Types of optical lenses (CR-39, high index, polycarbonate etc)

[SpatiallyAware]

I'd really like some real-world advice from someone that really knows about these lenses.

My optometrist (Costco for everything) strongly recommends the high index lenses since I'm -4.00 in each eye. However, I notice fairly serious 'chromatic aberration' with my other pair of high index lenses.

It is particularly problematic with computer stuff.. With a 24" LCD I have to turn my head to look directly at things to keep things in focus with these high index lenses. I also have a pair of CR-39 glasses and they seem to have much much less of an issue with distortion etc.

I explained these problems during my last eye exam and she recommended 'polycarbonate' which is thicker than CR-39 but less distortion than high index.. However, these somehow seem to have slightly worse chromatic aberration and distortion that the high index lenses!



..........So then I compare all three side by side and realize that the CR-39 is only maybe 5-10% thicker than the others!

So what exactly is the benefit of high index? Is it only thickness? I'm confused as to why the high index is so much more expensive with seemingly no benefit.. Every optometrist person I talk to seems to shy away from CR-39, although the optical guy that fits my frames says he prefers CR-39 and hinted that these high index lenses are more or less scammish and not really needed unless you have huge frames or really horrible vision.

Note that all of my frames are about the same size and are wire-rim (I think.. Basically there's a metal frame on top with thick plastic string holding in the lenses)


Thoughts?

 

[DrPizza]

I agree with you - ditto on the recommendation. It turns out "what are we talking about in terms of how much heavier they are?" "A gram or two."

I cannot stand high index lenses because of the chromic aberration. Looking straight forward, no problem. But, I have excellent peripheral vision & it constantly annoys me. Plus, there are a lot of situations where I am not looking perfectly forward through my lenses, i.e. hunting. They told me I'd get used to them; I returned them in a week & have refused them ever since.

 

[Daedalus685]

I find the aberration a pain in the ass on my glasses (traffic lights, the odd blue LCD clock... shudder), the lenses really are much thinner and easier to wear (at my prescription anyway). Being smaller means they can fit in more frames too, stylish frames often have heavy restrictions on how large a lens can be.

At -10 and -10.5 I'm kind of stuck. At -4 you have no reason to need to sacrifice optical quality for ease of wearing though. They are generally much more expensive as well.. I find they scratch much easier than the heavier material too.

They are for those of us who with some of the thicker materials cant actually fit them on our faces...

 

[sdifox]

I am at -6 and I am on high index. I also got astigmatism... No chromic aberration for me though.

 

[BoomerD]

I find the aberration a pain in the ass on my glasses (traffic lights, the odd blue LCD clock... shudder), the lenses really are much thinner and easier to wear (at my prescription anyway). Being smaller means they can fit in more frames too, stylish frames often have heavy restrictions on how large a lens can be.

At -10 and -10.5 I'm kind of stuck. At -4 you have no reason to need to sacrifice optical quality for ease of wearing though. They are generally much more expensive as well.. I find they scratch much easier than the heavier material too.

They are for those of us who with some of the thicker materials cant actually fit them on our faces...

-10 and -10.5?
Jeezus motherfucking kryst...you're blind!!11!!

I feel blind because I'm at a +3.5!

 

[SpatiallyAware]

-10.00 yikes..


Ok, it sounds like high index really only seems to affect thickness once you hit about -6.00, even though the 'examples' of high index makes it out as though there's a significant difference in thickness even though I'm really not seeing it.


So.. I'm going to get these poly lenses swapped out for CR-39...

 

[bhanson]

Wtf.

I'm -0.5/-1.0 and I feel blind. Sitting in the back of the room and reading any text at the front is impossible. Sitting at the front of the room and reading text is only possible while squinting. I cannot legally drive without corrective lenses.

Yes, I can function, as long as it doesn't involve any driving or reading.

I pity you all. D:

 

[sdifox]

Wtf.

I'm -0.5/-1.0 and I feel blind. Sitting in the back of the room and reading any text at the front is impossible. Sitting at the front of the room and reading text is only possible while squinting. I cannot legally drive without corrective lenses.

Yes, I can function, as long as it doesn't involve any driving or reading.

I pity you all. D:

I guess corrective eye-wear never made it to your neck of the woods? How about surgery?

 

[bhanson]

I guess corrective eye-wear never made it to your neck of the woods? How about surgery?

Inferring fail.

 

[thecoolnessrune]

I have high index lenses milled down to a perfect spec for my eyes and I don't notice any chromatic aberration on this pair. They do smudge easier though.. My lenses are -4.28 adjusted for the astigmatism. They have a few "additions" such as the transitions layer (embedded, not coated) as well as an Anti-Reflective coating that doubles as an anti-scratch coating.

These lenses are a very high index (1.74) and have a *ton* of chromatic aberration when looked *at* (If I take my glass off and look at the front of the lenses, everything reflecting off is rainbow colored). However, I myself never see any aberration when wearing them.

They were stupidly expensive lenses, but I've really enjoyed them.

 

[SpatiallyAware]

I'm fairly sure that all high index lenses have chromatic aberration unless you have tiny frames.

It's generally not all that bothersome except for 24" LCDs. Turn your head to the left or right so that you're looking out of the outside edge of the lens and you'll see either a red or blue 'fringe' on any vertical edge. I have really good peripheral vision and pick up on a lot of stuff out of the corner of my eyes and it's definitely an issue for me..

This page has some examples, try looking out of the outside edge of your lens to see what I'm talking about:
http://toothwalker.org/optics/chromatic.html


Ultimately I just have to deal with the extra weight and apparent thickness (which really isn't all that much apparently until you're above a -6.00) of CR-39 because high index just isn't clear enough for day-to-day usage for me.

He did mention that they have a glass product that is supposed to have excellent optics although they're the clear/dark transitions and I don't want those.. Plus they have to have a full frame due to the weight

Edit:

thecoolnessrune: that's not chromatic aberration, that's the rainbow of your AR coatings.

 

[thecoolnessrune]

I read your link and agree with that. I threw up a white background on my LCD and tried to look at it peripherally and didn't notice any discernible aberrations on my lenses. My lenses aren't that big though and I'm certain that has quite a bit to do with it. I wear my glasses close and therefore don't need that much lens to cover my entire usable vision area. I can still detect motion peripherally just fine and I figure if its that important to be able to notice the finest details I should probably be looking at it directly anyways so that I get proper depth perception (hunting, etc.)