# Why do we see streaks of light? **URL:** \ **Category:** Factual Questions\ **Created:** [July 23, 2012, 2:04am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099 "2012-07-23T02:04:56Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![IceQube](https://avatars.discourse-cdn.com/v4/letter/i/dfb087/32.png) [@IceQube](https://boards.straightdope.com/u/IceQube)\ **Post date:** [July 23, 2012, 2:04am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/1 "2012-07-23T02:04:56Z")
Why do we see long streaks of light when driving? Is it because of the windshield? And why do we even see streaks of light when we are not driving? Is it because of our eyelashes? Edit: These streaks extend from light sources such as a light bulb or a car headlight. ---
**Author:** ![bobot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bobot/32/21622_2.png) [@bobot](https://boards.straightdope.com/u/bobot)\ **Post date:** [July 23, 2012, 2:34am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/2 "2012-07-23T02:34:06Z")
I don’t really understand your question. ---
**Author:** ![jackdavinci](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackdavinci/32/3259_2.png) [@jackdavinci](https://boards.straightdope.com/u/jackdavinci)\ **Post date:** [July 23, 2012, 2:41am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/3 "2012-07-23T02:41:14Z")
Look up “lens flare”. ---
**Author:** ![IceQube](https://avatars.discourse-cdn.com/v4/letter/i/dfb087/32.png) [@IceQube](https://boards.straightdope.com/u/IceQube)\ **Post date:** [July 23, 2012, 3:45am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/4 "2012-07-23T03:45:11Z")
> [@jackdavinci](#): > > Look up “lens flare”. The effect is similar, but the effect I’m describing pertains to biological systems. You can probably visualize the same effect by looking at a ceiling light. A bright one at that. Or even better, try looking at a street light at night. You will see streaks of light extending from the street light. ---
**Author:** ![tellyworth](https://avatars.discourse-cdn.com/v4/letter/t/977dab/32.png) [@tellyworth](https://boards.straightdope.com/u/tellyworth)\ **Post date:** [July 23, 2012, 4:05am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/5 "2012-07-23T04:05:30Z")
Do you mean [diffraction spikes](http://en.wikipedia.org/wiki/Diffraction_spike), or something else? ---
**Author:** ![IceQube](https://avatars.discourse-cdn.com/v4/letter/i/dfb087/32.png) [@IceQube](https://boards.straightdope.com/u/IceQube)\ **Post date:** [July 23, 2012, 4:21am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/6 "2012-07-23T04:21:14Z")
> [@tellyworth](#): > > Do you mean [diffraction spikes](http://en.wikipedia.org/wiki/Diffraction_spike), or something else? The effect is similar, but are the causes similar? ---
**Author:** ![tellyworth](https://avatars.discourse-cdn.com/v4/letter/t/977dab/32.png) [@tellyworth](https://boards.straightdope.com/u/tellyworth)\ **Post date:** [July 23, 2012, 4:36am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/7 "2012-07-23T04:36:18Z")
Probably. How many spikes do you see? Which way are they oriented? In photography, they happen when you have a strong point-source light and a narrow aperture. The shape and orientation is defined by the aperture blades (unless you use a special filter over the lens, in which case they’re caused by a fine grating). ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [July 23, 2012, 4:45am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/8 "2012-07-23T04:45:00Z")
Are you referring to rays that emanate outward from a light source? When I had a cataract in one eye, these rays became so distracting that I had to drive at night with that eye closed. Cataract surgery fixed that. ---
**Author:** ![IceQube](https://avatars.discourse-cdn.com/v4/letter/i/dfb087/32.png) [@IceQube](https://boards.straightdope.com/u/IceQube)\ **Post date:** [July 23, 2012, 6:06am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/9 "2012-07-23T06:06:04Z")
> [@panache45](#): > > Are you referring to rays that emanate outward from a light source? > > When I had a cataract in one eye, these rays became so distracting that I had to drive at night with that eye closed. Cataract surgery fixed that. Yes, rays emanate outward from a light source (at least for me). I don’t, however, have cataracts. It isn’t distracting enough to take away from driving safely either. It’s just an interesting phenomenon. What is it called, and am I one of a few who observe this phenomenon? ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [July 23, 2012, 7:13am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/10 "2012-07-23T07:13:33Z")
The effects you describe are related to both lens flare and diffraction spikes. Light entering the eye scatters off the surface of the cornea (if it is damaged), the protein crystals that form the lens of the eye (and is worse as it clouds due to cataracts) and floaters (dead cells) in the aqueous humour of the eye. All the scattered light can interfere in ways that cause halos, ghosts and spikes in the vision. As **panache45** noted, cataracts can exacerbate the problem, as can laser eye vision correcting surgery (or any injury that damages the surface of the eye). It is not unique - it it pretty common for people to see them. All that medieval art with halos and spikes round saints heads illustrates the fact that people have been seeing these effects for centuries. If you have concerns, or are worried that they are interfering with your night driving vision (as per **panache45** ), talk to an ophthalmologist. Si ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [July 24, 2012, 11:54am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/11 "2012-07-24T11:54:31Z")
