DOES BRIGHT SUNLIGHT CAUSE EYE DAMAGE?

Ophthalmologist Carolina Valdivia, MD answers a question about the impact of bright sunlight on the eyes.

Hi Dr. Valdivia,

A few days ago I had an eye exam with dilated pupils. I was allowed to leave the clinic at about 12 noon with instructions that I should not drive. Where I am, this meant that the sun was absolutely blazing. Under normal conditions, I would have experienced discomfort adjusting to the bright sunlight, let alone with dilated pupils. It was terrible. I did not have sunglasses and neither was I provided sun protection by the clinic, but it was only later on that I became somewhat concerned about this.

I have since found out that it is fairly common for some clinics to allow patients with dilated pupils to leave without eye protection, but many other clinics recommend the use of sunglasses after pupil dilation.

I know that it takes a long time to get general ultraviolet damage, but with such bright sunlight entering my eyes and reflecting off the sidewalk, I would like to know if there is a substantial risk of retina damage from being exposed to such strong midday sun with dilated pupils?

Thank you for your time.



Thank you for your question and for your interest in glaucoma-eye-info.com.

In order to answer your question, a brief explanation of ultraviolet light waves is necessary. Ultraviolet light waves are electromagnetic radiation that is at a wavelength shorter than visible light. This means that the human eye cannot perceive them.

Ultraviolet light waves are present in sunlight. Most people are aware of their effects on skin through having experienced a painful sunburn. However, ultraviolet light waves have other effects on human health, including their ability to cause retina damage.

If you go outside during the day with dilated pupils, too much light enters the eye. This can cause discomfort. You left the office of your ophthalmologist around noon, so the discomfort that you experienced probably was severe. However, this does not mean that you suffered retina damage due to excess exposure to bright sunlight. This is because the exposure was indirect, caused mostly by the reflection of light from the sidewalk and street pavement.

Without sunglasses to help reduce glare and filter bright sunlight, your first reaction upon stepping outside likely was to shut your eyes in response to the discomfort that you felt. Perhaps you even covered your eyes with your hands. This minimized your initial exposure. When you attempted to open your eyes again, you probably did so squinting and looking down to decrease direct-light exposure. Squinting reduces the amount of light entering the eye by constricting peripheral vision. You also might have used your hand to shade your brow. This further minimized your exposure to bright sunlight.

Bright sunlight overloads the cones and photosensitive ganglion cells of the retina, but they recover quickly. However, severe retina damage can occur from exposure to ultraviolet light waves. Fortunately, the eye has its own protection mechanism against ultraviolet radiation. It is located in the colored portion of our eyes known as the iris, which contains melanin pigment. This is the same pigment that gives color to your hair and skin. Melanin is capable of absorbing large amounts of ultraviolet radiation and helps to prevent retina damage from passive exposure to ultraviolet light waves over a lifetime.

There is a condition known as ultraviolet keratitis in which the outermost layer of cells of the cornea are damaged from overexposure to ultraviolet light waves. It can be thought of as a sunburn to the eyes and, like sunburn to the skin, it is often very painful. However, ultraviolet keratitis typically resolves spontaneously within 36-72 hours. In your particular case, the exposure time would have been insufficient to cause ultraviolet keratitis.

There are cases of retina damage occurring when people attempt to observe a solar eclipse directly, rather than use a pinhole camera to view it indirectly. Under normal circumstances the sun is too bright for us to look at it directly. However, during a solar eclipse, light in the visible spectrum diminishes, making it possible to look straight at the sun for sustained periods. It is very dangerous to do this because ultraviolet damage can occur. Ultraviolet light waves are invisible to the human eye and go directly to the retina, causing burns.

Of course, a solar eclipse represents a special case in which the eye can be exposed to large amounts of ultraviolet radiation. This can cause severe damage to the retina. However, in your case, the indirect exposure to light that you experienced after the eye exam, even though it caused discomfort, did not contain sufficient ultraviolet radiation to burn your retina. You can relax.

In the future, I recommend bringing a pair of sunglasses with protection from ultraviolet light waves to your next eye examination. This way you will be absolutely certain that you will not have to suffer through the same discomfort that you did this time with dilated pupils.

Carolina Valdivia, MD

REFERENCE:

Kunimoto DY, Kanitkar KD, Makar MS, Friedberg MA, and Rapuano CJ. The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease, 4th Ed. Philadelphia: Lippincott, Williams and Wilkins, 2004:48-49.

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