What happens if you use High index lenses on a low prescription?

Question

I will get a new pair of progressives. My nearsightendess prescription is -2.75 and reading is +4ish. The side of the lens is really thin but the top and bottom are a tiny bit thick. If I get high index 1.67 what would happen to the sides since it doesn't seem that they can get thinner by a lot, and what would happen to the bottom and top since that definitly does have room for improvement? Is it possible to only make the top and bottom thinner and leave the thinness on the sides how it is?

Answer 1

First, a 1.67 is way too high for a prescription like that. A 1.67 is not recommended under -6.00

The optics wouldn't be good with an index that high in your prescription.

A 1.6 would be as high as you should go..there would be no difference in the thickness in that power anyway between the 1.6 and the 1.67

Something is wrong with your numbers too...a -2.75 would produce the thickness on the outer edges, not at top and bottom. You must have a fairly high astigmatism correction in there also for it to make the top and bottom thick.

Anyway...a 1.6 or any high index lens will make it thinner all over because the center starts out thinner...usually 1.0 mm at center.

The difference between the regular plastic lens and a 1.6 is close to 40% thinner...so the top and bottom will be thinner, yes, but the outer edges will be alright still.

But as I said, there has to be something about your prescription that you haven't included...you say the reading is + 4ish...that only confuses it more....lol

I have a feeling that 4.00 you saw somewhere is a correction for astigmatism, that would explain the thickness on top and bottom.

So, without seeing your actual prescription, and going just by the - 2.75 you say it is...then forget about 1.67...that's no good for you....1.6 would be perfect.

Answer 2

you eye ball will shrink as you a re not using the right prescription .. you will get ******** syndrome too  

Answer 3

i do not no