What Are Transitions Lenses?
"Transitions" are a trademarked name brand.
The actual lens is called a photochromic lens.
When the clear (or almost clear) lens is exposed to direct sunlight it begins to darken.
Depending for how long the lens is exposed to direct sunlight will determine how dark the lens becomes; the longer the exposure the darker.
Photochromic lenses can be added to your prescription eyeglasses with glass, polycarbonate or another highly durable plastic lens.
Glass is typically custom made and will have microcrystalline silver chloride dispersed throughout.
Depending on how thick the glass lens is will determine just how dark it becomes.
Because the glass is already embedded with silver chloride, the lens will never be fully clear.
The photochromic properties in plastic lenses are slightly different.
A plastic photochromic lens relies on organic photochromic molecules to achieve the reversible darkening effect.
Unlike the glass lens, it is applied as a surface layer.
Direct UV light activates and darkens the lens.
The reason they don't darken indoors is because the UV exposure is minimal.
Even when driving, car windows shield and block a decent amount of UV ligh which prevents the photochromic lenses from fully darkening.
Once exposed to direct UV/sunlight, after the first minute the lenses will darken substantially and will continue to darken for fifteen minutes.
The opposite is also true.
Once removed from direct UV/sunlight it will begin to clear immediately.
It will take up to 15 minutes to return to the non-exposed state.
Temperature has an effect when trying to achieve the darkest state of the lens.
The colder the temperature the darker the lens.
In very hot weather the lenses won't reach their darkest state - making these lense better for skiers rather than for beach-goers.
In colder temperatures it will take the lenses longer to return to their non-exposed state.
There are some advantages and disadvantages to having photochromic lenses.
They offer coverage for the different varying degrees of light that people are normally exposed to, they eliminate the need for having a pair of sunglasses (or prescription eyeglasses with tinting) and they absorb 100% of UV radiation which causes macular degeneration.
The downfalls are: it takes awhile for the lenses to reach their potential and then return to their normal state, weather and cloud coverage determine whether the lenses will reach their maximum.
On a cloudy day, the lenses will NOT fully darken due to the lighter UV exposure and the lenses won't fully darken inside of a car due to the minimal UV exposure.
Deciding whether to order glasses with photochromic lenses is a matter of preference and will be determined by how and what you actually use them for.
There are several brands available and it is recommended that you investigate which brands are sold by your optician.
The actual lens is called a photochromic lens.
When the clear (or almost clear) lens is exposed to direct sunlight it begins to darken.
Depending for how long the lens is exposed to direct sunlight will determine how dark the lens becomes; the longer the exposure the darker.
Photochromic lenses can be added to your prescription eyeglasses with glass, polycarbonate or another highly durable plastic lens.
Glass is typically custom made and will have microcrystalline silver chloride dispersed throughout.
Depending on how thick the glass lens is will determine just how dark it becomes.
Because the glass is already embedded with silver chloride, the lens will never be fully clear.
The photochromic properties in plastic lenses are slightly different.
A plastic photochromic lens relies on organic photochromic molecules to achieve the reversible darkening effect.
Unlike the glass lens, it is applied as a surface layer.
Direct UV light activates and darkens the lens.
The reason they don't darken indoors is because the UV exposure is minimal.
Even when driving, car windows shield and block a decent amount of UV ligh which prevents the photochromic lenses from fully darkening.
Once exposed to direct UV/sunlight, after the first minute the lenses will darken substantially and will continue to darken for fifteen minutes.
The opposite is also true.
Once removed from direct UV/sunlight it will begin to clear immediately.
It will take up to 15 minutes to return to the non-exposed state.
Temperature has an effect when trying to achieve the darkest state of the lens.
The colder the temperature the darker the lens.
In very hot weather the lenses won't reach their darkest state - making these lense better for skiers rather than for beach-goers.
In colder temperatures it will take the lenses longer to return to their non-exposed state.
There are some advantages and disadvantages to having photochromic lenses.
They offer coverage for the different varying degrees of light that people are normally exposed to, they eliminate the need for having a pair of sunglasses (or prescription eyeglasses with tinting) and they absorb 100% of UV radiation which causes macular degeneration.
The downfalls are: it takes awhile for the lenses to reach their potential and then return to their normal state, weather and cloud coverage determine whether the lenses will reach their maximum.
On a cloudy day, the lenses will NOT fully darken due to the lighter UV exposure and the lenses won't fully darken inside of a car due to the minimal UV exposure.
Deciding whether to order glasses with photochromic lenses is a matter of preference and will be determined by how and what you actually use them for.
There are several brands available and it is recommended that you investigate which brands are sold by your optician.