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OD3 (S1&2) > DIS - Eye Trauma IV: Radiation - Week 8 > Flashcards

DIS - Eye Trauma IV: Radiation - Week 8 Flashcards

1
Q

True or false
Artificial sources tend to emit radiation in excess of the suns radiation.

A

True

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2
Q

What two gases are responsible for absorbing most of the UV radiation from the sun? List three other important componrnts and what they absorb.

A

Oxygen gas and ozone
H2O, CO2, and dust help absorb some infrared

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3
Q

In terms of damage to tissue, what does the effect of EM radiation depend on (2)?

A

Wavelength and photon energy

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4
Q

What are the two distinct damage mechanisms of EM radiation? Note the wavelengths that generally cause each.

A

Thermal
-long wavelengths, low photon energy
-causes molecular agitation
Photochemical
-short wavelengths, high photon energy
-causes excitation, breaking chemical bonds

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5
Q

At what energy levels does ionisation begin to occur?

A

> 6eV

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6
Q

Note what wavelengths the following structures absorb (at ~90% transmittance):
Cornea
Aqueous
Lens
Vitreous

A

Cornea ~350nm
Aqueous ~400nm
Lens ~450nm
Vitreous ~500nm

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7
Q

What ocular structures absorb UVB and UVC (1)?

A

The cornea

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8
Q

What ocular structures absorb UVA (2)?

A

The lens and iris

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9
Q

What ocular structures absorb IRC (1)?

A

The cornea

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10
Q

What is the range of UV light? Note the range for each subcategory.

A

200nm to 400nm
UVA - 315nm to 400nm
UVB - 280nm to 315nm
UVC - 200nm to 280nm

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11
Q

List 7 common sources of UV light.

A

The sun
Germicidal lamps
High pressure mercury arc lamps
Special fluorescent lamps
Welding arcs
Sunlamps
Sunbeds

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12
Q

What radiation does the tear film generally absorb?

A

Some UVC

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13
Q

Wjat radiation do the cornea and conjunctiva absorb (2)? What does the anterior stroma absorb specifically?

A

UVB and UVC
Anterior stroma absorbs UVB

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14
Q

What radiation does the aqueous absorb (2)?

A

UVA and UVB

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15
Q

What radiation does the lens nucleus and epithelium absorb (3)?

A

UVA, some UVB, and some visible light

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16
Q

What radiation does the lens capsule absorb?

A

Negligible amounts

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17
Q

What ocular structure absorbs most UV radiation? Where is damage due to radiation usually limited to?

A

Corneal epithelium
-damage usually limited to this layer

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18
Q

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)?

A

Reduced cell division, cell death and/or ulceration
Exposure has a cumulative effect
Also known as arc eye, welders flash, and snow blindness

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19
Q

How long does the latent period of photokeratitis last for? List 5 symptoms and note when discomfort disappears.

A

Latent period of 6 to 12h
FB sensation
Photophobia
Lacrimation
Blepharospasm
Lid oedema
Discomfort disappears in 48h

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20
Q

List 8 ocular signs of ultraviolet light radiation.

A

Lid oedema
Blepharospasm
Lacrimation
Oedema
Photophobia
Corneal erosions
Hyperaema
Erythema

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21
Q

List 6 components of assessing damage due to ultraviolet light.

A

History
VA
Slit lamp (lid eversion and staining)
AC
DFE
Photo

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22
Q

What are the goals of managemeny for damage due to ultraviolet light? List 2 treatment options, noting dosages.

A

Prevent infection
Alleviate pain
Facilitate healing
Non-preserved tear supplements
-q5-10 mins for the first hour, then q1h to q3h
-broad spectrum antibiotic gtt (usually not needed)

23
Q

List 5 long term effects of UV radiation on the anterior eye.

A

Pterygium
Pingueculum
Nodular band-shaped keratopathy (climatic droplet keratopathy)
Cataracts
Tumours

24
Q

Is nodular band-shaped keratopathy a degenerative condition? What is the pathophysiology and does it begin peripherally or centrally?

A

Is degenerative

Accumulation of translucent material in superficial corneal corneal stroma within the interpalpebral region
Begins peripherally and spreads centrally

25
Q

Which type of UV light causes cataract?

A

UVB

26
Q

Is the retina protected in aphakes?

A

No

27
Q

Does UV exposure increase incidence of ARMD?

