Many people experience seeing lines, starbursts, or halos around lights, a common visual phenomenon. This is often more noticeable in low-light conditions or at night, creating patterns around bright sources like headlights or streetlights. Understanding why these visual distortions appear involves exploring how light interacts with the eye’s structures.
Understanding Light and Your Eye
Light enters the eye through the cornea, the transparent outer layer that bends light. It then passes through the pupil, the opening in the iris that controls light entry. The lens further focuses light onto the retina. The retina, a light-sensitive tissue, converts light into electrical signals for the brain to interpret as an image. Imperfections or scattering of light within any of these structures, or even in the tear film covering the eye’s surface, can lead to visual distortions like lines or starbursts.
Common Explanations for Seeing Lines
Astigmatism, a common refractive error, is a frequent reason for seeing lines around lights. It occurs when the cornea or lens has an irregular shape, causing light to bend unevenly. This prevents light from focusing sharply on the retina, instead scattering it into streaks or starbursts. Even minor astigmatism can lead to these visual effects, which often become more apparent in dim lighting when the pupil dilates, allowing more unfocused light to enter the eye.
Dry eyes are another common cause of light distortions. A healthy eye has a smooth, stable tear film that lubricates the surface and ensures proper light refraction. When this tear film is insufficient or unstable, the ocular surface becomes irregular, causing light to scatter erratically. This light scattering can manifest as increased sensitivity to light, glare, or the perception of lines and halos.
Light diffraction also contributes to seeing lines. Light bends around obstacles or through small openings, occurring as it passes through the eye’s pupil, especially when the pupil is larger in low light. Tiny imperfections in the eye’s structures, such as variations on the cornea or lens, or even dust on glasses, can also cause light to diffract and create streaks. These effects are often more pronounced with very bright light sources and are a typical part of how the human eye processes light.
When Lines Signal a Deeper Issue
While often harmless, lines around lights can sometimes signal underlying eye conditions. Cataracts involve the clouding of the eye’s clear lens, often occurring with aging. As the lens clouds, it scatters light, leading to blurred vision, glare, and halos or lines around lights, especially at night. The severity of these visual disturbances can increase as the cataract progresses.
Corneal irregularities, beyond common astigmatism, can also cause distortions. Conditions like keratoconus, where the cornea thins and bulges into a cone shape, can distort vision by irregularly deflecting light. Injuries or diseases of the cornea can also lead to an uneven surface that scatters light, resulting in blurred vision, double vision, or light sensitivity. These irregularities disrupt the cornea’s ability to focus light onto the retina.
Lines or starbursts may also occur following refractive surgeries like LASIK. While LASIK reshapes the cornea, healing or subtle corneal changes can sometimes induce higher-order aberrations, microscopic irregularities that scatter light. These effects are often temporary, with many patients experiencing a reduction in glare and halos within months as the eye heals. However, in some cases, these visual changes can persist or may signal the need for further evaluation.
When to Consult an Eye Doctor
While seeing lines around lights can be normal, certain accompanying symptoms warrant professional attention. Consult an eye care professional promptly if you experience a sudden onset of new or worsening lines, starbursts, or halos. Immediate evaluation is recommended if these disturbances are accompanied by eye pain, persistent redness, a decrease in vision, or new floaters or flashes of light. These symptoms could indicate underlying conditions that require timely diagnosis and treatment to protect your vision.