The experience of seeing bright lights, especially at night, appear distorted with radiating lines is a common complaint. When the visual system functions perfectly, a pinpoint light source, like a distant headlight, focuses as a single, clear point on the retina. If light is scattered as it travels through the eye, it transforms the point of light into an elongated streak or a star-like pattern. This phenomenon has specific names that help eye care professionals identify the source of the distortion.
Defining Visual Disturbances
The visual disturbance commonly described as seeing lines in lights is technically known as a starburst. Starbursts appear as multiple fine lines or spikes that radiate outward from a central light source, resembling the points of a star. They are often most pronounced around bright lights in dark environments, such as car headlights or streetlights.
This is distinct from two other common light-related distortions. Glare is an uncomfortable, blinding brightness that washes out vision. Halos are distinct, concentric rings or circles of light that surround the source, often appearing iridescent or rainbow-colored. Recognizing the specific appearance helps pinpoint the underlying cause.
How Light Scattering Causes Streaks
The fundamental cause of these light distortions is light scattering, also known as ocular straylight. For light to form a perfect image, it must pass uninterrupted through the eye’s clear structures: the tear film, cornea, and lens. Any minute irregularity in these structures disrupts the light’s path, causing it to scatter instead of refracting cleanly to a single focal point on the retina.
The scattered light hits the retina over a wider area, creating the perception of streaks or rings. This is similar to how a smudged camera lens turns a bright light source into a blurry mess. Light scattering is often more noticeable at night because the pupil dilates, allowing light to pass through the peripheral parts of the lens and cornea, where irregularities are frequently more pronounced.
The specific pattern of the starburst often depends on the type of irregularity. For example, a non-uniform corneal surface can cause an asymmetrical starburst, while internal lens changes may create a more symmetrical, spiky pattern.
Common and Temporary Triggers
Many common, non-disease-related factors can cause temporary starbursts or glare. The most frequent culprit is an unstable tear film, commonly associated with dry eye syndrome. When the tear film is not smooth and uniform, it creates an irregular surface that scatters light as it enters the eye.
Similarly, a dirty pair of eyeglasses or contact lenses can produce a scattering effect. Smudges or deposits on the lens surface act as microscopic obstacles, deflecting light before it reaches the eye. Even without an underlying condition, the natural dilation of the pupil in low light increases light scattering. A larger pupil size allows more peripheral light rays to enter, which are harder for the eye’s optics to focus perfectly, leading to increased starbursts and glare.
Starbursts are also a known side effect following refractive surgeries, such as LASIK. This is often temporary, resulting from the healing process and the new corneal curvature, but it can persist in some cases. These effects often resolve as the eye heals or can be managed by improving tear film stability with lubricating drops.
Underlying Medical Conditions
When visual disturbances are persistent, worsening, or significantly interfere with daily life, they may signal a progressive medical condition. A primary cause of increasing starbursts and glare is the development of cataracts, which involves the clouding of the eye’s natural lens. As the lens becomes opaque, it scatters light more aggressively, causing the bright light source to spread into noticeable streaks and halos.
Conditions affecting the clear front surface of the eye, the cornea, are also implicated. Corneal diseases like keratoconus, where the cornea thins and bulges into a cone shape, or Fuchs’ Dystrophy, which causes corneal swelling, can severely distort light pathways. Any scarring or edema on the cornea creates an irregular surface that causes light to scatter.
A sudden onset of halos or glare, especially when accompanied by severe eye pain, headache, nausea, or vomiting, may indicate a medical emergency like acute angle-closure glaucoma. This condition involves a rapid increase in fluid pressure inside the eye, which causes corneal swelling and leads to the perception of rainbow-colored rings around lights. If visual disturbances are sudden, painful, or rapidly worsening, seeking immediate attention from an eye care professional is prudent.