Polaroid lenses

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POLAROID LENSES

MADE BY : SWATI PANARAFROM : BHARTIMAIYA COLLEGE OF

OPTOMETRY2nd YEAR 3rd SEMESTER

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INTRODUCTION

• Polarized lenses are transparent pieces of material, usually glass or plastic, that

block certain types of light waves.

• Polaroid polarized lenses block out virtually 100% of glare.

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OTHER NAME

• ANTI GLARE LENSES

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• Light reflected from surfaces like a flat road or smooth water is generally horizontally polarized.

• This horizontally polarized light is blocked by the vertically oriented polarizer in the lenses. The result: a reduction in annoying and sometimes dangerous glare.

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• WHEN DIRECT SUNLIGHT OR ARTIFICIAL LOGHT HIT A SMOOTH SURFACE AT A GIVEN ANGLE , IT REFLECT OFF THE SMOOTH SURFACE AND TRAVELS IN THE SAME DIRECTION , INTENSIFYING THEIR EFFECT ON THE EYES.

• THIS PHENOMENON PRODUCE GLARE.

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GLARE-• TWO TYPES- DISCOMFORT GLARE DISABLILTY GLARE

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DISABILITY GLARE-• The most dangerous form of glare is disability

glare. This is the type of glare that causes the patient to instinctively avert his or her eyes.

• Reflection off the roads, water, ice, hoods of vehicles and sand are the main causes of this glare type.

• Further, it is disability glare that most concerns the eye care professional when providing the patient with the appropriate sunwear.

• Disability glare poses a hazard to the patient if not treated properly, due to safety risks that averting the eye can cause during activities such as driving and water sports .

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DISCOMFORT GLARE-• Discomfort glare is a very subtle form of

glare. • It causes the visual system to over exert

itself resulting in eye strain, headaches, and physical fatigue.

• Common causes of this glare type are light that is reflected off spectacle lenses, computer screens, windshields; as well as light color surfaces such as paper and walls. 

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Brewster’s Angle

• This occurs when the tangent of the angle of incidence is equal to the index of refraction of the medium to which the light is incident , that is Tan i = n

• The plane of polarization of the reflected light is parallel to the reflecting surface or perpendicular to the plane of the incident light.

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Manufacturing• Polarizing filters are created by stretching sheets

of polyvinyl alcohol (PVA) so its molecules align in long directional chains. The PVA is then passed through an iodine solution where the light absorbing iodine molecules attach to the molecular chains forming the microscopic blinds. The film is then incorporated into the lens blank as it is poured, creating polarized lenses

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Manufacturing

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Manufacturing

• The thin polarizing sheet is then laminated between two layers of coated cellulose acetate butyrate and is pressed to the desire curvature

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POLARIZATION• Polarization is the breaking down of a light wave

that travels in all directions, into rays that travel in two directions.

• Although the direct light coming from the sun in not polarized, when the light hits a highly reflective surface, it is broken down into horizontal and vertical polarized beams.

• Since most reflective surfaces are on a horizontal plane, such as water or the hood of a car, the polarized beams that cause the most disability glare is the horizontal polarized light.

• Therefore, to eliminate the horizontal polarized light from reaching the eye, a filter is fixed at an angle that only allows vertical polarized light to enter the eye .

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• Principle of polarized lens is best illustrated by observing Venetian blind which blocks light at certain angles, while allows light to transmit through it at certain

other angle.

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Recommendation of Polaroid lenses

• Day time drivers• Fisherman• At beach/sea shores• Snowfield workers, skiers• Good for UV protection• People working on sand

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AVAIBELITY

• SINGLE VISION LENSES• MULTIFOCAL• THEY ARE AVAILABLE IN GLASS PLASTIC ,

POLY CARBONATE , HI INDEX.• NOW , POLAROID LENSES ARE AVAILABLE IN

PHOTO CHROMIC LENS.• TINT LENS IS AVAOLABLE.

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ADVANTAGES• Filters glare • Enhances contrast • Constant density tints • Backside AR compatibility • Tint able and coat able • Light weight • Thin

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• Depth perception• Eyes feel rested• Reduce reflection• Realistic perception• Improve visual acuity , provide safety• Comfortable Attractive-looking sun wear• Reduces eye strain , greater comfort

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Vision without Polaroid lenses

Vision with Polaroid lenses

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COLOUR

• Gray: The most popular color for sunglasses in the U.S., gray transmits all colors evenly. It makes a good everyday or all-purpose choice of sunglasses. It is recommended for ocean fishing, where the water tends to be blue. "Classic gray" is a color that provides near-natural vision and true color perception

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• All purpose sun wear• Driving• Sport activities• Water activities

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• Brown: Because brown improves contrast and depth perception, it is best for driving and shallow-water fishing. Light brown is a good color for overcast days and is recommended for skiers and golfers. Brown is another popular color, especially among the fashion-conscious, because many fashion authorities believe that brown is flattering to the face.

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• All purpose sun wear• Driving • Sport activities• Water activities filters blue light , improving

visual acuity• Sharp definition for golf

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• Blue: Blue allows the most blue light to filter through, so it is good in partly cloudy weather. Blue is a popular lens color among tennis players and golfers.

