Winter is upon us, and certain occupations require a person to go in and out of the cold weather frequently during the day. For eyeglass wearers, this brings on a familiar difficulty. Lens fogging.
Lens fogging occurs when humidity in the air condenses on a frosty cold eyeglass lens. It is an annoyance, but worse, it affects productivity and can be very dangerous. Suppose the eyeglass wearer doesn't see a stairway, other obstacle, or a small child in his path because the eyeglass lenses are fogged white.
The amount of lens fogging can be lessened by
choosing lenses with a low specific heat. Specific heat is a measure of how a material changes temperature. Materials with a low specific heat change temperature more readily. When temperature of the material equilizes with the surrounding air, moisture stops condensing on the lenses, and can begin to evaporate.
But while all that evaporation is finally clearing the lenses, vision is still impaired.
Fortunately, modern optical labs offer an alternative. Anti-Fog coatings are available that have a high surface energy - are hydrophillig (water loving). This allows the condensed moisture to sheet over the lens. The lens surface still gets wet, but the moisture doesn't ball up in droplets and cause fogging.
I wouldn't recommend Anti-Fog coating for year round wear. It is not necessary, and you will get much better vision with Anti-reflective coatings during the nice weather seasons. But as a seasonal pair of eye glasses, specifically for those times when you are going inside from the cold weather, Anti-fog coating can be an important safety feature on eyeglasses.
Situations where Anti-Fog eyeglass coating are recommended:
- Delivery Personnel
- Food Handlers In Walk-In Refridgeration Units
- Pool Personnel
- Police & Emergency Personnel