Halos Around Lights
What Causes Halos Around Lights
Halos form when light scatters or bends unevenly as it passes through your eye. According to the AAO, any opacity or irregularity in the cornea, lens, or vitreous can cause light to spread into rings or glows around light sources instead of focusing sharply on your retina.
You notice halos most in low light or at night because your pupils dilate wider, allowing more scattered light to reach your retina. Driving after dark or looking at streetlights makes halos more obvious.
Cataracts are one of the most common causes of halos. According to the NEI, trouble seeing or driving at night is one of the first symptoms people notice as a cataract develops. The clouded lens scatters incoming light, creating glare and halo effects around headlights, streetlights, and lamps.
As the cataract grows, halos and glare worsen. Cataract surgery replaces the clouded lens with a clear artificial one, which eliminates this source of light scattering.
Halos with sudden severe eye pain, nausea, vomiting, and redness can signal acute angle-closure glaucoma. According to the AAO, the sudden rise in eye pressure causes the cornea to swell, which scatters light and produces halos. This is an emergency that requires immediate treatment to prevent permanent vision loss.
If you experience halos with intense eye pain and nausea, go to an emergency room or call your eye doctor immediately. Do not wait for the symptoms to pass on their own.
Fuchs endothelial dystrophy causes corneal swelling that produces halos, in the morning when swelling peaks. Keratoconus (irregular corneal shape) scatters light in unpredictable patterns, causing halos and ghosting. Photokeratitis (UV sunburn of the cornea) can cause temporary halos until the corneal surface heals.
Any condition that disrupts the smooth, clear surface of your cornea can cause light to scatter into halo patterns.
Halos After Eye Surgery
Halos and glare at night are common after LASIK, in the first few months. According to the AAO, this occurs because the treatment zone on the cornea has a defined edge that can scatter light when your pupil dilates wider than the zone in dim conditions.
Most post-LASIK halos fade over weeks to months as your cornea stabilizes and your brain adapts to the new optics. If halos persist or worsen after six months, your surgeon can evaluate whether an enhancement procedure would help.
Multifocal intraocular lenses (IOLs) placed during cataract surgery create multiple focus points, which can produce halos and glare as a side effect. According to the AAO, this is called positive dysphotopsia. Most patients experience gradual neuroadaptation as the brain learns to filter out the extra light patterns.
Persistent severe halos from multifocal IOLs should prompt evaluation of lens position. In rare cases, exchanging the lens for a monofocal design resolves the problem.
Corneal transplant, glaucoma surgery, and retinal procedures can all cause temporary halos while the eye heals. Swelling, inflammation, and changes in fluid dynamics within the eye contribute to light scattering during recovery.
Follow your surgeon's postoperative instructions and attend all follow-up appointments. Report new or worsening halos during your recovery period so your surgeon can check for complications.
Other Causes of Halos
According to the AAO, halos associated with pigment dispersion syndrome may appear after physical exercise. Pigment granules from the iris release into the front chamber of the eye during activity, temporarily scattering light. These halos are transient and resolve as the pigment settles.
Over time, accumulated pigment can clog the eye's drainage system and cause pigmentary glaucoma. If you notice halos during or after exercise, mention this to your eye doctor for monitoring.
An uneven or insufficient tear film scatters light across your cornea, producing mild halos and blurry vision. Blinking refreshes your tear film and may temporarily reduce the effect. Preservative-free artificial tears can improve tear film stability and reduce halo symptoms from dryness.
This cause of halos is common and benign. If drops resolve your halos, dryness is the culprit rather than a structural eye problem.
Nearsightedness, farsightedness, and astigmatism can all produce halos and glare, at night. Light entering the eye at incorrect angles due to the refractive error spreads across the retina instead of focusing to a sharp point. Updated glasses or contact lenses correct this.
If you notice halos mainly while driving at night, check whether your prescription is current. Even a small change in your refraction can produce noticeable night symptoms.
When to See Your Eye Doctor About Halos
Seek immediate care if halos appear suddenly with eye pain, redness, nausea, or vomiting. This combination suggests acute angle-closure glaucoma, which can cause permanent vision loss within hours if untreated. Go to the nearest emergency room.
Sudden halos with headache and blurred vision after a blow to the head or eye also require urgent evaluation.
Schedule an appointment if you notice halos developing gradually, if they interfere with night driving. Worsening halos over weeks or months can indicate cataract progression, corneal changes, or other conditions that benefit from early treatment.
Halos that appear only in the morning and improve during the day suggest corneal edema, which your eye doctor can evaluate with a simple measurement of corneal thickness.
Your eye doctor will examine your cornea, lens, eye pressure, and overall eye structure to identify the source of your halos. They may perform a slit-lamp exam, measure corneal thickness, check for cataracts, and test your eye pressure. The cause determines the treatment, which can range from new glasses to dry eye therapy to cataract surgery.
Bring notes about when your halos occur, how long they last, and whether other symptoms accompany them. This information helps your eye doctor narrow down the diagnosis.
Halos Around Lights: Common Questions
No. Dry eyes, mild refractive errors, and dirty glasses can all cause halos that are harmless and easy to fix. Halos become concerning when they appear suddenly with pain, worsen over time, or interfere with driving. An eye exam can distinguish harmless causes from those that need treatment.
Cataract-related halos get worse over time as the lens becomes more clouded. Cataract surgery is the only treatment that eliminates them by replacing the clouded lens with a clear artificial one. The timing of surgery depends on how much the halos and glare affect your daily life.
Most post-LASIK halos improve within three to six months as your cornea heals and your brain adapts. A small number of patients experience persistent halos beyond six months, which can be evaluated for possible enhancement. Halos are more common in patients with larger pupils or higher prescriptions.
If your halos result from dry eyes or tear film irregularity, artificial tears can reduce the effect. Drops will not help halos caused by cataracts, refractive errors, or structural problems inside the eye. Your eye doctor can determine whether drops are an appropriate treatment for your situation.
Rainbow-colored halos occur when light diffracts through moisture or irregularities on or in the eye, separating into its color components. Corneal edema, acute glaucoma, and mucus on the eye surface can all produce rainbow halos. New rainbow halos, with pain, warrant prompt evaluation.
If halos make it difficult to see road signs, lane markings, or other vehicles clearly, limit your night driving until your eye doctor evaluates the cause. Cataracts, uncorrected prescriptions, and dry eye are all treatable causes. Once addressed, your night driving vision can improve.
Get Your Halos Evaluated
If you see halos around lights, schedule a comprehensive eye exam. Your eye doctor can identify the cause and recommend the right treatment, whether that means updated glasses, dry eye therapy, or surgery. Halos that interfere with your daily activities deserve attention.