Snow blindness belongs to ophthalmologic ophthalmia, and is an ocular surface tissue reaction caused by shortwave ultraviolet (wavelength 380-295 nm) irradiation. Because of the thin air in the mountains, the mountaineers are unable to filter ultraviolet rays in the sunlight, and they are white ice snow or sand and strongly reflect ultraviolet rays, which cause eye burns. The cornea is the part that is most susceptible to UV burns, and its surface can become uneven and grow blisters. If you continue to be exposed to ultraviolet radiation at high altitudes, the lens inside the eye may also be burned.
The general incubation period after ultraviolet radiation on the eye is 6 to 8 hours, and the onset can be as short as 30 minutes. There were no symptoms at the beginning, and corneal damage had already occurred when symptoms appeared. Symptoms mainly include dry eyes, shyness, tearing, foreign body sensation in sand, severe pain, eye pain, skin redness, conjunctival hyperemia and edema, pupil convulsive contraction, and superficial corneal spotting. The eyes can be very painful. Symptoms usually last 6 to 8 hours, and they usually subside within 24 to 48 hours. Multiple repeated exposures can cause chronic blepharitis and conjunctivitis, and even corneal degeneration, affecting vision.
Snow blindness prevention measures:
Goggles! ! ! Especially with sun visor polarized goggles or metal oxides such as iron, cadmium, cobalt, antimony and other mineral glass snow mirror effect is better. Goggles suitable for use in high altitude environments must be able to filter more than 90% of the UV light. In emergencies, simple slit goggles can be made from cardboard or wood (see figure below).
Snow blindness treatment measures:
(1) Pain relief, topical anesthetic, and eye ointment. You can also acupuncture four white, Hegu, Neiguan acupuncture points. The purpose is to ease the symptoms.
(2) Eye protection (to prevent continued or re-injured). Wear goggles immediately after onset.
(3) Remove contact lenses to reduce corneal irritation and infection.
(4) Apply sterile cotton cloth to the eyes. The above treatment must be continued for 24 to 48 hours until the eye irritation completely disappears. Timely prevention and treatment generally do not leave eye sequelae. Visual acuity is not affected after recovery.
Eye symptoms of mountain sickness usually manifest as blurred or diminished vision. Sometimes there is a 6% reduction in visual acuity at 2800m above sea level, and a 12% decrease over 3600m. At the same time, there is a decrease in dark adaptive capacity. These symptoms can persist for more than 4500m above sea level. Visual fatigue, diplopia, loss of stereo vision, and visual reaction time prolongation can also occur, and the error rate increases significantly, and there are visual illusions. The deterioration of these advanced visual functions can be quickly restored after the altitude is reduced or sufficient oxygen is supplied.
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