Visual halos are bright circles or rings of light around illumination sources, often noticeable in low-light conditions. While various factors can cause halos, their appearance can sometimes indicate an underlying eye condition, such as glaucoma.
Describing Glaucoma Halos
Halos associated with glaucoma, particularly acute angle-closure glaucoma, often appear as rainbow-colored rings around lights. These halos can be accompanied by symptoms, including sudden blurred vision and intense eye pain. Individuals might also experience headaches, nausea, or vomiting alongside these visual disturbances. Such a combination of symptoms can signal a medical emergency requiring immediate attention.
Why Glaucoma Leads to Halos
Glaucoma is a group of eye conditions that damage the optic nerve, often due to elevated pressure inside the eye, known as intraocular pressure (IOP). In acute angle-closure glaucoma, the eye’s drainage system can become blocked, leading to a rapid increase in this internal pressure.
This sudden rise in IOP can cause the cornea, the clear front surface of the eye, to swell. Corneal swelling disrupts the cornea’s normal transparency and smoothness. As light passes through the swollen, irregular corneal tissue, it scatters instead of focusing sharply on the retina. This scattering of light causes colorful halos around light sources.
Other Reasons for Seeing Halos
Halos are not exclusively a symptom of glaucoma and can arise from several other conditions or circumstances. For example, cataracts, which involve the clouding of the eye’s natural lens, are a common cause, as the cloudy lens scatters incoming light. Dry eye syndrome can also lead to halos because an insufficient tear film or an irregular eye surface can cause light to scatter. Individuals who have undergone LASIK surgery may experience temporary halos as the cornea heals and adjusts to its new shape.
Wearing certain types of contact lenses can also result in halos, particularly if the lenses cause corneal swelling due to a lack of oxygen or if the pupil dilates beyond the optical zone of the lens. Astigmatism, an irregularly shaped cornea, can bend light in unusual ways, leading to halos, especially at night. Fuchs’ dystrophy, which causes the cornea to swell, can also manifest with halos.
When to Consult an Eye Doctor
Any new or persistent visual halos warrant a prompt eye examination by an eye care professional. This is particularly important if halos are accompanied by symptoms such as eye pain, a severe headache, nausea, or sudden vision changes like blurring or loss. These symptoms, especially when appearing suddenly, can indicate acute angle-closure glaucoma, a medical emergency. Timely diagnosis and treatment are important to prevent potential permanent vision damage. Regular eye exams are valuable for detecting eye conditions, including various forms of glaucoma, before significant vision loss occurs.