Photokeratitis: snow blindness

Photokeratitis, also known as photoconjunctivitis, bow eye or snow blindness is an eye condition caused by overexposure to ultraviolet (UV) rays. Such rays can come from an artificial source, from the sun, or from its reflection on snow, white sand, water, or ice.

It is called snow blindness because water in that state enhances its reflective capacity: it reflects 80% of the ultraviolet rays that fall on it. Likewise, in high areas the air is less dense and this reduces protection against UV rays.

Why does photokeratitis occur?

Snow blindness is the most common form of photokeratitis, but not the only one. Any overexposure to UV rays can cause this disease. However, it is more common in people who live near the poles or in high mountains. The proportion of ultraviolet radiation increases by 10% for every 1000 meters of altitude.

Photokeratitis is, simply put, a burn of the cornea. This is the transparent tissue that covers the eye and is shaped like a dome. The outermost layer is the epithelium and it is a very sensitive tissue, which becomes irritated and inflamed when too much UV light reaches the eye.

Snow blindness can cause temporary loss of vision. It is also produced by severe freezing or drying of the epithelium. This occurs when a person is exposed to excessively dry and cold weather, such as that prevalent in snowy places.

In places with a lot of snow there is an intense reflection of UV rays that affects the eyes.


The main symptoms of photokeratitis are alterations in vision and severe pain in the eyes.. This gradually worsens and as time passes other annoying manifestations appear.

Photokeratitis comprises three phases. In the first there is only an alteration of vision, similar to a glare. It is at this point that there is still no eye injury.

In the second phase, the main symptom is photophobia or rejection of light. Any lighting bothers more and more and a sensation appears as if you had grit in your eyes, especially when blinking. There is already involvement in the cornea.

The third phase is characterized by severe pain and irritation. Manifestations such as the following also appear:

  • Tearing
  • Red eyes and swollen eyelids.
  • Vision blurred and with halos.
  • Very sensitive to bright light.
  • Spasms in the eyelids.
  • Headache.
  • Decreased visual acuity and changes in color perception.

Read also: What are the causes of watery eyes?

Treatment of photokeratitis

Photokeratitis or snow blindness usually resolves on its own in 24 to 48 hours. If symptoms appear, it is best to remove contact lenses if they are used, as these can aggravate the situation. It is not advisable to rub your eyes either.

Some measures to which it is possible to go are the following:

  • Apply a cold compress to the eyes. This helps to relieve pain and burning.
  • Moisturize the corneas. This can be done with artificial tears and usually speeds healing.
  • Avoid exposure to light.
  • Use over-the-counter pain relievers for headache.

In case the symptoms become very severe or persist for more than two days, it is necessary to consult with the ophthalmologist. Specialized care may be needed, either because of the severity of the photokeratitis or because there is an additional problem.

How to prevent it?

Preventing photokeratitis is very simple: a few basic measures are enough. The first and most important is to wear polarized sunglasses, since they reflect the sun's rays and protect from ultraviolet radiation.

What is indicated is that these glasses meet the following characteristics:

  • They must be approved by ISO standards and display the CE mark.
  • The most suitable filter is grade 4.
  • The more closed, the better, since they reduce side reflections.
  • If the quality of the glasses is uncertain, it is best to consult an eye doctor for an examination.

On the other hand, photochromic glasses can also be a great option. When a person suffers from dry eye, it is best to moisten with artificial tears periodically. Protecting the head with a hat or cap also helps.

Not only in the snow, but protection should be used at all times of sun exposure.

Discover more: Home remedies for sunburn

Photokeratitis is not only due to snow

As already mentioned, photokeratitis is more common in places where there is snow or at high altitude. But nevertheless, the most correct thing is to protect the eyes at all times and places. That is why it is advisable to wear sunglasses, even on cloudy days and despite not being in contact with the snow.

Snow blindness rarely causes serious complications. However, it is a very painful disease that becomes disabling for a couple of days. Tanning lamps and beds, as well as arc welding, can also cause this condition.