CurtPalme.com Home Theater Forum

[CasetheCorvetteman]

I do sometimes when im not wearing contact lens.

Has anyone else noticed that their glasses have an effect on convergence? Mine do, perfectly fine through the middle of the lens, but off to the sides it separates red and blue to the point i can look at a white cross hatch patern through the edges ( as in looking sideways ) and see 3 colours separated completely.

This is something i see on everything i look at, its not a screen image related thing. Not seen at all with my contact lens.

[km987654]

Is that a problem with your lenses?

I can't say I see that.

[CasetheCorvetteman]

Id say so yeah, i dont recall seeing it before, but its been 10 years since id had glasses i used, i always wore contacts. I see much sharper with my glasses, im only 20-20 with my contacts due to astigmatism in one eye that my contact lens dont correct.

I trialed some astig correcting contacts about 5 years ago, sharp as a tack, but after 2-3 hours my eyes were incredibly dry and the contacts had to be removed due to the servere discomfort they caused. I regularly wear contacts for 18 or more hours a day.

The glasses i got i rarely wear outside of home, but they were $59 Spec savers ones, ive asked them about it and they seem to have no idea. Two of them actually said it wasnt possible.

Watching a movie or playing games its never an issue, im back far enough that its no concern.

[barclay66]

Hi,

this might be able to explain it: http://en.wikipedia.org/wiki/Chromatic_aberration

Regards,
barclay66

[CasetheCorvetteman]

Thanks mate yes, that is exactly it.

[Spanky Ham]

Holy Crap, Case!!! Your eyes are just like mine. I was about to start a thread on this. One of the reasons I drove this trip was to go see my brother's eye doctor. This was my exam in probably 20 years. He diagnosed me with an astigmatism in both eyes. The right eye is worse. I was going to get glasses, but he was able to give me contacts right there. I don't know the brand, but the right eye bugged the sh$t out of me. I decided to leave them in overnight and now they feel ok. I will ask the brand when I go back.

I went to this eye doctor for two reasons. One my brother is a doctor, so I figured he had vetted him pretty well. Two and more importantly, he has this diagnostic tool called optomap. It takes a 3-D picture of your eye and allows him to see everything going on in your eye.
http://www.optos.com/en-US/Products/Retinal-imaging-products/

[kal]

Definitely CA.

You see it a lot in photography and video/movies too from (some) lenses used in cameras.

Kal

[kal]

Definitely CA.

You see it a lot in photography and video/movies too from (some) lenses used in cameras.

Kal

[CIR Engineering]

[Spanky Ham]

Craig,
Something I never knew that this doctor told me is that your vision will deteriorate till around 55 to 60 and then it levels off till you die. So, at least it doesn't continue to get bad in old age.

[CasetheCorvetteman]

Spanky first, we have a very simular sort of thing here in the past couple years where they take a 3D pic of eash eye, blinding flash!! The contacts i have worn for a few years are a monthly replaced daily use type, remove and soak overnight in Optifree Replenish. The astig correcting contacts had a broader diameter which is very likely what caused the issue for me, and it was absolutely unbearable.

Craig, that is correct in my case, zero aberration with the contact lens. One eye has a scar that affects it's vision, however both eyes are quite steady at a -2.75 prescribed contact lens, ive been on them a number of years now.

You really need to try the contacts and see what they do for you, Spanky will probably agree they are quite tricky to deal with early on in terms of insert and remove, in my case it take me maybe 5 days til i would not even notice them in my eyes after 5 minutes or so. Im looking at near 15 years of contact lens use now so i can insert and remove without a mirror if need be

Find a place that will give you a trial on various types and brands, some will suit some people better than others, but absolutely give it a go mate

Another note-worthy point ill add, if i wear polarised sunglasses over my contacts it sharpens things up abit too, and same effect worn over my glasses, however my previous glasses were polarised themselves, making one side total blackout through the sunglasses.

