The lines most people see radiating from headlights and streetlights are usually a normal effect of how light passes through the eye, not a problem with the lights. Nearly everyone sees some rays around a bright point at night, and how long and bright they look differs from person to person. When the rays become more noticeable than they used to be, the eye is often telling you something specific, from dry eyes to an outdated prescription to a clouding lens.
What Creates the Rays You See
Doctors call the thin lines radiating from a bright light a starburst.1OVITZ. Why Do Lights Have Streaks or Lines at Night? | OVITZ Starbursts come from the eye’s own small focusing imperfections.2PubMed Central. Forward and inverse problems for symmetric starbursts A perfect eye would focus a point of light to a point. A real eye spreads it out.3Elsevier / Journal of Cataract & Refractive Surgery. Simulating the straylight effects of cataracts The center of that spread decides how sharp things look, while the faint outer spread affects glare and contrast.4Elsevier / Journal of Cataract & Refractive Surgery. Simulating the straylight effects of cataracts5Elsevier / Journal of Cataract & Refractive Surgery. Simulating the straylight effects of cataracts
The cornea, the clear dome at the front, does most of the eye’s focusing, so small irregularities in its surface bend light unevenly. The lens inside adds its own small irregularities, and the spikes you see are the combined effect of both.
Astigmatism is a common reason for streaks that run in one direction. The front of the eye is curved more in one direction than another, so light is focused unevenly and a point stretches into a line or smear. People with uncorrected astigmatism often describe lights streaking sideways or up and down, and glasses or contacts that correct it often shorten those streaks.
Because the pattern depends on the shape of your particular eye, two people looking at the same light see different rays. Your brain also gets used to your own eye’s blur, and the same blur looks worse when its pattern is turned around.6Cataract & Refractive Surgery Today. Neural Adaptation to Aberrations A new pair of glasses or a change after surgery can therefore make familiar lights look odd until you adapt.
You can check that the rays come from your eye. Close one eye, then the other: the rays often look different in each. Tilt your head and the spike pattern rotates with you, not with the light. Squinting usually shortens the rays because it narrows the opening light passes through. A camera photo of the same light won’t show your pattern.
Why Lines Around Lights Get Worse at Night
The pupil is the black opening in the middle of the colored iris, and it widens in dim light to let in more light so you can see. In daylight it is small, so light passes through the middle of the lens and cornea, the best-focused part. At night the opening can be much larger, so light also travels through the outer parts, where the shape is less regular. That is why the same streetlight can look sharp on a bright evening and spiky once it is truly dark.
In a typical eye,7Photonics. Light Disturbance Analysis and Applications a starburst at a wide night-time pupil spans about 1 degree, roughly twice the width of the full moon.8PubMed. Reducing starbursts in highly aberrated eyes with pupil miosis Shrinking the pupil to 3 mm or less can cut the rays to a quarter of a degree or smaller.9PubMed. Reducing starbursts in highly aberrated eyes with pupil miosis Light scattering inside the eye, diffraction and an uncorrected prescription all add to night-time glare as well.10Photonics. Light Disturbance Analysis and Applications
Light color matters too. Blue light makes the pupil open wider than white, red or green light of the same brightness.11PubMed Central. Effect of the chromaticity of stimuli on night vision disturbances Some bluish-white LED headlights may therefore make rays look bigger than older yellowish lamps.
It helps to name what you see. Starbursts are spikes or lines shooting out from the light. A halo is a soft ring or glowing circle around it. Glare is a general washed-out brightness that makes nearby things hard to see. Telling an eye doctor which one you notice helps narrow the cause.
Rays around headlights and taillights can hide pedestrians, lane markings or debris.12OVITZ. Why Do Lights Have Streaks or Lines at Night? | OVITZ When a bright oncoming headlight hits your eyes, the pupil narrows quickly and the rays around it are relatively small. Once the car passes, the road is dark again and the pupil takes a short time to open back up. During that recovery your vision can feel dim, and the next set of lights may look larger and spikier than the last.
