Those streaky beams radiating from headlights and street lamps are called starbursts, and they form because of imperfections in the optical system of your eye. Every eye has small irregularities in the cornea and lens that scatter incoming light, but you rarely notice them during the day because your pupil is tiny enough to block the most distorted light rays at the edges. At night your pupil opens wide, and those peripheral rays flood in, creating the spiky, radiating lines around any bright point source. The effect is universal to some degree, but certain conditions can make it dramatically worse.
How Your Eye Produces Starbursts
When you look at a distant headlight, the light enters your eye as a bundle of rays that should all converge on a single point on your retina. In practice, the cornea and lens bend the rays at the center and edges of your pupil by slightly different amounts. This mismatch, known as spherical aberration, means the peripheral rays focus at a different depth than the central ones, smearing the point of light into a halo or starburst pattern. Research using adaptive-optics systems to precisely control the amount of spherical aberration in the eye confirms that even modest changes shift where point-source lights appear sharpest and enlarge the perceived starburst pattern around bright points.1Journal of Optometry. The effect of spherical aberration on visual performance and refractive state for stimuli and tasks typical of night viewing
Pupil size is the single biggest variable. In daylight your pupil narrows to about two to three millimeters, which blocks the most aberrated outer rays and keeps the image clean. In darkness your pupil can dilate to six or seven millimeters, tripling the area through which light enters and dramatically increasing the contribution of those edge-of-lens imperfections. A study modeling starburst geometry in eyes with significant aberrations found that at a 7 mm pupil the starburst diameter reached roughly 1.5 degrees, but shrank to a quarter of a degree or less when the pupil was constricted to 3 mm or smaller.2PubMed. Reducing starbursts in highly aberrated eyes with pupil miosis That is why starbursts are almost exclusively a nighttime complaint: the same eye that sees clean point sources during the day lets in enough stray light after dark to turn every oncoming headlight into a spiky mess.
Why It Gets Worse With Age
If you feel like nighttime driving has gotten harder over the years, you are not imagining it. The crystalline lens inside your eye gradually loses its transparency with age. Even before a full cataract develops, subtle protein clumping and yellowing scatter more light, increasing the glow around headlights. Measurements of how much glare reduces your ability to see contrast paint a stark picture: for a healthy person in their late seventies, oncoming low beams cut contrast roughly 50% more than they do for a young adult, and when early cataract is present the contrast loss can nearly triple compared to a young eye.3PubMed Central. Disability Glare in the Aging Eye. Assessment and Impact on Driving
Recovery time compounds the problem. After an oncoming car passes, your retina needs to readapt to the darker road ahead. Older adults require about three times as long to recover sensitivity to low-contrast objects compared to younger drivers.4Proceedings of the Human Factors and Ergonomics Society Annual Meeting. Age and Glare Recovery Time for Low-Contrast Stimuli So an older driver not only sees a larger, brighter starburst when a headlight appears, but also spends more seconds partially blinded after it passes. That combination matters for spotting pedestrians, potholes, and lane markings.
In a simulated night-driving study of older adults, the introduction of a glare source lowered contrast sensitivity by an average of about 41%, and overall contrast sensitivity declined at a rate that worked out to a meaningful drop every decade of life.5Frontiers in Human Neuroscience. Contrast Sensitivity and Night Driving in Older People: Quantifying the Relationship Between Visual Acuity, Contrast Sensitivity, and Hazard Detection Distance in a Night-Time Driving Simulator Standard letter-chart eye exams, which are done in bright, evenly lit rooms, routinely miss this kind of deficit. You can read the 20/20 line in the clinic and still struggle to see lane edges through oncoming headlight glare.
Eye Surgery and Artificial Lenses
Laser vision correction and lens implant surgery can introduce or worsen starbursts and halos, sometimes dramatically. After LASIK, the reshaped cornea often has a sharper transition between the treated central zone and the untouched periphery. When the pupil dilates beyond that treated zone at night, the mismatch in curvature scatters light outward in distinctive rays. Post-LASIK eyes with larger amounts of higher-order aberration show starburst patterns around 1.5 degrees across at a 7 mm pupil, compared to about 1 degree for a normal presbyopic eye.2PubMed. Reducing starbursts in highly aberrated eyes with pupil miosis
Intraocular lenses implanted during cataract surgery create their own version of the phenomenon. Multifocal lens designs intentionally split light into multiple focal points so you can see both near and far. The trade-off is that the out-of-focus portion of the light forms rings and halos around point sources. In one clinical study, 23 out of 24 patients with a refractive multifocal lens reported halos when looking at bright lights at night, and under controlled testing conditions halos were measurable in every single patient.6PubMed. Halo size under distance and near conditions in refractive multifocal intraocular lenses The brain adapts over months and many people eventually tune out the rings, but for a subset the glare remains a persistent complaint.
