Photochromatic lenses

ARAVIND EYE CARE SYSTEMARAVIND EYE CARE SYSTEM

Photochromatic lensesPhotochromatic lenses

R.D.GopinathR.D.Gopinath

Supervisor – Optical SalesSupervisor – Optical Sales

Aravind Eye HospitalAravind Eye Hospital

A R A V I N D E Y E C A R E S Y S T E MA R A V I N D E Y E C A R E S Y S T E M

Introduction Introduction

PC lenses are darkens and lightens automatically when PC lenses are darkens and lightens automatically when

exposed to different exposed to different (UV)(UV) sun light intensities. sun light intensities.

The rate of darkening depends on the ambient temperature. The rate of darkening depends on the ambient temperature.

Available in glass /plastic ; either brown or gray in color. Available in glass /plastic ; either brown or gray in color.

All photochromic lenses block 100 % of the harmful UVrays.All photochromic lenses block 100 % of the harmful UVrays.


HistoryHistory

The term photochromic refers, The term photochromic refers,

changing color – changing color – chroma ; chroma ; in response to lightin response to light -- photo - photo -

First Glass lens developed by corning in 1960.First Glass lens developed by corning in 1960.

Photolite lens sold in the early 1980’s by American optical corporation.Photolite lens sold in the early 1980’s by American optical corporation.

Standard plastic lens by transition optical in 1991.Standard plastic lens by transition optical in 1991.

Early photochromics were strictly glass lenses, but today,regular plastic, Early photochromics were strictly glass lenses, but today,regular plastic,

polycarbonate and high-index glass and plastic. polycarbonate and high-index glass and plastic.


Process Process Glass lenses achieve their photochromic properties Glass lenses achieve their photochromic properties

through the embedding of microcrystalline silver halides.through the embedding of microcrystalline silver halides.

Plastic lenses rely on organic photochromic molecules Plastic lenses rely on organic photochromic molecules

(for example oxazines and naphthopyrans) to achieve the (for example oxazines and naphthopyrans) to achieve the

reversible darkening effect.reversible darkening effect.


Photochromic lensPhotochromic lens

Temperature sensitive & good UV absorbent lens. Temperature sensitive & good UV absorbent lens.

Fully-darkened lens are best UV absorbers. Fully-darkened lens are best UV absorbers.

Also known as Also known as transition or sun-sensitivetransition or sun-sensitive lenses lenses

Not become completely clear in indoors.Not become completely clear in indoors.

Available in gray, brown and pink colors. Available in gray, brown and pink colors.


Color changes in PC lensColor changes in PC lens

Occurs depends on the intensity of UV light.Occurs depends on the intensity of UV light.

Converts silver ions to elemental silver, when short-wave Converts silver ions to elemental silver, when short-wave

length light (300-400nm) interacts.length light (300-400nm) interacts.

Similar process like photo -film is exposed to sunlight.Similar process like photo -film is exposed to sunlight.

Silver halide micro crystalSilver halide micro crystal is responsible to get is responsible to get

darken within a minute by absorb darken within a minute by absorb 80% of incident light 80% of incident light

lighten by absorb about 2lighten by absorb about 20% of incident light 0% of incident light in about 3 in about 3

minutes.minutes.


Photochromic LensesPhotochromic Lenses Ideal for people who don’t want to switch between prescription Ideal for people who don’t want to switch between prescription

eyeglasses and prescription sunglasses. eyeglasses and prescription sunglasses.

Provide the convenience of having a pair of sunglasses and transparent Provide the convenience of having a pair of sunglasses and transparent

glasses in one pair of lenses. glasses in one pair of lenses.

PC lenses have millions of light absorbing molecules that are PC lenses have millions of light absorbing molecules that are

transparent in artificial light, which is free of UV rays. transparent in artificial light, which is free of UV rays.

When exposed to UV rays from natural sunlight, however, the molecules When exposed to UV rays from natural sunlight, however, the molecules

undergo a chemical process, causing them to absorb light and to darken.undergo a chemical process, causing them to absorb light and to darken.