A

Some studies found it does
One found no association

28
Q

Describe how solar maculopathy occurs. Can small sungazes cause damage or is a long period required? What increases incidence (2)? Who is it most common amongst (3)?

A

A burn to the foveal area due to excess UV light
Sungazing for even 20 seconds can cause damage in some patients
Much higher incidence if solar eclipse or binocular/telescope use
Most common in drug users, alcoholics, and mentally unwell patients

29
Q

What is the range of visible light?

A

400nm to 780nm

30
Q

Does visible light cause photochemical or thermal damage to the eye, or no damage at all (2)?

A

Mostly photochemical damage
Even low levels can cause damage to PR and RPE
Thermal photocoagulation - occurs when high intensity light is focused on the retina

31
Q

Is there any evidence to suggest limiting blue light exposure is beneficial?

A

No

32
Q

What is the range of infrared light? Note the three categories.

A

780 to 10,000nm
IRA
IRB
IRC

33
Q

List 5 common sources of infrared light.

A

Sunlight
Arc lamps
Electrical fires
Glass and steel furnaces
Welding

34
Q

Note what infrared light the following structures absorb.
Cornea (1)
Lens (2)
Retina (1)

A

Cornea - IRC
Lens - IRB, IRA
Retina - IRA

35
Q

Give two corneal effects due to infrared exposure.

A

Opacification
Polymegathism

36
Q

What effect does indirect exposure of infrared light have on the lens and via what structure?

A

Anterior capsular cataract via inditect hrat transfer from the iris pigmented epithelium, which absorbs the light

37
Q

What effect does direct exposure of infrared light have on the lens (4)?

A

Posterior subcapsular cataract
Posterior cortical cataract
Cortex opacification
Lamellar splitting and exfoliation of the anterior capsule

38
Q

List 5 causes of retinal damage due to infrared exposure. What absorbs the infrared (2)?

A

Solar retinopathy
IR laser
Metal-arc inert gas welder
High intensity light sources (xenon gas lamps)
Medical lasers
-absorbed by melanin granules in the RPE and choroid

39
Q

What is the primary effect of microwaves and what ocular structure is particularly susceptible to it and why?

A

Increased tissue temperature
Lens particularly susceptible
-avascular
-cant dissipate heat

40
Q

What does the degree of microwave penetration depend on?

A

Wavelength

41
Q

What generally occurs when microwaves are applied to the lens and is it supported by epidemiology?

A

Posterior subcapsular cataracts in animal models
-nkt supported by epidemiology

42
Q

Briefly describe how a laser works.

A

Radiant energy is used to excite atoms, where electrons move to a higher energy level
As they return, they emit a specific energy of light

43
Q

What are two ocular effects of UV laser exposure? What about visible and IR lasers?

A

UV
-corneal epithelial damage
-cataracts
IR
-traumatic cataracts

44
Q

What mode of lasers can cause shockwaves?

A

Q switched high intensity beams

45
Q

List the four main classes of lasers and note which two can cause permanent damage.

A

1 and 1M
2 and 2M
3R and 3B
4
3B and 4 can cause irreversible damage

46
Q

What is ionising radiation? Give four examples.

A

Very short wavelengths
-cosmic rays
-radioisotopes
-xrays
-gamma rays

47
Q

Is daamage due to ionising radiation initially severe?

A

No

48
Q

Lisr four signs of ionising radiation damage.

A

Erythema
Skin damage
Corneal compromise
Cataracts

49
Q

Do thermal injuries to the eye often involve the globe? Explain.

A

No, mostly lids
Protected by blink reflex

50
Q

List three characteristics of ocular thermal injury.

A

Marked oedema
Tissue necrosis
Pain

51
Q

Is the globe commonly or rarely involved in flame burn injuries?

A

Rarely

52
Q

Why may epiphora occur with a flame burn injury?

A

Blocked puncta due to subsequent fibrosis

53
Q

Where do contact burns most often occur?

A

90% at home

54
Q

What is the management of a thermal burn (6)?

A

Clean and irrigate the site
Debride necrotic tissue
Prophylaxis and cold compresses
Antibiotic q2g for 1 day then q4h until healed
1 drop homatropine in office
Non-preserved tear supplements prn
Analgaesic (panadol forte)

OD3 (S1&2) (114 decks)

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