Photochromic Lenses

photochromic lenses

lenses that change in transmission when exposed to light, can perform like sunglasses in darkened state but cannot replace sunglasses behind a car windshield

chemical tempering

disregarding impact resistance & taking only transmission characteristics into consideration, which method is best for hardening a photochromic lens?

F

T/F: imbibition has been the standard technology for the manufacture of glass lenses

1

it is not advisable to replace 1 photochromic lens even if the other lens is less than _____ year old b/c the 2 lenses will age differently

98

glass photochromics absorb ______% UVA radiation

1

AR coated photochromic lenses will have little more than a ____% decrease in darkening compared to photochromic lenses w/o AR coating

silver halide

what type of crystals are added to glass to make photochromic lenses?

molecule rotates w/ UV light & lens darkens

how does a plastic photochromic lens work?

imbibition

transitions are made using an _______ process

red light or infrared radiation (IR)

what 2 optical things can bleach a photochromic lens?

cold, bright

photochromic lenses perform best on ____________ days

optical, thermal

2 types of bleaching for photochromic lenses

speeds up

heat __________ the bleaching process of photochromic lenses

glass

_____ (glass/plastic) photochromic lenses have exposure memory

glass

______ (glass/plastic) photochromic lens transmission is influenced by lens thickness

slows

reaction time of photochromic lenses _____ (speeds/slows) if the lens is heat tempered

darker

a heat tempered photochromic lens is ________ (darker/lighter) in both lightened & darkened states

higher

with an AR coating, standard plastic photochromics transmit a _______ percentage of light than uncoated clear lenses indoors

A & B

standard plastic photochromic lenses absorb ~99.5-100% of what types of UV?

Gen S

• new line of transitions from Essilor

• lenses are clear indoors

• lenses are darker outdoors

• darkens in 25sec

• returns to clear indoors in less than 2min

• available in 8 colors

extremely light sensitive pt

photochromic lenses that darken more are intended for who?

no

are photochromic lenses that darken more completely clear indoors?

UV & visible light

photochromic lenses that darken more are activated by _____________

increases

photochromic lenses w/ polarization have polarization that starts low & _________ as lens darkens

Younger Optics Transitions Driveware

• conventional polarization & tinted photochromic material activated by UV & visible light

• in low daylight, appear yellow/green

• in the car, appear copper

• outside, further activated by UV & appears dark reddish-brown

gray, brown

what are the most common colors of photochromics?

F

T/F: UV or color dyeing a plastic photochromic lens makes the photochromic aspects of the lens work better

reharden the old lens w/ the new

what is the most effective method to use when attempting to match a new glass photochromic replacement lens w/ an older glass photochromic lens?