[Spanky Ham]

I just took mine out after leaving them in overnight. They were bothering the crap out of me and I decided if they were fine in the morning then I would keep trying to live with them. I woke up to not even feeling them. Your right that I am going to have to experiment, as I was just telling my brother that my left eye was fine but my right eye (the bad one) didn't seem any better.

[garyfritz]

Spanky, check with your eye doc to see if your contacts are OK to be left in overnight. If they aren't, they can cause MAJOR problems.

Case, that color separation is indeed chromatic aberration. I've found that it's much worse in the high-index plastic lenses they like to use these days, especially if you have a strong prescription. The high-index plastic gives you thinner/lighter lenses, and a bit better UV protection. But if you have a strong prescription, the high-index plastic also causes worse CA and other optical problems, see e.g. wikipedia.

With high-index lenses, if I look at a magenta line on a black background on my computer monitor, it looks OK at the center of the lens. But as I move away from the center, the line diverges into two separate blue and red lines! Not good. It's most noticeable with magenta-on-black, but it also means EVERYthing gets blurry away from the center, because the blue/red are "out of convergence." I found it also causes a lot of eyestrain.

I always specify CR39 plastic for my lenses. It's a lower-index plastic, so the lenses are a bit thicker, but not really that noticeable. But the improvement in CA is VERY noticeable. (I wonder what index of plastic they use in the contacts?)

[CasetheCorvetteman]

Contacts are made of of a very large % saline, in some cases more than 50% saline. They are very soft and will dehydrate extremely quickly if left out of your eyes or out of solution too long.

[garyfritz]

That's right, I forget they don't use the old-skool plastic contacts much any more. (My contact-wearing days were before they invented soft contacts.) Yes, if you take them out, you definitely need to store them properly in solution.

CR39 has an index of refraction of just about 1.5, glass is about 1.523. High-index plastics range from about 1.55 to 1.70. Saline solutions are about 1.33, and this NIH study says in-vivo soft contacts are about 1.40-1.42. So the contacts have an even lower index of refraction than CR39. Maybe that's why you don't see the CA problems with contacts.

But if you need glasses, and you're having trouble with CA, definitely tell them to use CR39. As far as I know it's the lowest-index plastic commonly used for glasses. This article lists some of the other disadvantages of high-index plastic: they have significantly higher reflectance than lower index lenses. This higher reflectance creates increased veiling glare under ordinary lighting and also creates annoying ghost images when bright light sources are introduced into an environment of generally low illumination (e.g. oncoming headlights during night driving or candles in a darkened restaurant). Or high-contrast images in a dark HT.

[CIR Engineering]

[stefuel]

I reported this years ago. I think over at AVS before this forum. It drove me mental and is why I am the way I am today
You can converge it with your glasses on and it will look fine then take them off and clearly see it's out of alignment. Then do it without glasses and the sam thing when you put them back on. I finally came to the conclusion that it was some sort of refraction caused by my progressive lenses as I could also see it on white objects while driving. Put on your glasses and stare at the edge of a well lit white sheet of paper.

[garyfritz]

That's all it took, Chip?? Musta been a short drive.

For me, the glasses on/off wasn't the issue. For one thing, if I take my glasses off, I can't tell if it's converged or not. I can see the picture but no details. But also, with my glasses (non-progressive, progressives may act differently) the CA was OK in the center, not at the edges. So it depended on where I was looking. The image could be perfectly converged and if I looked at any area through the center, it was fine. But move my eyes without turning my head and the convergence is whacked. Sounds like that's what Craig is seeing too.

Craig, glad I could help! My God, with your job you've been using high-index plastic?? It must be driving you nuts! Careful, or you'll end up like Chip!! How strong is your prescription?

[CasetheCorvetteman]

Same for me Gary, i have to move to directly infront of the screen if using my glasses to converge, or stand way back.

[mx83toy]

my eyes are sh*t!!! i use binoculars and lots of squinting ive got some pretty bad stig issues...

[CasetheCorvetteman]

I use binoculars for focus.