Author Topic: What index do you need for strong prescription lenses?  (Read 2402 times)

Chosh

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What index do you need for strong prescription lenses?
« on: December 02, 2015, 05:08:20 PM »
Hey forum, posting a "what index should I pick" question where the answer isn't going to be VTSAX :)

I wear eyeglasses now and then and the last pair I owned just broke.  I'm looking at buying a new pair online (likely zenni) and it looks like if I went with the recommended lenses, the lenses themselves would be ~80+% of the cost!  How important are high index of refraction lenses if you have a strong prescription?  Mine is -8.0 in both eyes.

Thanks for the help!

johnny847

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Re: What index do you need for strong prescription lenses?
« Reply #1 on: December 02, 2015, 05:20:24 PM »
I have a -8 and -7.75, so I know your pain.

I have high index polycarbonate lenses, and I would highly recommend them, especially if you want to use frames that will use big lenses. With a low index lens, it needs to be thicker to refract light at the necessary angle to correct your vision. With a thick enough lens, you get weird distortions near the edges of the lens (where it will be thickest). I've noticed this in my sports goggles, which have the same index as my normal glasses, but have physically bigger lenses. I get a weird vertigo feeling whenever I put them on (thankfully, it's pretty mild, and I don't wear my sports goggles often).

Valetta

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Re: What index do you need for strong prescription lenses?
« Reply #2 on: December 02, 2015, 06:20:38 PM »
I think the high index lenses are critical. I wear -11 in glasses, -9.5 in contacts. For me, even with high index I get distortion around edges because my prescription is so strong. I can't imagine what it would be in regular lenses, I don't think they would be wearable at all.

It's worth the cost so I would just pay it.

Meowmalade

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Re: What index do you need for strong prescription lenses?
« Reply #3 on: December 02, 2015, 06:43:09 PM »
Before I got laser surgery I was -9 (contacts) in both eyes.  I definitely recommend getting the thinnest lenses possible, and my optometrist also recommended getting small frames, since the wider they are, the thicker the ends get.

arebelspy

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Re: What index do you need for strong prescription lenses?
« Reply #4 on: December 03, 2015, 01:24:49 AM »
I have -9.5 in both and don't bother with the extra thin at Zenni. The wife has -9/-10.5 and doesn't bother with it.

It is a bit more expensive, because at that range they add on a mandatory extra charge, but beyond that we just pick the cheapest option, and have done so multiple times, and it's worked out great.

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partgypsy

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Re: What index do you need for strong prescription lenses?
« Reply #5 on: December 03, 2015, 10:43:39 AM »
I also have a high prescription. The high refractive lense adds what - $30? to the cost? To me worth it for being more comfortable, less heavy and less distortion. My prescription hasn't changed much so I can go years with the same glasses. To me it is worth it. You still pay with Zenni a fraction what you would at a regular glasses place.

Chosh

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Re: What index do you need for strong prescription lenses?
« Reply #6 on: December 04, 2015, 12:55:48 PM »
Thanks everyone for the feedback!

The only factor that I'm moderately concerned with is distortion. I can't imagine glasses heavy enough that comfort would actually be an issue, and I've not seen glasses thick enough to be a cosmetic issue outside of a cartoon :)

After seeing your feedback though, the obvious approach seems to be to get a pair of cheap glasses and see whether they bother me or not.  If not, great!  If I do have issues like some of you seem to, then I can always go with the fancier lenses.