How to choose the right sunglasses for mountaineering and mountain tourism?
The main functions of sunglasses are to protect the eyes from bright light and ultraviolet radiation, as well as from possible mechanical damage. They will not be superfluous for any long-term outdoor activities, but when it comes to hiking and climbing, especially in the highlands, eye protection is simply necessary. With increasing altitude above sea level, the intensity of UV rays increases, add to this almost 80 percent reflectivity of sunlight from snow and we get a high risk of retinal burns and so-called “snow blindness”.
Learn more about types of glasses
So, let’s look at everything in more detail. Ultraviolet is invisible to the human eye, emitted by the Sun, light that has a shorter wavelength than violet – from 180 to 380 nm. In small doses, it causes tanning, and in large doses, it damages the body’s cells, primarily the most sensitive to light – the retina. There are three types of UV radiation: UVA with a wavelength of 315-380 nm, UVB 280-315 nm and, the most dangerous for living organisms, UVC 180-280 nm.
Currently, the most common glasses have protection classes UV-380 and UV-400 – the first is quite enough for reliable protection, and UV-400 will protect with a reserve. Such marking can be trusted only by well-known certified manufacturers. The biggest mistake that can be made when choosing glasses is to take a fake with darkening, but questionable protection from UV – even more harmful ultraviolet radiation will get into the dilated pupil than if you do not wear any glasses at all.
According to the degree of protection from sunlight, glasses are conventionally divided into classes from 0 to 4.
- Grades 1-2 include glasses with slightly tinted glasses, including glasses with yellow and orange lenses. Suitable for cloudy weather, the constant requirement is protection from ultraviolet radiation.
- Category 3 glasses block light up to 92-88% and are the optimal choice for hiking.
- Category 4 allows 3-7% of sunlight to pass through and is used by pilots, welders and metallurgists – suitable for people with sensitive eyes for prolonged exposure to bright sunlight.
Still, it is advisable to have several glasses or replacement lenses for different conditions.
Design Features of Hiking Goggles
All sports and hiking glasses should protect the eyes from all sides. This can be done with a “streamlined” lens shape that extends beyond the edges of the face, or in the form of side curtains made of leather or polymer materials. The choice of design depends only on your convenience when trying on. In any case, the glasses should fit tightly to the face, leaving no gaps for light, and at the same time have space for ventilation.
When hiking, you will often need to take off your glasses for a short time, so it is highly desirable that they have an elastic band or strap.
In winter hikes and ascents, you can replace glasses with a ski mask. It will protect you from bright light and ultraviolet radiation just as well (with proper quality, of course), and will also help protect your face from cold wind and snow. Masks with a flexible two-layer visor and a soft foam pad around the perimeter are best suited.
The following materials can be used to make glasses:
- glass – It itself provides good protection against ultraviolet radiation and is scratch-resistant, but is now almost never used due to the inconvenience of manufacturing lenses of complex shape, their large mass and fragility.
- polycarbonate – the most common material, has excellent mechanical strength, is elastic, lightweight and inexpensive. Among the disadvantages – it is easily scratched and not very durable.
- high-tech polymers (NXT, trivex) – are used in professional models, have better optical properties compared to polycarbonate and are free from the disadvantages of previous materials.
Polarized and photochromic glasses
Polarized glasses are able to remove glare from water, snow and other surfaces. It is worth paying attention to them if you are going on a full ice and snow or water trip.
Photochromic lenses change the degree of darkness depending on the degree of UV radiation. It should be noted that the brightness of visible light and UV do not always coincide, so a situation may arise when photochromic glasses are darkened in cloudy weather and fog. And the change in “brightness” of such glasses takes from 10 to 30 seconds. Based on all of the above, photochromic glasses are not so relevant for mountain hikes.
Let’s sum it up. The right sunglasses will be marked UV-380 or UV-400, have no side gaps for light, sit comfortably on the head, and provide adequate protection from the sun. And most importantly, they should be from a well-known manufacturer and bought not at a market, but at an optician or sports equipment store.