Which refraction index should I get for my glasses?

Question

I just got a new glasses prescription:

OD -5.75 -0.75 x130

OS -6.00 -0.25 x040

For the lenses, I know I'm getting CR39 plastic because it's more durable and cheaper than glass. I just can't decide on which refraction index to get.

I'm given 1.57, 1.61, and 1.67. The higher the number, the thinner and more costly the lenses will be.

Here's my dilemma: if I get 1.57, I'm worried that my glasses will be too thick and I'll look lame. On the other hand, if I get 1.67, I don't want it to look like my glasses are fake because they're too thin. I also don't have a whole lot of money right now. (Poor college student, etc)

Does anybody wear anything in the -6 diopters range? What refraction index do you have? Can anybody recommend anything for me?

Answer 1

The 1.61 can do a very nice job if you are looking to save bucks, compared to 1.67

Your frame choice can make a lot of difference. Be sure to get something as small as possible that still fits you, and that your pupils are on, or  very close to being on center of the lenses..

There is also the polycabonate lenses which are 1.58 index...very light and as thin as the 1.61...but many people find that the optics of polycarb just aren't as crisp and clear as the 1.61 hi-index plastic.

Answer 2

You can use this site to calculate the thickness for each refraction index, and then decide which you want: http://www.opticampus.com/tools/thicknes...

Answer 3

Just so you know. Cr-39 IS the 1.57. The rest are just a higher index of plastic, but not called CR-39. I have a -6.75 and I have been an optician for 27 years. I use one of two. I either use the 1.67 or Polycarbonate.  Polycarbonate is technically a higher index material and is thinner and lighter weight. Most of the 1.67 matterials are aspheric automatically, but with the Cr 39 (regular plastic) the polycarb, and the other indices 1.60 on up, you can get these in what is called an aspheric lense, which gives you better clarity, less minification, and a thinner flatter lense. To get the best of all worlds I would reccoment this"

First...get a frame that is plastic and has what we call little or no decentration. This means that your eye sits in the dead center of the lense. We do not want the fram squshing your head though, so make sure it fits you head well still. Second, get the polycarbonate with an aspheric design, and ask for an AR coating as well. This will usually (I said usually..) be more cost effective than getting the other fancier lenses. The deal is that you do get what you pay for in most instances with yoru RX. To get the most for your money I would call around and ask about pricing and scratch and breakage warranties. Also, make sure you are working with an experienced optician so that you get the right measurements as well.  In my office here are the prices you would be looking at:

Frames range from $90 to $600 and everywhere in between. All my frames have a 2 year breakage warranty. No copays, you do not pay for my warranty. It is in there.

Plain CR 39 (No scratch warranties, no uv, nothing.) $70

Polycarbonate (Scratch coat, UV, 1 year warranty against scratching)                                                                         $122

Aspheric design                                                                 $20

Anti Reflective coating:

          Regular (Nice optics, tough,1 year warranty)   $65

          Premium (Fantastic optics, very tough, 2 year warranty) $105

So, I would reccomend the Poly aspheric ($122 +20= $142) and a good frame. If you can swing the Ar coatings do so, you will love it on a high minus correction as it clears up night time driving glare, computer screen glare, and overhead lighting glare.  Do not worry about your glasses looking too thin. Most people do not worry about that.  Good luck!