PC lens darken automatically after approximately 30 seconds of natural PC lens darken automatically after approximately 30 seconds of natural

light and lighten after approximately 5 minutes of artificial light. light and lighten after approximately 5 minutes of artificial light.


Photochromism Photochromism Is a reversible transformation of a chemical species induced in one Is a reversible transformation of a chemical species induced in one

or both directions by absorption of electromagnetic radiation or both directions by absorption of electromagnetic radiation

between two forms, A and B, having diferent absorption spectra. between two forms, A and B, having diferent absorption spectra.

The phenomenon was discovered in the late 1880s, including work The phenomenon was discovered in the late 1880s, including work

by Markwald, who studied the reversible change of color of 2,3,4,4-by Markwald, who studied the reversible change of color of 2,3,4,4-

tetrachloronaphthalen-1(4H)-one in the solid state. tetrachloronaphthalen-1(4H)-one in the solid state.

He labeled this phenomenon "phototropy", and this name was used He labeled this phenomenon "phototropy", and this name was used

until the 1950s when Yehuda Hirshberg, of the Weizmann Institute until the 1950s when Yehuda Hirshberg, of the Weizmann Institute

of Science in Israel, while studying the phenomenon proposed the of Science in Israel, while studying the phenomenon proposed the

term "photochromism", which we use today. term "photochromism", which we use today.


Photochromic materialsPhotochromic materials

Reversible photochromics Reversible photochromics

Irreversible photochromics Irreversible photochromics


Grades Grades


Most common processes involved in Most common processes involved in photochromism are: photochromism are:

Pericyclic reactions, Pericyclic reactions,

Cis-trans isomerizations,Cis-trans isomerizations,

Intramolecular hydrogen transfer, Intramolecular hydrogen transfer,

Intramolecular group transfers, Intramolecular group transfers,

Dissociation processes and Dissociation processes and

Electron transfers (oxidation-reduction).Electron transfers (oxidation-reduction).


Photochromic moleculesPhotochromic molecules May belong to various classes: May belong to various classes:

triarylmethanes, triarylmethanes,

stilbenes, stilbenes,

azastilbenes, azastilbenes,

nitrones,nitrones,

fulgides, fulgides,

spiropyrans, spiropyrans,

naphthopyrans, naphthopyrans,

spiro-oxazines, and others. spiro-oxazines, and others.

For example, the spiro form of an oxazine is a colorless leuco dye; the conjugated system of the oxazine and For example, the spiro form of an oxazine is a colorless leuco dye; the conjugated system of the oxazine and another aromatic part of the molecule is separated by a sp3-hybridized "spiro" carbon. another aromatic part of the molecule is separated by a sp3-hybridized "spiro" carbon.

After irradiation with UV light, the bond between the spiro carbon and the oxazine interrupts, the ring opens, the After irradiation with UV light, the bond between the spiro carbon and the oxazine interrupts, the ring opens, the spiro carbon achieves sp2 hybridization and becomes planar, the aromatic group rotates, aligns its π-orbitals with spiro carbon achieves sp2 hybridization and becomes planar, the aromatic group rotates, aligns its π-orbitals with the rest of the molecule, and a conjugated system forms, with ability to absorb photons of visible radiation, and the rest of the molecule, and a conjugated system forms, with ability to absorb photons of visible radiation, and therefore appear colorful. therefore appear colorful.

When the UV source is removed, the molecules gradually relax to their ground state, the carbon-oxygen bond When the UV source is removed, the molecules gradually relax to their ground state, the carbon-oxygen bond renews, the spiro atom becomes sp3 again, and the molecule returns to its colorless state.renews, the spiro atom becomes sp3 again, and the molecule returns to its colorless state.


Photochromic dyesPhotochromic dyes Photochromic dyes tend to be inherently unstable in their open, colored Photochromic dyes tend to be inherently unstable in their open, colored

form. form.

