TINTS/RADIATION/FILTERS Flashcards
1
Q
When is radiation damaging
A
When absorbed by the cells of the adnexa
2
Q
Cornea absorbs
A
270nm - 3000nm
3
Q
Aqueous absorbs
A
290 - 2700nm
4
Q
Crystalline lens (old) absorbs
A
375 - 2500nm
5
Q
Crystalline lens (young) absorbs
A
310 - 2500nm
6
Q
Vitreous absorbs
A
290 - 1600nm
7
Q
Transmittance
A
Light which passes through a medium, after losses by reflection and absorption, represents the Transmittance of the media
8
Q
Spectral Transmittance
A
Fraction of luminous flux transmitted by a lens as a proportion of incident light, for a specific wavelength
9
Q
Spectral Transmittance details
A
- tells us what a lens transmits for every wavelength
- expressed as %
- transmission curve produced by spectral transmission across a range of wavelengths
10
Q
Luminous transmission (LTF)
A
Measures the transmission of a lens over the visual spectrum
11
Q
LTF details
A
- considers standard light sources
- illuminant D65
- figure to compare tints
- BS states tints should be stated as LTF
12
Q
LTF Formula
A
LTF = luminous flux reaching eye through lens / luminous flux reaching eye without lens
13
Q
UVB
A
- 280-315nm
- most dangerous to ocular tissue
- suburn / BCC
- keratitis / snow blindness
14
Q
UVA
A
- 315-380nm
- long term exposure absorbed by crystalline lens
- DNA damage/ wrinkles/ cataract
15
Q
UV exposure
A
- welding
- physiotherapy
- snow/ sea/ sand reflects high amounts
- delayed symptoms (up to 12 hours)
- itching/ blisters/ lacrimation/ photophobia