Clean windscreens and glasses reduce extra scattered light that adds to streaks. If glare makes night driving feel unsafe, that’s a reason to book an eye exam.
Dry Eyes and Lights That Streak When You Blink
The thin layer of tears over the eye is the first surface light passes through. When tears break up unevenly, the eye’s surface becomes rough and scatters incoming light.13Heartland Eye Consultants. Why Are Dry Eyes Sensitive to Light & How Can It Be Treated? Dry eye can then cause glare and vision that changes with every blink.14PubMed. Mechanisms of Visual Disturbance in Dry Eye It can also make you more sensitive to light because of irritated nerves near the cornea.15Heartland Eye Consultants. Why Are Dry Eyes Sensitive to Light & How Can It Be Treated?
Some signs point to dryness. Rays sharpen for a moment right after you blink, then smear again. They are worse after screen time, reading, air conditioning or long drives, and they come with gritty, burning or tired-feeling eyes. They are often better in the morning and worse by evening.
You can test this yourself. Look at a distant light at night, such as a streetlight, without blinking for a few seconds, and notice the rays. Then blink firmly once or twice. If the rays briefly sharpen or change shape, the tear layer is likely contributing. Rays caused by the shape of the eye or by a cataract usually stay about the same whatever your eyelids do. This is a clue, not a diagnosis, because dryness can sit alongside other causes.
Dry eye does not always feel like dryness; some people notice mainly blurry or glary vision. Watery eyes can still go with dry eye, because irritation can trigger reflex tearing that doesn’t have the right makeup to coat the surface well. Streaking lights can be a dry-eye sign even when your eyes feel comfortable.
A few steps help. Blink fully and deliberately, especially during screen use and driving. Preservative-free lubricating drops before night driving can steady the tear layer. Point car vents away from your face. If drops don’t help within a few weeks, an eye doctor can check for treatable dry eye.
Cataracts and Aging Lenses
A cataract is a gradual clouding of the eye’s natural lens, common after about 60. As proteins in the lens clump and cloud, they scatter light in many directions rather than focusing it. The scattered light, which affects the faint outer spread that controls glare and contrast,16Elsevier / Journal of Cataract & Refractive Surgery. Simulating the straylight effects of cataracts spreads a glow or haze around bright sources and can lengthen the rays. The effect is strongest with a bright light against a dark background, so night is when you notice it first.
Everyday sharpness can seem fine at first. Reading-chart sharpness mostly depends on the focused central image, which an early cataract may not disturb much, while glare and contrast suffer sooner. You can read small print well and still be bothered by oncoming headlights, which is why people are sometimes told their vision is fine on a chart even though night driving has become difficult.
Over time, night driving bothers you before daytime vision does. Colors may look duller or more yellow, you may need brighter light to read, and prescription changes become frequent. When a cataract starts limiting daily life, surgery to replace the lens usually clears the haze.
Lines Around Lights After LASIK or Lens Surgery
After LASIK, starbursts at a night-time pupil can span about 1.5 degrees, half again larger than in a typical eye.17PubMed. Reducing starbursts in highly aberrated eyes with pupil miosis Pupil size and the size and placement of the treated area are the main factors after LASIK and PRK.18PubMed. Night vision disturbances after corneal refractive surgery Laser surgery reshapes the central cornea over a treated zone of a particular size. If your pupil in the dark is larger than that zone, light passes through the untreated edge as well as the treated centre. The transition between the two creates uneven focusing, which can show as starbursts and halos. Night vision complaints were more likely for people who started with high nearsightedness, had a treated zone of 6 mm or smaller, or were left slightly off target.19PubMed. Risk factors for night vision complaints after LASIK for myopia20PubMed. Risk factors for night vision complaints after LASIK for myopia21PubMed. Risk factors for night vision complaints after LASIK for myopia
Lens implants after cataract surgery can do something similar. Multifocal lens implants, which let you see near and far without glasses, cause more halos and glare than single-focus implants.22PubMed Central. Dysphotopsias or Unwanted Visual Phenomena after Cataract Surgery A multifocal implant splits incoming light so it focuses at more than one distance at once, and light focused for the other distance shows up as an out-of-focus ring or glow around bright lights. These effects are most obvious at night. Many people adapt, but some find them bothersome enough to want them addressed.
