Absorptive Lenses

Question 1

ultraviolet range in nm

Answer 1

295nm - 400nm

Question 2

visible light in nm

Answer 2

400nm- 800nm

Question 3

infrared light in nm

Answer 3

800nm- 1200nm

Question 4

UV-C range in nm

Answer 4

100-280 nm

Question 5

UV-B range in nm

Answer 5

280-315 nm

Question 6

UV-A range in nm

Answer 6

315-400 nm

Question 7

cornea absorbs what % of

• incident UVC
• incident UVB
• incident UVA

Answer 7

• UVC: 100%
• UVB: 90%
• 60% incident UVA

Question 8

the majority of the remaining ____ is absorbed by the lens

Answer 8

UVA

Question 9

does UVA reach the retina?

Answer 9

small portion of UVA reaches the retina

Question 10

how much of the high energy visible light (HEV) passes through the cornea and lens?

Answer 10

85-90%

Question 11

effects of UV absorption of the cornea

Answer 11

• photokeratitis

- pterygia

Question 12

cataracts from UV-A and UV-B light exposure

Answer 12

cortical cataracts: small, 10% increased risk with higher lifetime sunlight exposure, mechanism not fully understood

Question 13

cataracts from infrared light exposure

Answer 13

glass blowers cataract

Question 14

cataracts from high energy microwave

Answer 14

cataracts formed by direct damage to lens fiber cell membranes

Question 15

retinal light damage is from

Answer 15

UV and HEV (photo thermal, photomechanical, photochemical)

Question 16

what type of light is related to macular degeneration?

Answer 16

high energy visible light

Question 17

how can high energy visible light causes macular degeneration?

Answer 17

• short wavelength and blue light cause significant oxidative stress to the RPE
• need further studies and clinical trials to understand fully

Question 18

3 things infrared radiation

Answer 18

• absorption of high energy IR radiation causes vibrational changes in molecules
• increased temperature on tissue causes denaturation of proteins
• results in loss of function of proteins and enzymes critical to metabolic processes

Question 19

effects of infrared radiation on cornea, iris, lens, retina

Answer 19

• cornea: corneal burns
• iris: de-pigmentation & atrophy
• lens: glass blower’s cataract
• retina: burns

Question 20

total light transmission through a lens=

Answer 20

incident light (I) - (reflection + absorption)

Question 21

medications causing increase sensitivity

Answer 21

• tetracycline
• sulfa drugs
• birth control
• diuretics
• tranquilizers

Question 22

protection from UV can be from:

Answer 22

absorptive- metal oxide

or reflective- reflective coating

Question 23

discomfort glare causes:

Answer 23

discomfort but does not affect visual performance

Question 24

disability glare (Veiling glare)

Answer 24

decrease in contrast causing decrease visibility or resolution such as cataracts, UV absorption by the lens, and cornea scarring

Question 25

dazzling glare can cause

Answer 25

photophobia

Question 26

how do glare control lenses work?

Answer 26

block short wavelengths to increase contrast

Question 27

disadvantages of glare control lenses?

Answer 27

may have an effect on color vision, depending on amount of visible spectrum that is absorbed by the lens

Question 28

glass photochromic lens contain

Answer 28

silver halide, breaks into silver and halogen when activated by UV, rebinds to silver after exposure to UV stopped

Question 29

plastic photochromic lenses contain

Answer 29

indolino spiroazines (ISN), this material penetrates the lens surface at about 150 microns, when activated ISN changes structure and darkens- reduces transmittance

Question 30

what does AR coating reduce and increase?

Answer 30

reduces reflection | increases light transmission through the lens

Question 31

the ___ the index, the more light is reflected off the surfaces and therefore the less light transmitted

Answer 31

higher

Question 32

labert's law of absorption

Answer 32

same % of light is absorbed regardless of intensity of incident light through homogenous substance

Question 33

the intensity of transmitted light varies exponentially as a function of

Answer 33

the length of the light path in the absorbing media