Their lifetime is therefore significantly negatively affected by exposure Their lifetime is therefore significantly negatively affected by exposure to UV light, as the open form is susceptible to degradation by oxygen to UV light, as the open form is susceptible to degradation by oxygen and free radicals. and free radicals.

Incorporation of the dyes into a polymer matrix, adding a stabilizer, or Incorporation of the dyes into a polymer matrix, adding a stabilizer, or providing a barrier to oxygen and chemicals by other means prolongs providing a barrier to oxygen and chemicals by other means prolongs their lifetime.their lifetime.

Photochromic dyes usually have the appearance of a crystalline powder. Photochromic dyes usually have the appearance of a crystalline powder. In order to achieve the color change, they have to be dissolved in a In order to achieve the color change, they have to be dissolved in a solvent or dispersed in a suitable matrix.solvent or dispersed in a suitable matrix.


Photochromic colorsPhotochromic colors

Usually, four basic colors (magenta, cyan, yellow, Usually, four basic colors (magenta, cyan, yellow,

black) are available commercially.black) are available commercially.

Other colors can be made by combinations.Other colors can be made by combinations.

Spot colors are available from some vendors.Spot colors are available from some vendors.

Exact colors are difficult to achieve, as the exact hue Exact colors are difficult to achieve, as the exact hue

depends on many factors, including the intensity of depends on many factors, including the intensity of

the UV radiation and temperature.the UV radiation and temperature.


Photochromic colors changePhotochromic colors change

Usually between a leuco form in base state to a colored form Usually between a leuco form in base state to a colored form

after exposure to UV radiation. after exposure to UV radiation.

The rate of change varies by color. The rate of change varies by color.

In some formulations, the yellow color takes the longest time In some formulations, the yellow color takes the longest time

to fade back to colorless and requires exposure to visible light to fade back to colorless and requires exposure to visible light

for such transition. for such transition.

Transition between two colors can be achieved by mixing the Transition between two colors can be achieved by mixing the

photochromic dye with an UV-transparent permanent dye.photochromic dye with an UV-transparent permanent dye.


Photochoromatic lenses not darken in… Photochoromatic lenses not darken in…

At indoors (room light does At indoors (room light does

not contain UV) not contain UV)

While driving the car While driving the car

( windshield absorbs some of ( windshield absorbs some of

the UV light.) the UV light.)


Reversible photochromicsReversible photochromics

Work by changing their chemical structure after absorbing Work by changing their chemical structure after absorbing

UV light. UV light.

The UV light causes the photochromics to absorb colour and The UV light causes the photochromics to absorb colour and

then change back to clear when the UV source is removed. then change back to clear when the UV source is removed.

Can cycle thousands of times depending upon the application. Can cycle thousands of times depending upon the application.

Also can change from one color to a different color by Also can change from one color to a different color by

combination with a permanent pigment.combination with a permanent pigment.


Reversible photochromicsReversible photochromics One of the most famous reversible photochromic One of the most famous reversible photochromic

applications in color changing lenses, also found in novelty applications in color changing lenses, also found in novelty

applications such as toys, cosmetics, and industrial applications such as toys, cosmetics, and industrial

applications. applications.

The largest limitation in using PC technology is that the The largest limitation in using PC technology is that the

materials cannot be made stable enough to withstand materials cannot be made stable enough to withstand

thousands of hours of outdoor exposure so long-term thousands of hours of outdoor exposure so long-term

outdoor applications are not appropriate at this time.outdoor applications are not appropriate at this time.


Irreversible photochromicsIrreversible photochromics

A term is used to describe materials that undergo A term is used to describe materials that undergo

permanent color change during exposure to permanent color change during exposure to

ultraviolet radiation. ultraviolet radiation.

Because by definition photochromics are Because by definition photochromics are

reversible, there is no such thing as an reversible, there is no such thing as an

"irreversible photochromic"irreversible photochromic


Silver halideSilver halide A silver halide is one of the compounds formed between silver and one A silver halide is one of the compounds formed between silver and one

of the halogens, usually of the halogens, usually

Silver bromide (AgBr), Silver bromide (AgBr),

Silver Chloride (AgCl) and Silver Chloride (AgCl) and

Silver Iodide (AgI). Silver Iodide (AgI).

