It should be the first diagnosis ruled out when sickness occurs while ascending to a high altitude. Prevention
HACE is generally preventable by ascending gradually with frequent rest days while climbing or trekking. Not ascending more than 1,000 metres (3,300 ft) daily and not sleeping at a greater height than 300 metres (980 ft) more than the previous night is recommended. The risk of developing HACE is diminished if acetazolamide or dexamethasone are administered. Generally, the use of acetazolamide is preferred, but dexamethasone can be used for prevention if there are side effects or contraindications. Some individuals are more susceptible to HACE than others, and physical fitness is not preventive. Age and sex do not by themselves affect vulnerability to HACE. Treatment
Patients with HACE should be brought to lower altitudes and provided supplemental oxygen, and rapid descent is sometimes needed to prevent mortality. Early recognition is important because as the condition progresses patients are unable to descend without assistance. Dexamethasone should also be administered, although it fails to ameliorate some symptoms that can be cured by descending to a lower altitude. It can also mask symptoms, and they sometimes resume upon discontinuation. Dexamethasones prevention of angiogenesis may explain why it treats HACE well. Three studies that examined how mice and rat brains react to hypoxia gave some credence to this idea.If available, supplemental oxygen can be used as an adjunctive therapy, or when descent is not possible.
It can also occur due to using tanning beds without proper eyewear. Natural sources include bright sunlight reflected from snow or ice or, less commonly, from sea or sand. Fresh snow reflects about 80% of the UV radiation compared to a dry, sandy beach (15%) or sea foam (25%). This is especially a problem in polar regions and at high altitudes, as with about every 300 m (1,000 ft) of elevation (above sea level), the intensity of UV rays increases by four percent. Diagnosis
Fluorescein dye staining will reveal damage to the cornea under ultraviolet light. Prevention
Photokeratitis can be prevented by using sunglasses or eye protection that transmits 5–10% of visible light and absorbs almost all UV rays. Additionally, these glasses should have large lenses and side shields to avoid incidental light exposure. Sunglasses should always be worn, even when the sky is overcast, as UV rays can pass through clouds.The Inuit, Yupik, and other Arctic peoples carved snow goggles from materials such as driftwood or caribou antlers to help prevent snow blindness. Curved to fit the users face with a large groove cut in the back to allow for the nose, the goggles allowed in a small amount of light through a long thin slit cut along their length. The goggles were held to the head by a cord made of caribou sinew.In the event of missing sunglass lenses, emergency lenses can be made by cutting slits in dark fabric or tape folded back onto itself.