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• Green: Green improves contrast slightly, and keeps a good balance among the colors of light. It is a popular color for tennis, golf, or driving

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• Yellow: This color filters out blue light. Because it provides the highest level of contrast, it is perfect for cloudy-day driving.

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• Violet: Violet causes green to fade and enhances orange, green, and black. It is good for shooting under average conditions.

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• Red: Red is primarily used by sportsmen working in bright, sunny places.

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• Copper: Copper provides maximum contrast and is best for any activity in which good vision is important .

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USES

• Reducing glare can ease the eye strain drivers feel from long hours on the road.

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• Fishermen can often see under the surface of water using the lenses, which helps them to see fish or other objects.

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• Photographers use polarizing filters on camera lenses to enrich the images they capture by giving them more contrast, and to increase the range of effects they can produce.

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• Using horizontally and vertically polarized lenses together makes one type of three-dimensional (3-D) movies possible. Two images are projected onto a 3-D movie screen: one is polarized vertically and one horizontally.

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Disadvantage

• It includes additional cost and time limited tint color choices , and fact that many patients and dispensers misunderstand the uses of polarized lenses.

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LIMITATIONS.• Polarized glasses do not provide universal

protection from glare.• If the wearer tilts his or her head past 45° or so,

more of the horizontal light can enter and cause bright spots.

• In addition, these lenses do not usually work with snow glare because snow tends to reflect light equally in all directions, rather than the mostly horizontal reflection off of liquid water.

• It is strongly recommended that downhill skiers in particular not wear polarized sunglasses; ice does reflect horizontally, and these glasses can make dangerous icy spots less visible.

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• Because the polarizing stripes reduce the amount of light entering the eye, these lenses should not be used at night or in other situations where clear lenses are required.

• It is not possible to make such lenses truly clear; even those with low levels of polarization have a slightly gray hue. Some people find that looking through the lenses for too long a period of time can cause headaches and eye strain.

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• Polarized lenses can cause distortions in the way wearers see liquid crystal displays (LCDs), rendering some cell phone screens, clocks, and other displays unreadable.

• The texture of laminated or heat-treated glass, like a windshield, can be made more prominent by looking at it through a polarized lens, making the glass difficult to see through. Pilots should not use polarized glasses because they can make flight instruments difficult to read and other objects in the sky — including other airplanes — less visible.

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DISPENSING TIPS

• PLEASE,DO NOT TEMPER POLARIZED GLASS !• Remember, polarized glass is already

tempered. Attempting to do so again will crack your lenses.

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       Violet 32% 55%

Increases contrast and dampens certain backgrounds. Violet is often used by shooters in average or bright conditions. Also used for skiing, snowmobiling and golfing.

       Blue 20% 60%

Is used in partly cloudy to sunny conditions. Good for tennis, golf, and shooting at green targets. Blue lenses let in the maximum amount of blue light

- Color

Polarizing

Efficiency

Trans-missio

nUse

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- Color

Polarizing

Efficiency

Trans-missio

nUse

       Orange 70% 50%

Increases contrast and blocks blue light. Best in overcast or partly cloudy conditions. This is the most common lens color used for clay target shooting. Also used for hunting, biking and skiing.

       Green 50% 60%

Has slightly better contrast than the gray colors, but is not considered a high contrast lens. Green maintains true color balance and is a good choice for varying light conditions. Used for tennis driving and golf, as well as an all-purpose color

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Brown C 93% 25%

Provides excellent contrast and improves visual acuity and depth perception. Good for bright sunny and varying conditions. Reduces blue light. Best for driving, golfing and shallow water fishing.

Brown A 92% 45%

A lighter shade of the Brown C color. Improves contrast and depth perception. Good for partly sunny to bright sunny days. Can be used as a base for creating custom colors

Color

Polarizing

Efficiency

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- Color

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      Gray C 98% 25%

Reduces the maximum amount of visible light and allows for true color recognition. Good for bright sunny days and heavy glare situations. Best uses include driving, deep-water fishing and general use.

      Gray A 98% 55%

A lighter shade of the Gray C lens, transmits colors evenly and allows for true color recognition. Good for partly sunny to bright sunny days. Can be used as a base creating custom colors.

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- Color

Polarizing

Efficiency

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       Melanin 85% 25%

Blocks high amounts of blue light, while maintaining true color balance. Melanin provides high contrast for better visual acuity and is good for bright sunny and varying conditions. Great for golfing, driving and fishing, or anyone with macular degeneration.

       Red 75% 55%

A vibrant color that increases contrast. Often used for fishing in early morning or late evening hours. Used in target shooting for bright sunny conditions. Also used for skiing and hunting

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       Yellow 10% 80%

Provides the maximum light transmission of any polarized lens. Increases contrast and filters out some blue light. Used in low light conditions such as overcast or cloudy days. Popular among shooters, hunters.*

- Color

Polarizing

Efficiency

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POWER RANGE• Sphere : + 6.00 to – 8.00 D in 0.25 D steps• Cylinder : + 3.00 to – 3.00 D in 0.25 D

steps• Add power : In form of single vision lenses

+0.75 to + 3.00D in 0.25 D steps

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•THANK YOU