Sunglasses

Sunglasses - Learning Objectives

Photokeratitis.
Why sunglasses are important.
Testing for UV protection.

Mammoth Mountain Ski Slope

Too young for sunglasses in the early 1960s, I had spent that Spring day skiing on the bright sunlight slopes of Squaw Valley California. Slathered with Sea & Ski, the original sunblock that my mother gave us to put on our faces, eye protection from the Sun had yet to be recognized as important for children. At my age, of perhaps eleven years, I was allowed to spend the day skiing various mountain ranges with my father's best friend's daughter, a skier my same age. I need to send her this and find out if she too experienced a traumatic four-hour car ride home that evening from the sides of the slopes.

First I noticed my vision going kind of grey and yet it was still fairly bright outside, the sun had not even set. Next I noticed some kind of headache thing behind my eyes and on the sides between my eyes and my ears. These annoying sensations were followed by the alarming sense of the world going dark. Within an hour, almost black, the intensity of the experience was one that made me not want to open my eyes.

My wise parents understood that the brightness of the snow had doubled the intensity of the sunlight reaching my eyes and after an entire day of staring at the white reflective slopes, the effect was of "temporary" snow blindness.

Alarming as this may sound, I remember being at piece with the thought that it will probably all go away by tomorrow morning and quietly fell asleep in the backseat of the Buick Riviera driving back, like we did every weekend, from Lake Tahoe to our Bay Area home.

Reassured by the return of my sight in the morning, by age 12 and the next ski season, I had purchased my first pair of sunglasses.
By Trish Odenthal

Photokeratitis - Snow Blindness

According to the American Association of Ophthalmologists, not only snow, but ice, water and sand can be highly reflective and damage our eyes. The damage may be temporary or lead to more permanent conditions such as cancer and cataracts.

Snow can double your UV exposure.

UV 254 nm Reflectance from different materials - How is UV reflection different from Visible Light reflection? "Many surfaces reflect UV radiation and add to the overall UV levels you experience. While grass, soil or water reflect less than 10 per cent of incident UV radiation, sand reflects about 15 per cent, and sea foam about 25 per cent. Fresh snow is a particularly good reflector and almost doubles a person's UV exposure. Recurring incidences of snow blindness or photokeratitis in skiers emphasize that UV protective measures must take ground reflection into account." World Health Organization
https://www.who.int/news-room/q-a-detail/ultraviolet-(uv)-radiation
And
https://www.ccohs.ca/oshanswers/phys_agents/ultravioletradiation.html

Sunglasses

UV - why is it important?

Ophthalmologists recommend that you wear 99 percent and higher UV (ultraviolet radiation)-absorbent sunglasses and a brimmed hat whenever you are in the sun for long periods of time. Proper sunglasses are key to protecting your eyes from sun-related damage, and they should be worn anytime you are outdoors, particularly under these circumstances:

During the summer, when the level of ultraviolet radiation (UVA and UVB) is at least three time higher than during the winter;
When at the beach or in the water;
When participating in winter sports, especially at high altitudes;
When using medications that can cause sensitivity to light (photosensitivity).

The best sunglasses offer 100 percent UV absorption, are of the best optical quality and are impact resistant. [1]