To my limited knowledge, one should look at the lens packaging rather than the card given as the cards are generic ones where the shop could give to everyone.
Yes.. look at lens packaging. But not always given by the lab. Some shops practices throwing it away rather than presenting to the customers because the lens packaging sometimes looks very torn and tattered.
1, Reputable stores will not try to cut cost and swith your lens to something else cheaper. Name is always too important to gamble on. how much more can they make by cheating u? and how much more is there to lose for them?
2, Lens thickness varies due to a few reasons:
-Lens Index (1.5 , 1.53, 1.56, 1.6, 1.67, 1.7, 1.74, 1.8 & 1.9)
-Frame's Lens size and shape (longer and bigger shape or more retangular, shows more thickness. Frames like Harry Potters shape minimize the lens thickness.)
3, Prescription for the glasses including Astigmatism.
4, Your own Pupil Distance (determines the position of each individual lens sitting in that particular frame)
Before a salesman recommends any frame, they must at least have choose it based on this 4 caterias. Thats how normally it works. (there are adnormal cases as well

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