Chromatic Abberration in eyeball

A couple of times in the past few months, but only a couple, I have noticed a distinct chromatic abberation, like looking through a cheap achro, when looking at a bright object (the moon last night, and Jupiter a month ago). There is a distinct violet glow on one side and not so obvious yellowish on the other.

Is it possible to get Chromatic abberration in a set of human eyeballs?

And why do I not have it always?

Or is it an atmospheric thing?

I have never noticed it before.

And just to make clear about my question, this was without any optical device.

And just to make it on topic in the Equipment Forum, these were with my standard Eyeball Set (generally matched set of two), Level 1.0, release version 1.0, as issued on September 2 1949. These are bluish eyes, if that makes a difference.

Alex

What scope?

On-axis or off-axis?

I've sometimes noted odd chromatic effects if I am tired or careless and my eye is not properly aligned with the eyepiece's exit pupil. They go away when I take care about the placement of my eye.

Clear skies, Alan

Hi Alex

I'm ignorant and hopefully not being alarmist, but a cataract in the early stages might make that effect. Since it is extremely unlikely you would have identical cataracts in both eyes, then if you see the identical effect in both eyes, it probably would not be a cataract.

Even if it is an early cataract, its no big deal. The surgery nowadays is not much worse or riskier than getting a tooth filled. You wait till the thing is 'ripe' then have it removed. I had em in both eyes, and see better than ever after the operations. The replacement lenses are much better than nature's standard equipment (grin).

Maybe other eye issues could cause it. Do you see an opthalmologist yearly?

Really bright stars, low in the sky, sometimes look like speck-sized disco color wheels to my eye, but that isn't as you describe.

I have noticed similar effect at times, but
I really have to try to see it. My interpretation
is that cornea gets slightly wedged depending
on degree of tiredness / squinting / hours
vertical vs. horizontal / etc. I suppose if
you had otherwise exceptionally excellent vision,
it might be more noticeable. For me, it is
usually lost in ths slight blur of other aberrations.

I can also make a similar effect by looking through
edge of eyeglasses, instead of the center. But that
is trivial chromatic aberration, and easy to
understand.

Alex,
I have seen something like this, but only after drug-induced eye dilation. Right, for an eye exam. Everything looked lousy 12 ways, but one of them was, on this bright winter day, edges of snow were lined with violet haze. I suppose you might have some intermittent eye condition that is similar to what the eyedrops did to me.
Ron

ATM book 2 has a brief section on "The Observer: Optical Qualities of the Eye" in the chapter on Atmosphere, Telescope, Observer.

Clear skies, Alan

Last night's presentation at the Riverside Astronomical Society was about the science of visual perception--including anatomy, optical theory, impage processing, and all that.

In addition, at the dinner before the meeting, I talked with a professional astronomer who filled me in on some more about this whole thing.

I found out that I have a 5mm F5 optical system on my face. (Actually binocular system, so I have two 5mm F5. When I was younger, I had a 7 mm F5, but as my cornea got stiffer in old age, I could not open the aperture as much.) The optical quality is not all that spectacular. It has a lot of chromatic abberation. It would not be considered even achromatic. (Luckily I have a great image procesing system that corrects for this.) I have a zoom lens for a cornea with autofocus that depends on tiny muscles.

Now, why did I get that chromatic abberration at some times, and not at others? DOn't know yet. But I have been given some tests to run if and when I notice it again.

Alex

Alex:

My vote is for atmospheric, and my reasoning is the violet on one side and yellow on the other. Depending on the altitude of the Moon and Jupiter this is pretty classic atmospheric dispersion.

Another possibility is a very very very slight fog or haze forming or even ice crystals up high in the atmosphere. I've observed from my garden observatory a few times recently where I didn't notice the fog just barely starting to form, until I looked horizontally accross at some very distant lights. It doesn't take much to refract the light coming from a distant bright object.

Because your eye is a fast singlet it produces lots of chromatic abberation which the brain proccesses out. If you were able to see it it should be uniform around the image. I have a pretty good case of astimatism and enjoy looking at bright point sources whe getting my eyes dialated for testing. I don't recall seeing differing colors on opposite edges of an object, just an oval spikey haze that shimmers with just a little bit of color all the way around the edges.

Hello:

I've often wondered about this myself, and asked my optometrist about it a while ago (I vaguely recall that her answer was that the brain is smart enough to ignore it). The only way that your eye wouldn't have chromatic aberration is if a) the cones on your retina are in different planes so that the cones for the different colors are all in focus or b) the refractive properties of the lens in your eye is such that your eye is like a doublet lens. In the eye, most of the refraction happens at the surface of the cornea, so you (and I) basically have a single lens refractor that we're all looking through. So, you'd expect to have a lot of chromatic aberration. As mentioned above, I think the best answer is that your eye does have chromatic aberration, but that your brain can ignore it most of the time. Also, in the day time, your pupil is small enough that the chromatic aberration is minimized. There are a few occasions when I think I've noticed the chromatic aberration. For example, when I've look at blue LED lights on the front of a computer, I see them surrounded by a large halo that I have not noticed around red or green LEDs. Also, I've noticed that I have a much harder time reading blue text on a black background (even if the font is very large) whereas reading red text on a black background is quite easy. The density of red cones on the fovea is much greater than the density of blue cones, which makes sense if the image quality in your eye is best in red light.

Cheers
Mike Connelley