have to change my glasses... and they say -6 and -5 lenses will be too thick, is!

Best Answer - Chosen by Voters

At that power, it certainly is worth it , and you will see better also with the thinner lenses.

The hi-index ( thin lenses ) will be at least 40% thinner than a regular lens, so THAT is a big difference.

Any powers over - 3.00 are very worthwhile to get the thinner lenses.

Optician

Your minus lenses are going to be shaped like this )( if you look from the side and plus lenses would look like this ()

The problem with high powered minus lenses is that the edges of the lenses are very thick. Plus lenses aren't as much of a problem since they thin out as you get closer to the edges, where minus lenses actually get thicker at the edges.

Lenses are able to do their job, because light is bent when it enters glass, plastic, or any material that is more or less optically dense than air. Two things control how much the light is bent.

1) The more curved the lens is on each side, the more it will bend light. So || bends light less than )( or ()
2) The higher the "index" or optical density of the lens material, the more the light will be bent

So, you can have a more powerful lens with the exact same shape and size if you increase the index. This is what they are trying to sell you. A minus 5 or 6 lens is going to be thin at the center and get thicker as you move out from the center - thick at the edges - if you just used glass, plastic, or polycarbonate. They have come up with newer high index materials that can bend the light more even when the lenses are less curved (which makes them thinner at the edges and weigh less). Of course, these lenses are more expensive.

If you don't care about not having that coke bottle look to your glasses, then don't worry about it. If you do care, you have a few options.
1) buy the higher index lenses
2) you can get contacts
3) You can have refractive surgery (LASIK, etc) if your prescription has stayed stable for long enough
4) You can get smaller frames - since minus lenses get thicker as you move out from the center, if you get small frames, then the glass won't go out very far from the center and won't get as thick. Of course a smaller area of your visual field will get the benefit of the glasses with this option.

Ophthalmologist

It is worth it to get thinner lenes with that rx, but if you can't afford them, or wear contacts most the time, then you could go with the stardard CR39 plastic. The polycarbanate is what they are trying to sell you are thinner and lighter. If you decide to go with the standard cr39 plastic lenes, then I would suggest going with a smaller frame, because it will shave off more of that thicker edge, and also plastic frames hide that thicker edge also. Good luck with your choice.

glasses sales person

Absolutely too thick. Anything more than a -4 usually calls for high index or "hilite" lenses. You can get them pretty cheap at www.replacementlensexpress.com. Go on their site to check out the prices, but then e-mail the optician and get his opinion as to which type of index you need, and how much they will be. I used them once and thought that the prices were really reasonable and the quality and turn-around time were great too.

www.replacementlensexpress.com

I have this sort of perscription. it used to be that the thinner lenses weren't available. My glasses then were very heavy and I used to get rubbing on my nose and behind my ears. The new hi-index lenses are unbelievably better - when I first got them I couldn't believe they were in my perscription and have made a huge difference to me. The other thing to do is make sure you get frames which need as small lenses as possible as most of the weight is in the outside edge of the glasses.

Hi-index lenses also look a lot better