Squinting at light bulbs, what are those lines?

[Nienstien]

Well basically, the title sums my question. When you look at a light bulb (generally works on incandescent bulbs) you can see rays coming from a few directions out from the light, it generally doesn't work on fluorescent light to my knowledge and i would like to know what causes you to see the light like so. I have thought about it and maybe it is some sort of interference pattern like double slit experiment?

 

[fawk3s]

Its cool that you bring it up. Its always seemed so natural to me and I've never questioned it since I was 3 feet high. But now that you bring it up, I do have a few theories. I am not sure if they are correct, so if I were you I'd wait for someone to confirm or bust my theory.

Have you ever looked at a lake? Seen the nice yellow sparkle of light on the water? I think these yellow rays you see when squinting have several similarities to the sparkle you see on the lake.
Look in a mirror for a second and see what happens to your eye lids when squinting - they near/approach each other. You can also see that the edges of your eye lids seem a tad more wet than the eye itself on the surface. I would suggest that this squinting pushes the water on the edges of the eye lids partially on your pupils and the rays you see are actually the sparkle of the water. The sparkle on the water is caused by polarization.

Its a theory though, and I have doubts about it.

I don't have quality sunglasses handy right now, only some cheap ones which probably don't have polarized filter, but still it was interesting to look at the lightbulb through them. The lenses are quite dark so the overall color of the rays became darker, but you could still see them fine.

 

[Xerxes1986]

I don't know exactly what you are talking about...but i suspect you are seeing images of the filaments. Squinting changes both the shape and aperature of your eye, causing an image to form..

It also could just be seeing the actual filament by reducing the intensity of the light that you see so you can distinguish the filament from the surroundings.

 

[Cleonis]

(generally works on incandescent bulbs) [...]
it generally doesn't work on fluorescent light to my knowledge

I think a key factor is whether the light source is a point source (or a good approximation to a point source).

I took an LED light, I went into the hallway of my house, switched off all lights (putting myself completely in the dark), and I looked at the white LED from a distance of 6 meters or so.

This time I observed. (Just as fawk3s I have seen it oodles of times, of course, but I never looked with an observing mindset.)With my eyes normally open I see a symmetrical effect. All around the point source my eyes experience a field of light, with a hint of rays streaming outwards, there seem to be radial lines.

Now, I know that field of light isn't there, not at the point source at least, so it must be an optical effect arising in my eyes.

Background to my hypothesis:
The surface of the cornea is not a perfect surface, the surfaces of the lens in my eye are not perfect.
Hypothesis:
In the case of the eye a percentage of the light entering it is scattered. Some of the scattered light is distributed evenly over the entire field of view, so that is not noticable. I hypothesize that some of the imperfect refraction is not distributed evenly over the entire field of view, giving rise to the appearance of a field of light surrounding the point source.

Implication of this hypothesis:
This scattering must be happening always, not just when looking at a point source in an otherwise dark environment. In daylight the scattered portion is swamped by correctly refracted light, and our visual system (including the retina itself) processes the information, making the most of it.
In an otherwise dark environment there is no other light to swamp the incorrectly refracted light.When I squint I observe yet another optical effect. I see strong, long, vertical lines of light. When I tilt my head sideways the rays go along with that. So that must be an effect that is happeing perpendicular to my eyelids. fawk3s offered the hypothesis that closing the eyelids to a very small slit gives prominence to optical effects from the fluid on the eyeball. That sounds good to me. An effect from the particular distribution of the fluid on the eyeball that you get when the eyelids are all but closed.

 

[turbo]

When I squint I observe yet another optical effect. I see strong, long, vertical lines of light. When I tilt my head sideways the rays go along with that. So that must be an effect that is happeing perpendicular to my eyelids. fawk3s offered the hypothesis that closing the eyelids to a very small slit gives prominence to optical effects from the fluid on the eyeball. That sounds good to me. An effect from the particular distribution of the fluid on the eyeball that you get when the eyelids are all but closed.

This is a typical symptom of astigmatism. Some people have rather normal visual acuity, but need glasses to correct astigmatism. Spikes of glare from oncoming headlights can make night-driving a headache for people with uncorrected astigmatism.

 

[fawk3s]

This is a typical symptom of astigmatism. Some people have rather normal visual acuity, but need glasses to correct astigmatism. Spikes of glare from oncoming headlights can make night-driving a headache for people with uncorrected astigmatism.

This seems rather reasonable.
Now I am not trying to protect my far fetched hypothesis or anything, but I think I speak for everyone when I say we have all cried as children. I remember how the effect was strongly amplified during/after crying though.