DIS - Eye Trauma IV: Radiation - Week 8 Flashcards
True or false
Artificial sources tend to emit radiation in excess of the suns radiation.
True
What two gases are responsible for absorbing most of the UV radiation from the sun? List three other important componrnts and what they absorb.
Oxygen gas and ozone
H2O, CO2, and dust help absorb some infrared
In terms of damage to tissue, what does the effect of EM radiation depend on (2)?
Wavelength and photon energy
What are the two distinct damage mechanisms of EM radiation? Note the wavelengths that generally cause each.
Thermal
-long wavelengths, low photon energy
-causes molecular agitation
Photochemical
-short wavelengths, high photon energy
-causes excitation, breaking chemical bonds
At what energy levels does ionisation begin to occur?
> 6eV
Note what wavelengths the following structures absorb (at ~90% transmittance):
Cornea
Aqueous
Lens
Vitreous
Cornea ~350nm
Aqueous ~400nm
Lens ~450nm
Vitreous ~500nm
What ocular structures absorb UVB and UVC (1)?
The cornea
What ocular structures absorb UVA (2)?
The lens and iris
What ocular structures absorb IRC (1)?
The cornea
What is the range of UV light? Note the range for each subcategory.
200nm to 400nm
UVA - 315nm to 400nm
UVB - 280nm to 315nm
UVC - 200nm to 280nm
List 7 common sources of UV light.
The sun
Germicidal lamps
High pressure mercury arc lamps
Special fluorescent lamps
Welding arcs
Sunlamps
Sunbeds
What radiation does the tear film generally absorb?
Some UVC
Wjat radiation do the cornea and conjunctiva absorb (2)? What does the anterior stroma absorb specifically?
UVB and UVC
Anterior stroma absorbs UVB
What radiation does the aqueous absorb (2)?
UVA and UVB
What radiation does the lens nucleus and epithelium absorb (3)?
UVA, some UVB, and some visible light
What radiation does the lens capsule absorb?
Negligible amounts
What ocular structure absorbs most UV radiation? Where is damage due to radiation usually limited to?
Corneal epithelium
-damage usually limited to this layer
What occurs with photokeratitis and does exposure have a cumulative effect? Who is it common amongst and what is it often referred to as (3)?
Reduced cell division, cell death and/or ulceration
Exposure has a cumulative effect
Also known as arc eye, welders flash, and snow blindness
How long does the latent period of photokeratitis last for? List 5 symptoms and note when discomfort disappears.
Latent period of 6 to 12h
FB sensation
Photophobia
Lacrimation
Blepharospasm
Lid oedema
Discomfort disappears in 48h
List 8 ocular signs of ultraviolet light radiation.
Lid oedema
Blepharospasm
Lacrimation
Oedema
Photophobia
Corneal erosions
Hyperaema
Erythema
List 6 components of assessing damage due to ultraviolet light.
History
VA
Slit lamp (lid eversion and staining)
AC
DFE
Photo