As a group, they are often referred to as the silver halides, and are often As a group, they are often referred to as the silver halides, and are often

given the pseudo-chemical notation AgX. given the pseudo-chemical notation AgX.

Although most silver halides involve silver atoms with oxidation states Although most silver halides involve silver atoms with oxidation states

of +1 (Ag+), silver halides in which the silver atoms have oxidation of +1 (Ag+), silver halides in which the silver atoms have oxidation

states of +2 (Ag2+) are known, of which Silver (II) fluoride is the only states of +2 (Ag2+) are known, of which Silver (II) fluoride is the only

known stable one.known stable one.


Silver halideSilver halide Used in photographic film and photographic paper where an Used in photographic film and photographic paper where an

emulsion of silver halide crystals in gelatin is coated on to a emulsion of silver halide crystals in gelatin is coated on to a film base, glass or paper substrate. film base, glass or paper substrate.

The gelatin is a vital part of the emulsion as it contains trace The gelatin is a vital part of the emulsion as it contains trace elements which increase the light sensitivity of the emulsion. elements which increase the light sensitivity of the emulsion.

Silver bromide and silver chloride may be used separately or Silver bromide and silver chloride may be used separately or combined, depending on the sensitivity and tonal qualities combined, depending on the sensitivity and tonal qualities desired in the product. desired in the product.

Silver iodide is always combined with silver bromide or silver Silver iodide is always combined with silver bromide or silver chloride.chloride.


Silver halidesSilver halides Silver halides are also used to make some corrective lenses darken Silver halides are also used to make some corrective lenses darken

when exposed to ultraviolet light.when exposed to ultraviolet light.

When a silver halide crystal is exposed to light, a When a silver halide crystal is exposed to light, a sensitivity specksensitivity speck on on

the surface of the crystal is turned into a small speck of metallic silver the surface of the crystal is turned into a small speck of metallic silver

(these comprise the invisible or (these comprise the invisible or latent imagelatent image). If the speck of silver ). If the speck of silver

contains approximately four or more atoms, corresponding to an contains approximately four or more atoms, corresponding to an

absorption of four or more photons, it is rendered developable - absorption of four or more photons, it is rendered developable -

meaning that it can undergo development which turns the entire meaning that it can undergo development which turns the entire

crystal into metallic silver.crystal into metallic silver.


A sensitivity speckA sensitivity speck

is an imperfection (dislocation) in the crystal lattice of silver halide (usually is an imperfection (dislocation) in the crystal lattice of silver halide (usually silver bromide), where a positively charged cluster of silver ions is exposed to silver bromide), where a positively charged cluster of silver ions is exposed to the crystal surface. When the silver halide grain is exposed to light, the the crystal surface. When the silver halide grain is exposed to light, the photons interact with the halide anions and knock out their electrons. The photons interact with the halide anions and knock out their electrons. The electrons then travel through the lattice, until they are captured by the electrons then travel through the lattice, until they are captured by the dislocation. There they recombine with silver ions, forming neutral silver dislocation. There they recombine with silver ions, forming neutral silver atoms. Tiny clusters of these silver atoms form the latent image.atoms. Tiny clusters of these silver atoms form the latent image.

If such speck of silver contains approximately four or more atoms, If such speck of silver contains approximately four or more atoms, corresponding to an absorption of four or more photons, it is rendered corresponding to an absorption of four or more photons, it is rendered developable - meaning that it can undergo development which turns the entire developable - meaning that it can undergo development which turns the entire crystal into metallic silver.crystal into metallic silver.


Glass Photochromic LensesGlass Photochromic Lenses Photochromic process is different for glass and plastic lenses.Photochromic process is different for glass and plastic lenses.

Glass lensesGlass lenses contain millions of silver halide crystals embedded contain millions of silver halide crystals embedded throughout the lens material. throughout the lens material.

