Anti reflective coatings are a vaccuum coating , most often done in a dust free environment. The coatings used on alot of lenses bear the names Zeiss, Nikon,and Seiko,same technology as in camera lenses, medical equipment, binoculars, and scopes.
Ultra violet protection is applied to lenses "in office" and comes in a bottle that is either diluted with water or ordered pre diluted for approx 50 bucks a bottle. In a fairly busy office this is changed out weekly, monthly is its not so busy, as it looses its effectivness over time and use.
Polycarbonate lenses have to be coated for scratch resistance in order to get them out of processing, So there is NO need to pay for something that is already there. It is also by its very nature Ultra violet protected , so if you are charged for UV on poly or high index lenses, you have donated to someones Jamaica vacation.
Plastic lenses are manufactured out of a hardened resin plastic CR39. No need to purchase a seperate scratch resistance, as its already built in.
Frame bridge sizes are actually the measurment of the distance between the lenses (DBL) at the narrowest point. While all frames have this measurment printed on them, they all fit different due to frame geometry. A frame with a 15mm bridge, can fit looses than a 18mm bridge depending onthe type of nose pad arrangement, and where the the bridge wire attaches to the eyewires. If you are going to purchase online, increase you success by finding a frame locally , note the size, AND the position of the bridge.
AS for frames, like cars, guns and knives, ther are difference in the quality of the products, you can find $10 metal frames, and $1400 frames. There are differences in the nickle content of the metal, differences in the depth of the electroplating, thisckness ofthewire used, and the quality of the solder holding them together. As most of us can feel the difference between a difference between the knife form the gas station, a custom Knive and those quality production knives in between, by fit and finish, there are the same difference in eyeglass frames. I ask you to visit a store look at the cheaper frames and the more expensive ones. hold them side by side. Yes they are both sparkely and hold lenses but listen to the frame. the cheaper frame will "sound" loose, feel thinner, there will be more slop in the spring. Look at the diameter of the nosepad arms, and for flex frames. the diameter of the wire in the flex parts. There are difference you can feel and see.
Please before I chased out of here let me finish by stating, not all Opticians are out to rip you off, sell crap at high prices and fleece you out of your cash. Alot care, My job is to help you see, with the least difficulty, and greatest chance of success. I don't go to Vegas every weekend, I havent been to Jamaica. I do this cause I love to see kids See leaves on trees for the first time. I trouble shoot vision issues after strokes, diabetes, hypertension for parents and grandparents allowing them to tie there own flies, or simply read again. I fit glasses so you can see without neckstrain at the computer, and while reclining watching tv, by carefully taking measurements.
I buy knives, good ones but am looking for the day when I can drop $500 on a custom job. I am available to answer vision questions, offer advice. I am not promoting anyones shop , I am here selling nothing. As I have learned alot re knives here, I hope to share my experience in return.
Edited for typos as one arm is in a sling, and the other only has 4 working fingers till the swelling goes down
Cheers
I mean, materials and workmanship on frames is about the same level as the Hotwheel cars I used to buy my kids for one lousy buck. :grumpy:
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