Pupil size is again a key player. In patients with newer multifocal diffractive lenses, larger pupil sizes correlated with both brighter and physically larger halos and starbursts.7Scientific Reports. Risk factors for photic phenomena in two different multifractive diffractive intraocular lenses That is one reason surgeons evaluate your natural pupil diameter before recommending a specific lens design. If you have naturally large pupils, the conversation about whether to accept a multifocal lens versus a standard one should be especially thorough.
One emerging area of research involves blue-light-filtering lenses, which tint the implant slightly yellow. A study comparing these to clear implants found that halo size was roughly half as large with the blue-light-filtering design, and starburst size was also significantly smaller.8Current Eye Research. The Effects of Blue-Light Filtering Intraocular Implants on Glare Geometry The mechanism is thought to be simple wavelength filtering: shorter blue wavelengths scatter more easily inside the eye, so blocking some of them before they hit the retina reduces the size of the light spread.
Dirty Lenses, Contact Lenses, and Other Everyday Culprits
Before you assume something is wrong with your eyes, check what is sitting in front of them. Smudged, scratched, or dusty eyeglasses scatter light across your visual field and enlarge the glow around every light source. A study comparing halo sizes found that people wearing unclean spectacles saw significantly larger halos than people with normal vision or clean glasses, and the difference disappeared once the lenses were properly cleaned.9Clinical and Experimental Optometry. Glare and halo with refractive correction A fingerprint smear on the lens that is invisible during the day turns into a scattering surface under a headlight beam.
Contact lenses produced larger halos than clean spectacles in the same study, even when the contacts themselves were clean.9Clinical and Experimental Optometry. Glare and halo with refractive correction The tear film on a contact lens creates an additional refracting surface that fluctuates with each blink. Deposit buildup, dryness, or a lens that has shifted slightly off center can all add scatter. If you wear contacts and notice worsening starbursts, try switching to fresh daily disposables or wearing your glasses on a nighttime drive to see whether the effect changes.
Your windshield matters too. A hazy interior film from off-gassing plastics, or a scratched exterior surface, acts the same way a dirty spectacle lens does, spreading light across your field of view. A thorough interior and exterior clean with a glass-specific cleaner can make a noticeable difference.
Medications That Dilate Your Pupils
Because pupil size drives so much of the starburst effect, any drug that enlarges your pupils can intensify what you see at night. Anticholinergic medications are the most common class to watch for. These include certain antihistamines, overactive-bladder drugs, older antidepressants, and some anti-nausea medications. Adrenergic agents, including some decongestants, can also widen the pupil.10Drug Safety. Drug-induced ocular disorders The pupil dilation from a single dose of an over-the-counter allergy pill may be subtle, but it can push your pupil a millimeter or so wider than usual, and that extra millimeter lets in enough additional aberrated light to turn modest starbursts into distracting ones.
If you have started a new medication and noticed that nighttime driving has become more glare-prone, mention it to your prescriber. In many cases an alternative drug with fewer anticholinergic effects exists and can make a real practical difference after dark.
Are Modern LED Headlights Making Things Worse?
A common complaint is that newer vehicles with bright white or bluish LED headlights are more blinding than the warmer halogen bulbs they replaced. The intuition is reasonable: LEDs emit more short-wavelength blue light, and blue light scatters more readily through the eye’s optical media. But the research on this is more nuanced than the gut feeling suggests. A study directly measuring both disability glare and discomfort glare from LED lamps at different color temperatures found that the cooler, bluer 6500 K lamp did not produce significantly more visual impairment than a warmer lamp, likely because the eye’s macular pigment absorbs much of the short-wavelength light before it reaches the photoreceptors.11Human Factors. Glare at Night-Time Driving: Effect of Correlated Color Temperature of Led Lamps
That does not mean LED headlights are harmless. The total luminous intensity of many modern headlight systems is simply higher than older designs, and misaimed or aftermarket LED bulbs in reflector housings not designed for them can throw light far above the intended cutoff line. The color temperature itself is a poor predictor of glare severity, but the raw brightness of a badly aimed headlight is a very good one. If oncoming LEDs bother you more than halogens did, the problem is more likely intensity and aim than wavelength.
What Actually Helps
Given how many factors pile on, there is no single fix, but several interventions make a measurable difference.