When exposed to sunlight, UV rays transform the crystals into light-When exposed to sunlight, UV rays transform the crystals into light-absorbing particles. absorbing particles.

As these particles absorb light, the lens darkens and the amount of light As these particles absorb light, the lens darkens and the amount of light passing through the lens is reduced.passing through the lens is reduced.

When the lenses are removed from sunlight and the stimulating UV When the lenses are removed from sunlight and the stimulating UV radiation is no longer present, the crystals return to their original radiation is no longer present, the crystals return to their original orientation and the lenses become clear.orientation and the lenses become clear.


Plastic Photochromic LensesPlastic Photochromic Lenses Owes its darkening to the presence of spiro-indoline organic Owes its darkening to the presence of spiro-indoline organic

molecules instead of silver halide crystals. molecules instead of silver halide crystals.

When activated by UV rays ,the spiro-indoline molecules When activated by UV rays ,the spiro-indoline molecules scatter, absorbing sunlight and reducing the amount of visible scatter, absorbing sunlight and reducing the amount of visible light that penetrates the lens. light that penetrates the lens.

when the lens is removed from sunlight the chemical reaction when the lens is removed from sunlight the chemical reaction reserves and the lens returns to its clear state.reserves and the lens returns to its clear state.

Not recommendable to use more than 2 years because it Not recommendable to use more than 2 years because it gradually loses its darkening ability with time.gradually loses its darkening ability with time.

Most popular plastic pc lenses, made by Most popular plastic pc lenses, made by Transitions*Transitions* Optical. Optical.


Plastic photochromic lensesLinksIt was only very recently that manufacturers Plastic photochromic lensesLinksIt was only very recently that manufacturers succeeded in producing plastic lenses with photochromic properties succeeded in producing plastic lenses with photochromic properties comparable to those of glass lenses.comparable to those of glass lenses.

Organic photochromic lenses are produced from a special plastic which is Organic photochromic lenses are produced from a special plastic which is optimized for the absorption of photochromic dyes. Unlike glass photochromic optimized for the absorption of photochromic dyes. Unlike glass photochromic lenses, they are not given their photochromic properties until the semi-finished lenses, they are not given their photochromic properties until the semi-finished or finished stage. In this process – known as photochromization – millions of or finished stage. In this process – known as photochromization – millions of photochromic molecules are incorporated in the front surface of the lens at a photochromic molecules are incorporated in the front surface of the lens at a depth of approx. 0.15 mm.depth of approx. 0.15 mm.


The Photochromic moleculesThe Photochromic molecules Are primarily indolino-spironaphthoxacins. Are primarily indolino-spironaphthoxacins.

These change their chemical structure when they are irradiated with UV These change their chemical structure when they are irradiated with UV and short-wave blue light. and short-wave blue light.

Much like a flower when exposed to sunlight, they unfold and cause the Much like a flower when exposed to sunlight, they unfold and cause the lens to change colour.lens to change colour.

If the energy level of the UV radiation decreases or – as is the case when If the energy level of the UV radiation decreases or – as is the case when the wearer goes indoors – no UV is present at all, the molecules close again. the wearer goes indoors – no UV is present at all, the molecules close again. The lens clears and adopts an attractive filter tint.The lens clears and adopts an attractive filter tint.

As the molecules are only found on the lens surface, the darkening process As the molecules are only found on the lens surface, the darkening process takes place evenly over the entire surface, irrespective of the dioptric takes place evenly over the entire surface, irrespective of the dioptric power.power.


Plastic photochromic process Plastic photochromic process

"in-mass" technology."in-mass" technology. Light-sensitive molecules Light-sensitive molecules

distributed throughout the distributed throughout the

lens material lens material

(just as silver halide crystals are (just as silver halide crystals are

in glass photochromatic lenses). in glass photochromatic lenses).

"imbibing" technology."imbibing" technology. Instead of distributing light-Instead of distributing light-

sensitive particles, Transitions sensitive particles, Transitions

applies a thin layer of applies a thin layer of

photochromic material to the front photochromic material to the front

surface of its lenses. surface of its lenses.

