What causes you to see halos and glare?
Seeing halos around lights at night or glare from the headlights of oncoming cars is often caused by refractive errors. Which means your eyes don’t refract or “bend” light correctly. This happens when you have an astigmatism, nearsightedness, or farsightedness.
In these refractive errors either your cornea or lens is not the correct shape to properly bend the light, so that it precisely strikes your retinas, the light-sensitive layer at the back of the eye.
To create vision, light passes through the pupil to the lens behind it, then the lens also bends and focuses the light a second time. The light then passes through the clear, gelatinous substance that fills the eyeball, called the vitreous, then it reaches the retina. So refractive, “bending” errors can happen in many places along the way.
In addition, at night the pupils dilate to allow in more light and this allows more peripheral light to enter the eyes and this can cause glare and halos around lights.
Besides refractive errors, other conditions can cause halos and glare around lights.
Dry Eye Syndrome
Dry eye syndrome is a condition in which the eyes are chronically dry. The tear film of the eyes lubricates and provides a refracting surface for light based on the index of refraction between air and the tear film. Dry eyes not only feel uncomfortable, but can cause visual disturbances such as blurred vision, fluctuating visual acuity, and glare and light sensitivity.
Seeing halos around lights is a common side effect of LASIK surgery and is usually not a cause for concern. The halos typically disappear after a few weeks.
Cataracts Commonly Cause Halos and Glare
Seeing halos around lights is a common symptom of cataracts. When the lens becomes cloudy it bends light in an unusual way and scatters it as it enters the eye, and this is what causes the halos and glare around lights. Cataract surgery to replace the cloudy lens can also cause halos around lights, but this side effect will diminish as the eye adjusts to the new lens.
Fuchs’ dystrophy is a progressive fluid buildup in the cornea of the eye causing the cornea to swell and thicken. This can lead to glare and blurred and cloudy vision. In advanced cases, a cornea transplant is needed to restore vision.
Glaucoma causes damage to the optic nerve, usually due to elevated pressure within the eye. Seeing halos around lights can be an early sign of acute-angle glaucoma, which is considered a medical emergency. If you have a sudden onset of seeing halos around lights, along with headache, vomiting, blurred vision, eye pain or weakness, seek immediate medical care.
Kerataconus causes the cornea to progressively thin and take on a cone-like shape. This condition causes visual impairment and may cause the appearance of halos around lights. In mild cases glasses or rigid gas permeable contacts will correct the visual impairment, but in advanced cases a corneal transplant may be needed.
This is caused by being exposed to too much of the sun’s ultraviolet (UV) light. In layman’s terms it is “sunburned eyes”. This can cause pain, sensitivity to light, headache, and blurred vision. The symptoms usually go away without treatment within a day or two. If they don’t, or the eye pain is severe, see a doctor.