Photochromic lenses are eyeglass lenses that darken in sunlight and lighten in the absence of UV light. They are designed to adjust to the light conditions around you, providing clear vision in various lighting conditions.
The darkening of the lenses is due to a chemical reaction triggered by UV light. The reaction causes the lenses to become darker, reducing the light entering the eye. This protects against glare and harmful UV rays, making photochromic lenses ideal for outdoor activities.
Photochromic lenses are available in single-vision and multifocal designs, including line-free progressive lenses. They can also be made with plastic, polycarbonate, and glass to suit different preferences and needs.
There are two main types of photochromic lenses: those that darken in response to UV and visible light and those that only darken in response to UV light. The latter is known as the "Transition" lens and is the most common type of photochromic lens.
It's important to note that photochromic lenses may not darken in certain conditions, such as inside a car or behind a windscreen that blocks UV light. Additionally, temperature and altitude may affect their darkening and lightning response.
In conclusion, photochromic lenses offer the convenience of clear vision in various lighting conditions. They protect against glare and harmful UV rays, making them ideal for outdoor activities. However, their response may be affected by certain conditions, and it is best to consult an optometrist to determine if they suit you.