glasses lens type? (aka: zenni optical questions)

Ika · 01-06-2011, 07:46 PM

So I'm about to order from Zenni for the first time, and I'm having a little trouble making a decision. Should I get the 1.50 Standard index, 1.57 Mid-index, or polycarbonate choice (+$9) worth it, for 1.59?

What's the difference between the lens indices? Is there any difference other than physical size/shape of the lens (as seen in their comparison picture)? The way I understand it, from optics, higher indices of refraction allow for less curvature, because the glasses "bend" light more - but with smaller frames doesn't this cause eye strain or fatigue or something?

If it helps, these glasses will primarily be used as backups to contacts, so generally indoor usage and computer usage only. Ideally I'd like something that causes the least amount of computer screen strain as possible, since it can be an issue for me when I wear glasses for extended periods of time.
TIA

Imp · 01-06-2011, 08:27 PM

If I recall correctly, the higher the index, the thinner the lens. Mainly for aesthetics, you'll look like a super nerd with low index and a high prescription.

But you really don't need low index unless you're as blind as I am, or worse. My eyes are -6.00, and the Kodak high index lenses I have (for $250; I wanted to support a small local store

) are only as thick as the frames (3-4mm). I use to use mid-index and they weren's so bad.

If you're 1.59, not remotely worth it, especially for back-up use.

Ika · 01-06-2011, 08:45 PM

Quote:

Originally Posted by Imp

If I recall correctly, the higher the index, the thinner the lens. Mainly for aesthetics, you'll look like a super nerd with low index and a high prescription.

But you really don't need low index unless you're as blind as I am, or worse. My eyes are -6.00, and the Kodak high index lenses I have (for $250; I wanted to support a small local store

) are only as thick as the frames (3-4mm). I use to use mid-index and they weren's so bad.

If you're 1.59, not remotely worth it, especially for back-up use.

Oh, I think the numbers are referring to Zenni's index of refraction for the material they use. My prescription is -3.5/-2.25, so I'm pretty moderately nearsighted.

DrPizza · 01-06-2011, 10:27 PM

As far as the difference in thickness, it depends on your prescription. Off the top of my head, I believe high index are advertised as "up to 42% thinner." But, for less corrective lenses, the difference is much less than that. Another problem with high index lenses is chromic aberration - which is the reason for some blurriness. In the case of the pair I had at one brief point, the farther from the center of the lens I was looking, the more blurry the object would appear. High index lenses are also slightly higher density, so it's not a perfect savings on the weight. High index lenses allow a lower percentage of the light through (80-something instead of 92ish according to one site I was on recently) - this is because glare is a much bigger problem with high index lenses. If you get them, then getting the anti-glare coating is a good idea.

That said, for some people, they're awesome; especially those with a strong prescription (according to that website I was on - either yesterday or this morning.) Also, the curvature can be changed on the lenses to help lessen the effects of the chromic aberration. And, as said, some people would prefer them simply because of aesthetic reasons.

qliveur · 01-06-2011, 10:35 PM

I paid the extra $9 for the polycarbonate because it's more impact and scratch resistant than the regular lenses, and for $5 the anti-glare coating is pretty much a no-brainer. Even with titanium frames the glasses were still only ~$65 shipped.

borisvodofsky · 01-06-2011, 11:56 PM

I bought two pairs from zenni optical last year, same glasses, one with 1.67 index and one with 1.59,

Aesthetically they are of the EXACT same thickness...

I'm inclined to believe that they Do in fact use the same material since the customer would have no ability to test the lenses.

WaTaGuMp · 01-07-2011, 12:00 AM

I bought the 1.59, total cost for single vision at the time with delivery $17.80. They are every bit as good as my $140.00 ones from Costco.

qliveur · 01-07-2011, 12:04 AM

Quote:

Originally Posted by tp4tissue

I bought two pairs from zenni optical last year, same glasses, one with 1.67 index and one with 1.59,

Aesthetically they are of the EXACT same thickness...

I'm inclined to believe that they Do in fact use the same material since the customer would have no ability to test the lenses.

Quoted for bullshit.

DrPizza · 01-07-2011, 01:49 PM

Quote:

Originally Posted by qliveur

Quoted for bullshit.

He was complaining that they sent his last pair of glasses to the wrong address. He thought that someone there wrote the address on the box, rather than using a shipping label printed out from the information that HE typed in. I'm guessing that he simply has trouble filling out forms correctly.