own the best equipment but you certainly should be able to utilize what the industry does have to offer and most don't hence the opportunity for the few who are intellectually curious.
Step-bevel with a re-touch can take an hour on the machine and it is brutal but it gets done.
How can something that takes a machine an hour to run be the same price as one that takes that machine 5 minutes? Another example of special optical services not being charged? What a country.
There is just a huge range of knowledge, skills, and equipment not only among opticians but also lab technicians. Price of an unregulated industry. My state has practically zero optical regulation and the ignorance of some "opticians" is abysmal. It's not their fault, they just don't even know what they don't know. They get hired as an unskilled salesperson or technician, trained to do exactly and only what they need to sell the company product, and then their training stops. Electronics salespeople at the box stores might continue learning because they are gadget geeks and like to learn on their own, or car salespeople might be car guys and know a lot more than they have to to sell cars. But there aren't any natural optics geeks, so not enough people in this business have the interest in the field to push their own ability, find out what they don't know, and then figure it out. That makes for a gaping disconnect between salespeople shlepping two pair for $79 in a strip mall, and optical artisans crafting custom eyewear.
Don't know about Craig, but I certainly charge because yes it is a huge PIA (but satisfying) to make those. Big difference between standard polarized suns in a 4 base frame and a wrap compensated digital in an 8 base wrap.
Most labs do charge for this. Lord knows VSP ones do.
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