Halos in vision describe a common visual phenomenon where bright light sources appear to have luminous rings or circles around them. These rings can sometimes be a normal response of the eye to light, but they can also indicate underlying eye conditions. While often harmless, halos can occasionally signal a more serious issue requiring professional attention.
Understanding Halos in Vision
Halos appear as bright, often rainbow-colored, circles around light sources, like streetlights or car headlights, especially noticeable in dim lighting or at night. This visual effect arises from the optical principle of diffraction. Diffraction occurs when light bends slightly as it passes around the edges of an object or through small openings. When light enters the eye, it interacts with various structures, and any irregularities can cause it to scatter or bend in a way that creates these halo effects.
The appearance of halos is fundamentally linked to how light propagates through the eye’s optical system. Instead of focusing sharply onto the retina, some light rays are dispersed, creating the perception of a luminous ring. This scattering can be influenced by the shape and clarity of the eye’s components, leading to the varied presentation of halos that individuals might experience.
Everyday Reasons for Seeing Halos
Many common factors can cause halos. Bright light sources, such as car headlights at night or streetlights, can naturally cause some light diffraction, making halos a normal visual experience in certain conditions.
Refractive errors, which are common vision problems, can also contribute to halos. Conditions like astigmatism, nearsightedness (myopia), and farsightedness (hyperopia) cause the cornea or lens to be irregularly shaped, leading to light scattering as it enters the eye. This irregular bending of light can result in halos, especially noticeable in low-light environments when the pupil dilates, allowing more light to enter through the distorted areas.
Halos can also be a temporary side effect for individuals recovering from refractive surgery, such as LASIK. The reshaping of the cornea during these procedures can temporarily alter how light is processed, and halos typically diminish significantly within the first few weeks to months as the eye heals. Dirty contact lenses or smudged eyeglasses can similarly cause light to scatter, creating halos due to obstructions on their surfaces. An uneven tear film, often associated with dry eyes, can also distort incoming light and lead to halos because the eye’s surface is not uniformly smooth.
Medical Conditions and Related Treatments
Cataracts, a common age-related condition, involve the clouding of the eye’s natural lens. This clouding causes light to scatter as it passes through, producing halos and glare, particularly at night. Cataract surgery, which involves replacing the cloudy lens with an artificial one, is the primary treatment and can resolve the halos.
Glaucoma, especially acute angle-closure glaucoma, can cause halos and requires immediate medical attention. In this condition, the pressure inside the eye rises rapidly due to a blocked drainage angle, leading to corneal swelling. This corneal edema distorts light entry, resulting in the perception of colored halos or rainbow rings. Treatment typically involves medications to lower intraocular pressure and often a laser procedure to create a new drainage path.
Corneal edema, or swelling of the cornea, from various causes can also lead to halos. This swelling can result from conditions like Fuchs’ dystrophy, eye trauma, or complications from eye surgery, causing the cornea to become hazy and scatter light. Management depends on the underlying cause and may include eye drops to reduce swelling or, in some cases, corneal transplantation. Certain medications, such as some used for erectile dysfunction or antimalarials, can also list halos as a potential side effect.
When to Seek Professional Eye Care
A sudden onset or a noticeable worsening of halos should be evaluated promptly. This is particularly true if halos are accompanied by other symptoms such as eye pain, redness, nausea, or vomiting, as these can be signs of acute angle-closure glaucoma, which is a medical emergency.
Vision changes like significant blurring or vision loss occurring alongside halos also indicate a need for immediate medical attention. If halos persist and cannot be attributed to common factors like bright lights, refractive errors, or temporary post-surgical effects, it is advisable to consult an eye doctor. Regular comprehensive eye exams are important for maintaining eye health and can help detect conditions that cause halos early, especially for individuals as they age or have a family history of eye diseases.