How to tell if my glasses have high index lenses?!
Question: How to tell if my glasses have high index lenses?
I went back to my doctor to ask if they are truly high index because I spent so much on them. He looked at the order form and said that they were. He didn't even look at the lens. So my question is, can anyone tell me how to tell if my glasses are actually high index by looking at the lenses itself. My last pair of glasses were also high index, but much thinner! My prescription only increased two tenths of a point in astigmatism, but everything else was the same.
Answers:
Best Answer - Chosen by Voters
If you chose a larger frame, it could cause your lenses to be thicker even if the index was the same. Different materials do sound different but I would be hard pressed to tell you if a lens is 1.60 or 1.74 by thumping it or dropping it. You can tell to some extent by using a device called a lens clock that measures the curvature of the lens. I suppose there are formulas that would tell you based on the measure of the front curve and the back curve, the index could be calculated very exactly. Most optical places do not do this on a regular basis. Getting the correct index seems to be very much a matter of trust. The lab trusts the manufacturer of the lens to label the lenses correctly. The doctor trusts the lab and you trust the doctor. That is why it was not unusual for him to just check his paperwork to see if you got high index.
optometrist
They look and sound different when tapped with something metal...but that doesn't help you much.
Drop in to any optical store and just show them to the optician , they will tell you right away.
Optician