A study of snow blindness
by Henrik Forsius, Professor Emeritus of Ophthalmology, Helsingfors
For those who plan to climb to the top of Mount Everest, remembering sunglasses as protection against snow blindness is recommended. We know that many arctic populations, among them the Inuits (Eskimos), have for thousands of years used different kinds of spring equipped-glasses or shields made of bone to protect their eyes against snow blindness. Such primitive equipments can now be found in museums. Already in 1911, Norman-Hansen wrote that the Eskimos had long since adopted the use of conventional sunglasses.
Snow blindness, or at least an eye affection, that resembled snow blindness, was described by Xenophon, in Anabasis, also known as the Persian Expedition. St.Yves had in the 18th century the honour of being the first to introduced snow blindness or photokeratopathy, as it is now mostly called in the medical literature. The Swedish ophthalmologist Widmark discovered that the photokeratopathy is caused by UV light.
It was at first difficult to understand why snow blindness is such a severe problem in the arctic, as UV light in Lapland in the winter and spring is quite limited, only 10-20% of that in Southern Finland, where snow blindness does not cause problems.
UV light reflected from snow is the cause of snow blindness. But why is UV light so dangerous in the arctic? We also have snow in other parts of Finland as well as in the Baltic countries, but with few exceptions, no snow blindness. Such exceptions are reported for seal hunters, who travel on the ice in the northern part of the Botnian Gulf, and for fishermen on the lakes and rivers in Lapland.
The explanation is that in the arctic and in the Alps the sky is free of dust and moisture. I have read reports that arctic explorers have been snow-blinded even at a sun elevation as low as 12 degree. The situation is especially dangerous, if the explorer thinks that a light cloud cover will resorb the UV light. For the explorer, it may also be tempting to take off the sunglasses while engaged in hard physical work.
The symptoms of sun blindness are well known to all ophthalmologists. They are the same as those seen in welders and the treatment is also the same. But if you were alone in the arctic and became blind for a week or even for a few days, the situation could be really dangerous.
Good advice for those who spend holidays on the shores of Southern Europe or Africa: avoid suntanning during the mid-daylight hours. Instead, sunbathe during the first three hours after sunrise or before sunset, the dusty atmosphere absorbs nearly all UV light when the sun is below an elevation of 30 degree.
Animals, living in the arctic can not avoid snow blindness. Nordenskiöld observed this in hares and Kennedy in dogs. Even seals can be snow blind, but not birds, even flying beyond an elevation of 5000 mets. Chickens have been shown to receive very large doses of UV light at 254 nm, the most critical wavelength.
Very little has been written about snow blindness in Northern Scandinavia, i.e. about its occurrence among the Sames (Lapps) and their use of snow-glasses. We know that when the Sames have taken part in polar expeditions, such as in Nordenskiöld´s wellknown expeditions, they have encountered the same problems as the other participants, including snow blindness and painful watering eyes for several days. We therefore decided to study this problem.
A Finnish social worker, T. I. Itkonen noted that in earlier times the Sames used urine and breast milk as treatment against snow blindness.
Snow blindness is caused by an acute overdose of UV light. Another very common, but little known form of photokeratopathy , the chronic photophtalmia, was first described by Lugli (1935) in Italy and by Freedman (1965) from Northern Canada. The initial sign is superficial degeneration medially and laterally in the limbus of the cornea, this has been described worldwide in outdoor people.
In such populations as the Inuits and Lapps, the degeneration can cause partial central opacification in the cornea. People, living in tropical regions with white coral shores, as along the Red Sea, can even be blinded by bandkeratopathy, the end-stage of photokeratopathy. I have studied and noted this sign in many places; at a 4000 met elevation near lake Titicaca, in the Himalaya region, in Hawaii and in the desert region of Tunisia. In addition, I have noted the occurrence of pterygium and of pinguecula, both signs, witch more or less caused to some extent by the climate.
The eyes can also be injured by wind and cold. A combination of these causes excessive tearing, known as epiphora, in skiing competitions.
That the cornea can survive freezing is known by all transplantation surgeons, but also found in the literature is, that in extreme cases prolonged freezing in arctic surroundings can lead to severe eye injuries.
I asked P. Tuomaala, who has worked for more than 20 years as an eye-doctor in Rovaniemi, the most northerly situated eye hospital in Finland, if he had treated patients with snow blindness. He told me that earlier he had treated five or six patients annually, but within the last few years only a couple of patients, mostly of them tourists.
In 1966-1970, Aldur Eriksson and I studied altogether 687 Scolt-Sames in Northern Finland.
The Scolt-Sames are the most easterly residing Sames in Northern Finland, living around Lake Enare. Their main occupation is reindeer breeding.
We asked them whether they had experienced snow blindness and whether the had used sunglasses or any other kind of protection against the intensive sun during the spring. We were especially interested in whether they used glasses when working with the reindeers on the Lappish hills.
Sunglasses were quite popular, with more men (47.3%) than women (32.5%) using them, leading us to think that they were mostly used for protection against UV light and not to merely be fashionable.
Of the men 23.6% had been snow blind versus only 9.3% of the women. Although women participate in reindeer breeding, the main occupation for this population, children and housework take up the majority of their time.
Some individuals may be more susceptible to snow blindness than others, as evidenced by several men becoming snow blind, while others in their company remained unaffected.
We also studied the occurrence of the other, aforementioned factors caused by the climate, i.e. pinguecula, photokeratopathy and pterygium. The frequency of these factors was high among those, who had been snow-blinded, but not higher, than among other reindeer herders. We therefore got the impression that snow blindness is mostly the result of carelessness. With proper use of simple commercial sunglasses, this problem can be avoided also in the hills in Northern Finland. Compared with the Inuits (Eskimos), snow blindness is thus for the Sames a minor problem.