When bright light sources, such as car headlights or streetlamps, appear distorted against a dark background, the experience is commonly referred to as glare, halos, or starbursts. This is a highly common visual complaint, particularly when driving at night. The symptom indicates that light entering the eye is not being focused correctly onto the retina, but is instead being scattered or diffused. Understanding this visual distortion is the first step toward identifying its underlying cause and finding an effective solution.
Defining Night Vision Disturbances
The symptoms experienced when lights appear blurry at night are distinct optical phenomena related to how the eye handles light in low-light conditions. These disturbances become more noticeable in the dark because the pupil dilates (mydriasis) to allow more light into the eye. As the pupil widens, it exposes the edges of the lens and cornea, which are not as optically perfect as the center, allowing peripheral light to enter and scatter.
Halos are perceived as bright, colored, or luminous rings that encircle a light source. They are often the result of light being focused at different points on the retina simultaneously, creating a blurred periphery around the central light. Glare is a general term for uncomfortable, bright light that reduces the ability to see detail and can temporarily dazzle the viewer.
Starbursts, also called streaking or flares, manifest as fine spikes or rays radiating outward from the center of a light. This effect is caused by increased light scattering within the eye’s optical system. These visual distortions are linked to higher-order aberrations (HOAs), which are subtle refractive errors beyond standard nearsightedness or astigmatism. HOAs become significantly more pronounced when the pupil is large.
Common Causes of Nighttime Blurry Lights
The underlying reasons for these nighttime visual disturbances range from simple, correctable refractive errors to more serious eye health changes. Astigmatism is one of the most frequent causes, occurring when the cornea or lens has an irregular, football-like curvature rather than a perfect sphere. This irregularity causes incoming light to scatter or focus incorrectly, which is highly noticeable as starbursts or streaks around lights.
Nearsightedness, or myopia, also contributes to night vision blurriness, often worsening the effect of halos and glare. The eye can experience a temporary increase in nearsightedness in dim light, a condition known as night myopia, which further compounds the problem. Even minor changes in a contact lens or eyeglass prescription can suddenly make these symptoms more apparent when viewing bright lights.
Ocular surface issues, such as dry eye syndrome, can be a transient cause of blurriness and glare. When the tear film on the eye’s surface is unstable or insufficient, it creates an uneven layer that scatters light as it enters the eye, reducing visual clarity. The natural lens of the eye can also be a source of trouble, as the initial clouding associated with early cataract formation directly causes light to scatter. This often produces noticeable halos and increased glare sensitivity, long before day vision is significantly affected.
For individuals who have undergone laser vision correction like LASIK, temporary or, less commonly, persistent halos and starbursts can occur. This is due to changes in the corneal shape resulting from the procedure.
When to Consult an Eye Doctor
While mild, occasional halos or starbursts in low light may be common, certain changes require prompt consultation with an eye care professional. Schedule an examination if the symptoms have a sudden onset or are rapidly worsening over a short period. A sudden, significant increase in the size or intensity of halos and glare suggests a need for immediate evaluation.
The presence of other severe symptoms alongside the blurry lights is a major warning sign. These include eye pain, a persistent headache, nausea, or vomiting, which can be indicators of acute angle-closure glaucoma, an urgent medical condition. Any sudden loss of central vision, the appearance of a dark curtain over your field of view, or new flashing lights and a shower of floaters may point to retinal issues that need urgent attention.
Solutions and Management Options
Management depends entirely on the underlying cause identified by a comprehensive eye exam. For refractive errors like astigmatism or myopia, updating the prescription in glasses or contact lenses is the primary solution. Specific prescriptions can sometimes be optimized for low-light conditions to compensate for the visual shift that occurs in the dark.
Adding anti-reflective coatings to eyeglass lenses minimizes internal reflections that contribute to glare and halos. Specialized lenses designed for night driving can filter out specific wavelengths of light to improve contrast and reduce the dazzling effect of oncoming headlights. If dry eye is the cause, using over-the-counter lubricating eye drops stabilizes the tear film and restores a smooth optical surface.
For symptoms caused by developing cataracts, surgery is the most definitive solution. The cloudy natural lens is removed and replaced with a clear artificial intraocular lens, which dramatically reduces light scattering, glare, and halos. Simple lifestyle adjustments also help, such as keeping car windshields and eyeglass lenses meticulously clean to prevent additional light scattering.