Before surgery, ask whether your pupils are large in dim light and how that affects your risk. Ask how strong your prescription is and what treatment zone size is planned. If night driving matters to you, ask about single-focus versus multifocal implants. Night effects often ease over months as the eye heals and the brain adapts.
If rays persist, a touch-up correction can fix leftover prescription error that adds streaks, and glasses for night driving can sharpen focus. Eye drops that shrink the pupil are sometimes prescribed to reduce rays. Report symptoms to your surgeon rather than waiting them out indefinitely.
When Lines and Lights Signal Something Else
Wavy or zigzag lines, and shimmering or flickering patterns that spread across your vision, are typical of migraine aura.23South Bay Retina. Retinal Flashes vs Migraine Aura: How to Tell the Difference and Protect Your Vision Aura comes from temporary changes in the brain’s vision area, not from the eye.24South Bay Retina. Retinal Flashes vs Migraine Aura: How to Tell the Difference and Protect Your Vision It usually affects both eyes, lasts 15 to 30 minutes, and clears completely.25South Bay Retina. Retinal Flashes vs Migraine Aura: How to Tell the Difference and Protect Your Vision
A common form begins as a small blind or shimmering spot near the centre of vision that slowly expands. Its edge often looks like a jagged, zigzag arc, sometimes with colors, and it tends to move outward to the side. It happens whether your eyes are open or shut, a hint that the source is not a light. Aura does not always come with a headache, so the visual episode can occur alone.
Sudden flashes of light and new floaters are most often caused by age-related changes in the gel inside the eye.26Elsevier / PubMed Central. Ageing of the vitreous: From acute onset floaters and flashes to retinal detachment The same changes can lead to retinal detachment.27Elsevier / PubMed Central. Ageing of the vitreous: From acute onset floaters and flashes to retinal detachment A sudden shower of floaters, flashes or a curtain over your vision needs same-day eye care. Retinal flashes often show at the side of vision, like a camera flash, and tend to be brief, lasting a second or less, and may repeat.
Starbursts appear only around an actual bright light and stay with it. Aura lines appear even in a dark room and drift across vision. Covering one eye can help: aura usually persists in the uncovered eye, while a problem in one eye changes or disappears when that eye is covered.
What You Can Do About Lines Around Lights
An uncorrected or outdated prescription is one of the main contributors to night-time light disturbances,28Photonics. Light Disturbance Analysis and Applications so a current eye exam with an up-to-date prescription is the first step. Because a smaller pupil shrinks rays, bright surroundings and pupil-narrowing drops can help some people.29PubMed. Reducing starbursts in highly aberrated eyes with pupil miosis
Day to day, clean glasses and windscreens inside and out, since smears add rays. Anti-reflective coatings reduce reflections on lenses. Avoid tinted “night driving” glasses, which cut light and widen pupils. Keep dashboard lights dim but not off, and avoid staring at oncoming headlights.
Book an eye exam if the rays are new or have grown noticeably in months, if night driving feels unsafe, if glare comes with blurred, hazy or faded-color vision, or if streaks are in only one eye. Any sudden flashes, floaters or vision loss need urgent care.
At the exam, the doctor checks how well you see with your current glasses, then refines your prescription with different lenses. They examine the front of the eye for dryness or corneal irregularity, and the lens for early cataract. Widening your pupils lets them look at the lens and retina closely, though it leaves you light-sensitive for a few hours and makes driving home unwise.
A short record helps. Note when the lines happen: only at night, only in one eye, or after screen time. Say whether they are spikes, rings or general haze, and whether they have changed over months. Mention any past eye surgery, new medicines, or headaches with visual symptoms.