What Are Photochromic Lenses?
Photochromic lenses are one of your options when selecting eyeglasses. These lenses get darker in color when exposed to the sun or other sources of UV light.
Other names for photochromic lenses include:
- Transition lenses
- Light adaptive lenses
- Variable tint lenses
What Are Photochromic Lenses Used For?
Photochromic lenses are ideal for people who need to wear glasses all the time. The two main purposes of photochromic lenses are to protect your eyes from UV light and to eliminate the need for a separate pair of prescription sunglasses.
The lenses offer complete protection from UVA and UVB rays at all times. This feature doesn’t depend on whether the lenses are clear or dark at any given moment.
UVA and UVB rays are the two types of UV light that can get through Earth’s atmosphere. They’re the main types that should concern you when it comes to your health.
How Can UV Light Damage Your Eyes?
You’re repeatedly exposed to UV light throughout your lifetime, mainly in the form of sunlight. Over the course of your life, UV light can damage your eyes and the skin that surrounds them. This means that it’s important to protect your eyes by using products like photochromic lenses.
The types of eye damage that repeated UV exposure can lead to include:
Cataracts. The lenses in your eyes become cloudy and increasingly more opaque with this condition. Cataracts eventually lead to blindness. You need surgery to treat this condition.
Macular degeneration. This is a major cause of blindness in people who are older than 55. It’s the result of accumulated eye damage throughout your lifetime. There currently isn’t a cure.
Corneal damage. Your cornea is crucial for proper vision. UV lightwaves can particularly damage this part of your eye.
Skin damage. The skin surrounding your eye is vulnerable to UV damage as well. Examples of skin problems caused by UV include dryness, wrinkles, a loss of elasticity, and mottled pigmentation.
Certain cancers. UV light interferes with the base pairs that make up your DNA. This leads to mutations that could cause cancer. Squamous cell carcinomas are an example of a type of cancer that can invade your eye. Over time, this type of cancer can lead to the surgical removal of your entire eye.
How Do Photochromic Lenses Work?
Photochromic lenses have been around since the 1960s. The technology has changed a lot since then, but the fundamental principles remain the same.
In general, these lenses work by using chemical reactions that are triggered by UV exposure. The result of the chemical reaction is a color change in the lens.
The very first photochromic lenses were made of glass and coated with silver chloride and silver halide, among other molecules. When exposed to UV light, these compounds triggered a chemical reaction that darkened the lens. The reaction reversed when the UV light was gone, making the lens clear again.
Today, the lenses are made from several different materials. Proprietary photochromic dyes are added to these materials in many ways. The molecules within these dyes undergo color changes at different rates when exposed to UV light.
The lenses darken in proportion to the amount of UV light they receive. This means that the brighter it is in your environment, the darker your lenses become.
What Are Photochromic Lenses Made Of?
These days, glass lenses are far less common than newer synthetic materials. Most lenses are made from some type of plastic or resin. The reason for this transition is that resins tend to be lighter and sturdier than glass. They’re also harder to scratch and easier to evenly coat or infuse with the photochromic molecules.
There are many ways to produce resins and infuse them with the necessary dyes. This makes them a more flexible material to work with compared to glass.
There are a variety of brands of photochromic lenses to choose from. Different brands make their lenses from different base materials and dyes. So even though all photochromic lenses work in almost the same way, the variations in materials alter the characteristics of the lenses, including their rate of color change.
The frames for your lenses can come in all types of materials, including metal and plastic.
Types of Photochromic Lenses
Today, there is a wide variety of photochromic lenses on the market. You can get them in an array of styles designed to fit your needs. Examples include:
Sports eyewear. Only certain types of eyewear are safe to use during athletic events. These include polycarbonate and Trivex materials. Transition lenses are available in both varieties.
Coated lenses. Photochromic lenses don’t interfere with the particular types of coating that people like to have on their lenses. For example, anti-reflective coatings help lessen glare and are good for night driving. Water-repellant treatments prevent your lenses from misting over when you move from the cold outdoors to warm indoor environments.
Colorful lenses. Traditional photochromic lenses were only available with a gray tint. But normal sunglasses can come in a wide range of colors. These days, you can get photochromic lenses that are brown or green. The range is still not as broad as for traditional sunglasses, so they may not be available in your preferred color.
Bifocal, multifocal, and high-index options. Certain lenses are designed to deal with particular vision problems. Photochromic lenses are available for most common types of vision-correcting eyewear. For example, bifocal versions help people who have a hard time seeing both far away and up close. High-index options are helpful for people who need strong prescriptions.
Photochromic Lenses Pros and Cons
Like most things, there are positives and negatives when it comes to photochromic lenses. Here’s what you need to know.
Pros of photochromic lenses
Convenience and uninterrupted UV protection. You don’t have to remember to grab your prescription sunglasses when heading outside.
Harder to lose. You’re less likely to lose glasses when you don’t have two pairs to keep track of.
Lots of options. They’re available in many styles and colors, and can meet the prescription needs of most people. If you need shatter-resistant lenses, bifocals, progressives or have other specific needs, there’s almost certainly a photochromic lens for you.
Cons of photochromic lenses
They’re not created equal. Photochromic lenses darken and lighten to varying degrees depending on the brand. Some lenses also take longer than others to adjust to brightness.
Cost. Photochromic lenses tend to be costlier. But they likely cost less than buying a separate pair of prescription sunglasses along with your normal glasses.
Inability to control their transition. You can’t control when the lenses transition. It simply depends on the amount of UV light they’re exposed to. This can be a problem in places with bright fluorescent lights, which can cause your lenses to transition even though you’re indoors. The opposite problem can happen when you’re driving. Windshields are designed to block out UV light, so the lenses might not transition inside a car even when you want them to. But some are designed to help solve this problem.
Temperature effects. Colder temperatures cause some photochromic lenses to transition more slowly than normal. This can be frustrating in the winter.
Blue light protection. These lenses do offer protection from blue light as well as UV light. This isn’t true for all lenses. Blue light comes from sources such as phones and computer screens and is a common cause of digital eyestrain.
Takeaways
Photochromic lenses change to a darker color when exposed to the sun or other sources of UV light. Repeated UV exposure can damage your eyes. The two main purposes of photochromic lenses are to protect your eyes from UV light and to eliminate the need for a separate pair of prescription sunglasses. In general, these lenses work by using chemical reactions that are triggered by UV exposure.
FAQs About Photochromic Lenses
Is photochromic better than polarized?
Neither is better than the other. It just depends on your needs. Polarized lenses block light reflected off surfaces, which can be helpful when driving or doing other outdoor activities.
Which is better: anti-blue light or photochromic?
Most, if not all, photochromic lenses also provide blue light protection.
What is the lifespan of a photochromic lens?
About two to three years, but it varies based on the maker of the lens. When they start to decline, they won’t darken as quickly or get as dark and can sometimes take on a yellowish hue.
