The best prescription hiking sunglasses are water resistant, smudge resistant, oleophobic and fog resistant as well. Owing to the fact that hikers sweat a lot, hydrophobic and oleophobic lenses are the best addition to seal the deal. Hydrophobic lenses repel water molecules and therefore, can be great for perspiring hikers.
Hydrophobic surfaces are also anti-static. Dust and other dirtying particles are not attracted to them and sometimes if they do happen to collide, they just fall right off. When they do get dusty and dirty they clean easier than lenses that do not have hydrophobic coatings. Oleophobic hiking sunglasses repel oil and are smudge resistant as well.
When one is at a higher altitude and it’s really windy, one often has a lot of protective gear on themselves. Some have scarfs while others use helmets, when breathing, the hot air might escape and penetrate from under the hiking sunglasses causing fog to pile up.
Prescription hiking sunglasses are often hydrophobic which protects one over fog piling up in the sunglasses. The hydrophobic element in the sunglasses for hiking works in a split of a second. If one gets water on it, it goes away pretty quickly. With the best hiking sunglasses, it will not be an issue when every time one breathes, one can’t see where they’re stepping.