Transmission & Tints

1. tint of the lens

2. lens transmission

what are the 2 variables for the classification of absorptive lenses?

F

T/F: the longer the wavelength of the UV rays, the greater the likelihood of biologic damage

cornea, vitreous, lens, aqueous

what 4 structures absorb much of the UV & IR light that reaches the eye before it gets to the retina?

T

T/F: the transmission curve for pink matches clear

F

T/F: absorption used to be denoted by a letter or number, the higher the number or further down the alphabet, the lighter the tint will be

100-transmission

% absorption =

glare control

________ lenses block out short wavelength light (primarily blue)

faceform, short

the best UV protecting options for eyeglass frames are a ________ & ______ vertex distance

yellow

_________ tinted lens have been shown to increase contrast of some objects against the blue sky

green

which tinted lens has a transmission curve that is most similar to color sensitivity curve for the human eye

gray

_____ tint is satisfactory & used by those w/ color vision deficiencies

T

T/F: a lifeguard is exposed to bright sunlight every day for long periods of time, his or her dark adaptation does not return to what it used to be even after a full night’s darkness

20/46

the VA of an individual who normally sees 20/20 but is driving at night w/ a tinted windshield may have reduced VA to ______

F

T/F: all high-index plastics can be dyed

15

it should be noted that people who are exposed to sunlight for long periods of time on a continual basis will require sun lenses that transmit ______% or less

darker, lightening

high plus pretinted glass lenses will have a _________ central portion w/ the tint _________ rapidly towards the periphery

high

Welder’s burn is an example of ________ level UV radiation that causes ocular damage

cumulative

formulation of cataracts is an example of ________ UV radiation that causes ocular damage

UVA

relatively speaking, least harmful of the radiation bands

UVB

if present in sufficient quantity, long enough duration, or both, will cause sunburn, photokeratitis, cataracts, & retinal lesions

UVC

high in energy, but filtered out by Earth’s ozone layer

UV vacuum

is present outside the Earth’s atmosphere, but is filtered by the atmosphere

pinguecula

__________ manifests itself as a yellowish thickening of the conjunctiva, usually on the nasal side of the cornea

T

T/F: people who live where UV radiation is high, such as at high altitudes or tropical areas, develop cataracts earlier in life

A

what type of UV is 400-320nm?

B

what type of UV is 320-290nm?

C

what type of UV is 290-200nm?

1. beginning cataracts

2. macular degeneration

3. pterygia

4. pinguecula

5. aphakia

6. pseudophakia

what are some examples of people who need greater UV protection?

1. sulfonamides

2. tetracyclines

3. diuretics

4. tranquilizers

5. drugs for hypoglycemia

6. OCPs

what are some examples of drugs that increase an individual’s need for UV protection?

1. outdoors b/t 10am-2pm in summer

2. long hours outdoors

3. skiing

4. sun bathing

5. high-altitude conditions

6. live near the equator

what sort of environmental conditions increase the need for greater UV protection?

1. welders

2. dentists (those who work near UV lamps)

3. workers in industry that use UV radiation

what are some examples of occupations that need greater UV protection?

1. lenses w/ UV filter directly in the material

2. photochromic lenses

3. lenses w/ the UV filter in the coating

4. lenses w/ a dyed-in UV filter

5. polarizing lenses

6. glare-control lenses

what are some examples of different types of lenses that block UV radiation?

15-30%

what is the normal transmission through absorptive lenses?

8%

general purpose absorptive lenses should not be less than _____ transmission for effective UV protection.

10, hours

exposure to bright sunlight for more than 2-3hrs causes dark adaptation to become effective _____ min later & take several _________ longer to reach maximum

10-15%

what percent transmission sunglasses are required to prevent changes in dark adaptation with prolonged sun exposure?

20/20

what is the daytime VA?

20/32

what is the nighttime VA?

20/40

what is the nighttime VA through an 82% transmitting pink tint?

20/46

what is the nighttime VA through a tinted windshield?

20/60

what is the nighttime VA through a tinted windshield & an 82% transmitting pink tint?

clear, pink, yellow, brown, green, gray

list the types of lens colors

pink

• tint color with uniform transmission across the visible spectrum

• do not cause color distortions

• generally used for unfavorable indoor lighting situations

yellow

• tint color with a higher absorption of shorter visible wavelengths

• visual performance through this tint is approximately the same as vision through a spectrally neutral filter w/ the same absorption

• can increase contrast in some instances

• traditionally used in competitive shooting

brown

• tint color with a higher absorption of shorter visible wavelengths

• most often used for sun lenses in Germany & other middle-European countries

• similar characteristics to yellow lenses

• can improve contrast

green

• tint color with a transmission curve that closely approximates the color sensitivity curve for the human eye

• obtains its color from ferrous oxide

• glass lenses tinted in this color have good absorption in IR & UV spectrum

• lenses vacuum coated in this color have acceptable IR absorption

• a plastic lens dyed this color has poor IR absorption

gray

• tint color most popular for sun protection

• even transmission through the whole visible spectrum

• allows colors to be seen in their natural state relative to each other

• good for use by those w/ color deficiencies (doesn’t help in perception but doesn’t cause further issues)

1. reduce intensity of sunlight

2. eliminate parts of the optical spectrum that are not required for vision or are hazardous to eyes

3. provide enough protection while being worn during the day so that the wearer’s dark adaptation & night vision are preserved

4. maintain normal color vision & allow wearer to distinguish traffic signals

5. resist impact & scratching & require minimum care

describe qualities of an ideal pair of sunglasses?

CR39

lens material that is easy to dye & very versatile

polycarbonate

lens material that is difficult to dye due to its anti-scratch coating

high index

lens material that dyes more slowly than CR39 & may require more special processing

trivex

lens material that dyes more rapidly & successfully than other non-CR39 plastic materials

upper, lower

gradient lenses have a darker _______ portion that gradually lightens toward the _______ part of the lens

anytime

when can clear CR39 lenses be tinted?

anytime as long as they are not AR coated

when can plastic lenses that have been tinted be bleached & re-tinted?

gray, brown

what 2 lens colors are most often used for sun lenses in Germany & middle-European countries?

T

T/F: the longer a plastic lens is left in dye, the darker the tint will be

F

T/F: single, high level amounts of UV radiation can be damaging, but the eye is able to recover from long-term, low-level amounts of UV exposure w/o being affected

F

T/F: a person’s ability to work effectively under a situation of reduced illumination increases w/ age

T

T/F: although in certain instances acuity may increase when a 10% NDF is worn in bright sunlight, persons older than age 40 experience poorer vision if the filter is darker than 10%

F

T/F: exposure to sunlight over an extended period of time will reduce the time needed for the eye to dark adapt

F

T/F: yellow tints help nighttime driving because they eliminate blue haze

all will be equally dark

which of the following lenses will be the darkest if all are to be vacuum coated to the equivalent gray #3 tint?

+7.00D, plano, -7.00D

UVA

which UV radiation has the longest wavelength?

thickness

the tint of tinted glass lenses varies with _______

poor

dyed plastic lenses have _______ IR absorption