Anti-reflection coatings on prescription glasses are one of the more straightforward upgrades. Uncoated lenses reflect roughly 8% of incoming light off their surfaces, some of which bounces around inside the lens and reaches your eye as scattered glow. An AR coating brings transmittance up to about 99%, and in a crossover study of highway patrol officers who depend on night vision for their jobs, the AR-coated lenses were rated significantly better for glare reduction and nighttime clarity.12Journal of the American Optometric Association. Comparison between anti-reflection-coated and uncoated spectacle lenses for presbyopic highway patrol troopers
Yellow-tinted “night driving” glasses are heavily marketed, but the evidence for them is weak. By filtering out blue light and reducing overall light transmission, they do lower the subjective feeling of discomfort from oncoming headlights.13JAMA Ophthalmology. Comparison of Pedestrian Detection With and Without Yellow-Lens Glasses During Simulated Night Driving With and Without Headlight Glare But reducing the total amount of light reaching your retina at night comes with an obvious cost: everything else gets dimmer too. The road, pedestrians, and obstacles all lose contrast. If your primary concern is seeing starbursts around lights, yellow lenses may mask them slightly while simultaneously making it harder to see the things that actually matter for safety.
A few other practical steps help without trade-offs:
- Clean your glasses and windshield: As noted earlier, surface deposits scatter light and enlarge halos. A microfiber cloth and proper glass cleaner cost almost nothing and can reduce perceived glare substantially.
- Keep your prescription current: An outdated glasses or contact lens prescription can leave you slightly under- or over-corrected, and both states increase optical aberrations at night.
- Use your dashboard dimmer: Bright interior lighting constricts your pupils less than you’d expect and washes out your dark adaptation. Dim the instrument cluster and any screens to the lowest comfortable level.
- Look slightly to the right: When an oncoming vehicle’s headlights are directly in your line of sight, shifting your gaze toward the right lane edge keeps the brightest light off your fovea and speeds recovery once the car passes.
When Starbursts Signal Something That Needs Treatment
Some degree of starburst and halo vision is normal for every human eye in the dark. The question is whether yours has changed, or whether it interferes with safe driving. A few scenarios warrant an eye exam sooner rather than later.
A sudden increase in halos or starbursts, especially with eye pain or redness, can signal an acute rise in eye pressure. Angle-closure glaucoma produces classic rainbow-colored halos around lights and is a medical emergency. Certain medications, including the anticholinergic and adrenergic drugs mentioned earlier, can trigger this in susceptible individuals.10Drug Safety. Drug-induced ocular disorders
A gradual worsening over months to years, particularly if paired with fading color perception or increasing difficulty with road signs, often points to cataract progression. Cataracts scatter light broadly and are the most common treatable cause of nighttime glare complaints in people over 60. Modern cataract surgery replaces the cloudy lens with a clear artificial one and typically reduces glare, though as discussed, the choice of implant lens type influences whether halos persist afterward.
If you have had LASIK, PRK, or another corneal refractive procedure and your night vision symptoms have worsened or never resolved, a corneal topography map can reveal residual irregularities. Wavefront-guided retreatments exist specifically to smooth these out, though candidacy depends on corneal thickness and the specific pattern of aberration.14American Journal of Ophthalmology. Corneal Wavefront-Guided Retreatments for Significant Night Vision Symptoms after Myopic Laser Refractive Surgery
Dry eye is an easily overlooked contributor. A disrupted tear film creates an irregular optical surface over the cornea, adding scatter. Many people are driest at the end of the day, which is exactly when they are driving home in the dark. Preservative-free artificial tears used before a nighttime drive can temporarily smooth the tear film and reduce starburst symptoms without any lasting commitment to treatment.
Keratoconus and Other Corneal Irregularities
Keratoconus is a condition in which the cornea gradually thins and bulges into a cone shape, introducing high levels of irregular astigmatism and higher-order aberrations. People with keratoconus often report severe starbursts and ghosting around lights that go well beyond what a normally shaped cornea produces. The starburst modeling study cited earlier grouped keratoconic eyes alongside post-LASIK eyes as examples of “highly aberrated” optical systems, both producing starbursts substantially larger than those of a normal eye at the same pupil diameter.2PubMed. Reducing starbursts in highly aberrated eyes with pupil miosis
Keratoconus typically starts in the teens or twenties and progresses at different rates. If you are young and your night-driving starbursts are getting worse year over year, especially if your glasses prescription seems to shift frequently, a corneal topography scan can detect the characteristic thinning pattern. Early-stage treatment with corneal cross-linking can stiffen the cornea and slow progression. Rigid gas-permeable contact lenses or scleral lenses are the standard optical correction, because they create a smooth, regular refracting surface over the irregular cornea, which reduces scatter far more effectively than soft contacts or glasses.
Other corneal conditions, including corneal dystrophies and scarring from prior infection or injury, can produce similar scattering effects. Any corneal irregularity that disrupts the smooth, even curvature of the front surface of the eye will let stray light through in unpredictable directions, creating the characteristic rays, halos, or ghosted images that make nighttime point-source lights so distracting.