This material penetrates the lens This material penetrates the lens

surface evenly to a depth of surface evenly to a depth of

approximately 0.15 mm. approximately 0.15 mm.


"Break-In" Period"Break-In" Period It takes several exposures to sunlight before a new pair of photochromic It takes several exposures to sunlight before a new pair of photochromic

lenses will darken and lighten as designed. lenses will darken and lighten as designed.

Allow your lenses to be exposed to sunlight at least five periods of 30 Allow your lenses to be exposed to sunlight at least five periods of 30 minutes or longer to "break-in" the photochromic process.minutes or longer to "break-in" the photochromic process.

The Effect of TemperatureThe Effect of Temperature

All photochromic lenses perform better (i.e. get darker and change All photochromic lenses perform better (i.e. get darker and change faster) in cold weather. faster) in cold weather.

For standardization purposes, photochromic lenses are usually tested at For standardization purposes, photochromic lenses are usually tested at an ambient temperature of approximately 72 degrees Fahrenheit. an ambient temperature of approximately 72 degrees Fahrenheit.

At higher temperatures, photochromic lenses may take more time to At higher temperatures, photochromic lenses may take more time to change and may not darken to the same degree. change and may not darken to the same degree.


Photochromic Lenses and DrivingPhotochromic Lenses and Driving Photochromic lenses require exposure to UV radiation from the Photochromic lenses require exposure to UV radiation from the

sun to darken. sun to darken.

Since automobile windshields block some UV rays, PC lenses do Since automobile windshields block some UV rays, PC lenses do

not darken appreciably inside many cars. not darken appreciably inside many cars.

For the best vision and comfort while driving in bright sunlight, For the best vision and comfort while driving in bright sunlight,

Consider a pair of clip-on sunglasses to wear over photochromic Consider a pair of clip-on sunglasses to wear over photochromic

lenses or a separate pair of polarized sunglasses.lenses or a separate pair of polarized sunglasses.


Reducing Glare from ReflectionsReducing Glare from Reflections To eliminate glare from light reflecting off the back surface of To eliminate glare from light reflecting off the back surface of

photochromic lenses, A-R coating can be applied.photochromic lenses, A-R coating can be applied.

AR coating AR coating

does not adversely affect the photochromic process. does not adversely affect the photochromic process.

to any PC lens will increase the light transmittance in both the to any PC lens will increase the light transmittance in both the

indoor (clear) and outdoor (dark) states. indoor (clear) and outdoor (dark) states.

Exact percentages will vary depending on the brand of AR coating. Exact percentages will vary depending on the brand of AR coating.

When applied to both surfaces, AR coating can also prolong the effective When applied to both surfaces, AR coating can also prolong the effective

lifetime of some photochromatic lenses.lifetime of some photochromatic lenses.


How long do they last?How long do they last?

Most plastic photochromic lenses Most plastic photochromic lenses

gradually lose some of their ability to gradually lose some of their ability to

change in sunlight after 18 to 24 change in sunlight after 18 to 24

months of use. months of use.

For the best performance, plastic For the best performance, plastic

photochromic lenses should be photochromic lenses should be

replaced every two years.replaced every two years.


Photochromics in power lenses…Photochromics in power lenses…

The whole lens changes when exposed to sunlight. The whole lens changes when exposed to sunlight.

In power lens, the thickest part of the lens will be darker than In power lens, the thickest part of the lens will be darker than the thinner parts. the thinner parts.

If there is a large difference in prescription between the two If there is a large difference in prescription between the two eyes, the stronger power lens will be darker than the weaker eyes, the stronger power lens will be darker than the weaker one.one.

Corning Corning Thin & DarkThin & Dark photochromic glass lenses, which are up photochromic glass lenses, which are up to 30 % lighter in weight than traditional glass lenses and also to 30 % lighter in weight than traditional glass lenses and also thinnerthinner


SunSensors* -lens Corning has recently introduced a lightweight, high index Corning has recently introduced a lightweight, high index

plastic PC lens called SunSensors(R). plastic PC lens called SunSensors(R).