I find I see them more when I’m tired, and/or if my eyes are “bleary” or watering. I assume the layer of fluid on the eyeball diffracts the light more. Edit: I just experimented with the LED on my monitor (the only point source of light to hand). If I screw my eyes up a bit I can get long “spikes” of light at the 12 and 6 o’clock positions. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [July 24, 2012, 4:34pm UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/12 "2012-07-24T16:34:55Z")
Another possibility is your windshield wipers are smearing road salt and dirt on your windshield, rather than wiping them clean. Do you mostly see the rays when looking through the windshield, or at least, are the ones you see through the windshield different from the ones you see through your eyelashes? Are the lines perpendicular to the direction the wipers wipe? ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [July 24, 2012, 4:45pm UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/13 "2012-07-24T16:45:07Z")
> [@IceQube](#): > > > [@jackdavinci](#): > > > > Look up “lens flare”. > > The effect is similar, but the effect I’m describing pertains to biological systems. So what? The eye still has a lens, and other relevant optical components. Lens flare can occur regardless of whether the lens, etc is made of glass or of squishy stuff. However, I think diffraction effects, and eyelashes, can probably also sometimes play a role in this effect, in addition to the sorts of internal reflections that cause lens flare in cameras. ---
**Author:** ![tellyworth](https://avatars.discourse-cdn.com/v4/letter/t/977dab/32.png) [@tellyworth](https://boards.straightdope.com/u/tellyworth)\ **Post date:** [July 24, 2012, 11:50pm UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/14 "2012-07-24T23:50:57Z")
There’s a simple experiment you can do to determine whether it’s caused by you or by something around you: tilt your head. If the streaks tilt with you, it’s your eyes or eyelashes. If they don’t, it’s your car. ---
**Author:** ![drewtwo99](https://avatars.discourse-cdn.com/v4/letter/d/d07c76/32.png) [@drewtwo99](https://boards.straightdope.com/u/drewtwo99)\ **Post date:** [July 25, 2012, 1:12am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/15 "2012-07-25T01:12:12Z")
The effect you are describing is known as a starburst. [Here is an example of a photo demonstrating starbursts.](http://www.georgeandreou.net/storage/IMG_7682a.JPG) ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [July 25, 2012, 1:49pm UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/16 "2012-07-25T13:49:31Z")
> [@drewtwo99](#): > > The effect you are describing is known as a starburst. > > [Here is an example of a photo demonstrating starbursts.](http://www.georgeandreou.net/storage/IMG_7682a.JPG) But with cataracts, _ **all** _ the lights had this effect. Christmas time was hell. ---
**Author:** ![misling](https://avatars.discourse-cdn.com/v4/letter/m/3ab097/32.png) [@misling](https://boards.straightdope.com/u/misling)\ **Post date:** [July 25, 2012, 7:44pm UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/17 "2012-07-25T19:44:11Z")
I’m extremely nearsighted and also have a fairly large astigmatism in one eye. I get those rays from point light sources when I don’t wear my glasses. If I move my head, or my eyes, the rays twist about. - as a kid I thougt everybody saw that way. I always wondered if the astigmatism caused it (lens isn’t round, it has a torque). The ‘Starry Night’ van Gogh painting illustrates the effect pretty well, except I’m too nearsighted to see it on stars. I mostly saw it on things like streetlights. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [July 25, 2012, 8:13pm UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/18 "2012-07-25T20:13:07Z")
> [@panache45](#): > > Are you referring to rays that emanate outward from a light source? > > When I had a cataract in one eye, these rays became so distracting that I had to drive at night with that eye closed. Cataract surgery fixed that. This is what I’m wondering. I don’t see “long streaks of light” in headlights or anything. I might see a starburst pattern, or a diffraction caused by glass, but directly looking at the light without a glass medium in between, I don’t see long streaks at all. ---
**Author:** ![zseml](https://avatars.discourse-cdn.com/v4/letter/z/a88e57/32.png) [@zseml](https://boards.straightdope.com/u/zseml)\ **Post date:** [April 27, 2013, 5:55am UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/19 "2013-04-27T05:55:45Z")
has anyone gotten a really definitive answer on this? i have a very similar problem where if i look back and forth, i see the “starburst” or “lens flare” effect that kind of rotates as my eyes settle on a position and focus. it’s really irritating and I’ve seen an optometrist and an ophthalmologist who have said it’s nothing to worry about. that said, it’s still very annoying and they didn’t give me a very good explanation of what causes it. anyone have a good explanation? 🙂 looking for something to help put my mind at ease. ---
**Author:** ![stiz](https://avatars.discourse-cdn.com/v4/letter/s/e56c9b/32.png) [@stiz](https://boards.straightdope.com/u/stiz)\ **Post date:** [April 4, 2019, 8:04pm UTC](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099/20 "2019-04-04T20:04:03Z")
Someone mentioned diffraction streaks… that’s the right answer. Diffraction is light spreading out behind obstacles after running into them. Normally they are objects that are small by human standards because the phenomenon is created when the size of the obstacle is similar to the wavelength of the wave… in this case it would be eyelashes or the corners of your eyes for normal eyes. [Next page](https://boards.straightdope.com/t/why-do-we-see-streaks-of-light/629099.md?page=2)