It has photochromic material uniformly distributed into the It has photochromic material uniformly distributed into the

front surface of the lens, but has a penetration depth that is front surface of the lens, but has a penetration depth that is

significantly thicker than the photochromic layer in significantly thicker than the photochromic layer in

Transitions lenses. Transitions lenses.

This extra-thick photochromatic layer enables SunSensors This extra-thick photochromatic layer enables SunSensors

lenses to change faster and get darker than other lenses to change faster and get darker than other

photochromic lenses, according to the companyphotochromic lenses, according to the company


Rodenstock*-lensRodenstock*-lens ColorMatic ExtraColorMatic Extra from Rodenstock is another mid-index plastic photochromic line. from Rodenstock is another mid-index plastic photochromic line.

A photochromic dye is mixed throughout these gray lenses. A photochromic dye is mixed throughout these gray lenses.

ColorMatic Extra lenses can be tinted to alter the color or darken the lenses.ColorMatic Extra lenses can be tinted to alter the color or darken the lenses.

In addition, Hoya Lens makes In addition, Hoya Lens makes SungraySungray Lenses, mid-index plastic photochromics with Lenses, mid-index plastic photochromics with

UV-activated color-changing molecules blended throughout the lens material. UV-activated color-changing molecules blended throughout the lens material.

They can also be tinted.They can also be tinted.TransitionsTransitions lenses are available for nearly every lens design, lenses are available for nearly every lens design,

refractive index and prescription. refractive index and prescription.

Performance features include advanced variable-tint technology that allows rapid Performance features include advanced variable-tint technology that allows rapid

darkening when you go outside (and rapid return to clear when you go in), and 100% darkening when you go outside (and rapid return to clear when you go in), and 100%

UV protection. UV protection.


Vision enhancement with PC lensesVision enhancement with PC lenses Beyond the convenience of having lenses that can be worn both indoors and outdoors, Beyond the convenience of having lenses that can be worn both indoors and outdoors,

some photochromic lenses also have medical applications. some photochromic lenses also have medical applications.

Corning's CPF family consists of glass photosensitive lenses with colors in the red Corning's CPF family consists of glass photosensitive lenses with colors in the red family. family.

They are used to enhance the vision of patients who have various ocular pathologies. They are used to enhance the vision of patients who have various ocular pathologies.

Low vision Practitioners are familiar with these lenses and can help patients determine Low vision Practitioners are familiar with these lenses and can help patients determine which color will be the most helpful. which color will be the most helpful.

Another glass photochromic lens that is designed for use by individuals who have Another glass photochromic lens that is designed for use by individuals who have beginning-to-moderate light sensitivity because of various ocular conditions is Corning's beginning-to-moderate light sensitivity because of various ocular conditions is Corning's GlareCutter. GlareCutter.

This is a darker, more cosmetically pleasing brownish-red that allows a precise level of This is a darker, more cosmetically pleasing brownish-red that allows a precise level of blue light to "leak" through the lens, thus preserving a more natural color scene for the blue light to "leak" through the lens, thus preserving a more natural color scene for the wearer than the more reddish CPF lenses. Lenseswearer than the more reddish CPF lenses. Lenses with Tints with Tints


Brand names…Brand names…

Though photochromic is the proper generic term for all Though photochromic is the proper generic term for all

lenses that darken in sunlight, these lenses are often lenses that darken in sunlight, these lenses are often

referred to by a specific brand name, such as Transitions(R) referred to by a specific brand name, such as Transitions(R)

(made by Transitions Optical) or PhotoGray(R) (made by (made by Transitions Optical) or PhotoGray(R) (made by

Corning). Corning).

Other terms used to describe photochromic lenses include Other terms used to describe photochromic lenses include

variable tint lenses and lenses with sun-activated tints.variable tint lenses and lenses with sun-activated tints.


Thank YouThank You

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Photochromatic lenses