Final Review Flashcards
1
Q
what does LASER stand for
A
Light amplification of stimulated emission of radiation
2
Q
Characteristic properties of photons
A
- in the interaction of radiation with matter, radiation behaves like particles called photons. PHOTONS=PARTICLES
- photons are always moving with the speed of light in a vacuum. Attempt to stop a photon=absorption
- photons travel in straight lines
- photons have a zero rest mass but never occur at rest
3
Q
Electron volt
A
Energy carried by a single photon
-the amount of energy that an electron gains while moving through a potential difference of 1 V
4
Q
Electrons that orbit the atomic nucleus exist
A
ONLY IN DISCRETE ENERGY LEVELS
Bohr atom model
5
Q
An electron can jump to a _____ energy level by emitting a photon
A
Lower
Bohr
6
Q
A electron can jump to a _____ energy level by absorbing a photon
A
Higher
Bohr
7
Q
Spontaneous emission
A
- An electron that stays in an excited state for <8-10s and then jumps to a LOWER LEVEL emitting a photon in the process
- an atom will absorb only photons whose energy is the exact amount needed to raise electrons up by 1 energy level and will release that same wavelength of enegery as we photon
8
Q
Stimulated emission
A
If a photon of the precise wavelgnth passes Ana electron in an elevated energy level of equal gain in energy, that electron will emit a photon of that same wavelgnth, direction, phase, coherence, and polarization
Two photons will leave for each photon that enters=amplifying the beam
9
Q
Fluorescence and Phosphofluorescence
A
- stand out because the luminous flux EMITTED at the fluorescent wavelengths by a fluorescent substance may be FAR GREATER than the luminous flux INCIDENT at those wavelengths
- the energy that drives the fluorescent radiation comes from an incident HIGHER FREQUENCY radiation (UV)
- when a metastable state with a long lifetime is populated by incident radiation, the material may continue to glow or emit radiation long after the original source is removed
10
Q
What is the distinction between fluorescence and phosphofluoresence
A
Matter of time
11
Q
Population inversion: electrons at LOWER energy levels ____protons
A
Absorb
12
Q
Population inversion: electrons at HIGHER levels _____protons
A
Emit
13
Q
Application occurs when
A
Mor eeelctrons are at an elevated state than at a lower energy state
14
Q
Cavity oscillator
A
- optical cavity
- 2 parallel Mirrors=feedback loop with active medium between the mirrors. Mirrors have optical coating-reflective proptosis
- builds the strength of the avalanche
- stimulated emission causes application of the signal within the optical resonator
15
Q
Q switching
A
- NANOSECOND DURATION
- higher power intensity
- shutter or light modulator
- energy builds and is then released in sudden bursts
- plasma formation
- PHOTODISRUPTIVE EFFECT
- less affected by pigmentation
16
Q
Laser light characteristics
A
Coherence
Monochromatic
Collimated
17
Q
Photochemical effects
A
Photoradiation
Photoablation
18
Q
Photoradiation
A
- Photochemical
- IV administration of photosensitizing agent taken up by target tissue-free radicals
- PDT therapy
19
Q
Photoablation
A
Photochemical
- pigment independent
- higher energy UV light=excimer laser (cleaves bonds)
- NON THERMAL
20
Q
Photothermal effects
A
Photocoagulation
Photovaporization
21
Q
Photocoagulation
A
Phototheramal
- ALT
- targets melanin and hemoglobin
- denatures protein, contracts collagen, coagulates blood
- 10-20 decrease C increase in temp
22
Q
Photovaporization
A
Photothermal
- targets melanin
- water turned into steam, tissue turned to CO2 and H20
- 60-100* C increase in temp
23
Q
Mechanical disruption
A
Photodisruption
24
Q
Photodisruption
A
- mechanical disruption
- YAG CAP/LPI/VITREOLYSIS
- reduces tissue to plasma, modules stripped of electron. NO COAGULATION** (why there is blood on LPI with Nd:YAG 1064 vs using Argon)
- PIGMENT INDEPENDENT
- explosive force
- pulse travels back towards surgeon
- 15,000* C increase in temp
25
Pigment dependent lasers
Argon
| Diode
26
Pigment independent laser
Nd:YAG 1064nm
Femtosecond
Excimer
27
Nd:YAG characteristics
- 1064nm
- solid state laser (level 4)
- Q switched
- continuous or short pulsed
- neodymium YAG
- photodisruptive
28
Nd:YAG 532
- 532nm
- Freqyency doubling and Q switches
- photocoagulation/sublethal photostimualtion pigment dependent
29
UV range
200-400
30
UVC
200-280
31
UVB
280-315
32
UVA
315-400
33
Visible light
400-780
34
IRA
780-1400
35
IRB
1400-3000
36
IRC
3-1000um
37
Near infrared
IRA
| 780-1400nm
38
Far infrared
IRB and IRC
1400-3000nm
3-1000um
39
UV light absorbed within the
Cornea
| <400nm
40
Visible light absorbed with in the
Retina
| 400-700
41
Near infrared light absorbed within the
Retina
| 700-1400
42
Far infrared light absorbed within the
Cornea
| 1400nm+
43
Tissue variables
Melanin
Hemoglobin
Xanthophyll
44
Melanin
- absorbs across entire visible spectrum
| - absorbers infrared less effectively
45
Hemoglobin
Absorbed green and blue wavelengths very well
46
Xanthophyll
Absorbs blue well
| Use red or IR for macula
47
Class I ANSI standard
Very low powered laser (<0.5 uW)
- no eye or skin hazard from full day exposure
- no labeling requirements are needed
- lasers inside CD/DVD players
48
Class II ANSI standard
Low powered laser (<1mW)
- no eye hazard from intrabeam exposure within short period of time
- basic laser pointers/surveying lasers
49
Class IIIa
- visible beam with power <5mW
- damage on accidental exposure through optical aid
- more powerful laser pointers
50
Class IIIb
- Eye and skin hazard
| - viewed only through diffuse reflection from distance over 50mm for <10s with diffuse image diameter greater than 5.5mm
51
Class IV lasers
- eye andskin hazard from intrabeam and diffuse relcfection
| - fire hazard
52
What class is an Nd:YAG 532nm (freq doubled)
Class IIIb
53
Which class of lasers is an Nd:YAG 1064
Class IV
54
Laser safety
Governing bodies and professional organizations
-ANSI,FDA, OSHA
Administrative controls
-laser safety officer
Practice guidelines
-american society for laser medicine and surgery (ASLMS)
Protective equipment
-warning signs, skin protection, smoke evacuation
55
What grading system uses Roman numerals to describe the degree to whch the angle is closed
Sheie’s system
56
Which grading system uses numeral to describe the degree to which the angle is open
Shaffer
57
Which are pathological? Iris processes or peripheral synechiae
Synechiae
58
What is the general mechanism of action for a laser trabeculoplasty
Increase Aqueous outflow mainly through the TM
59
Indications for laser trabeculoplasty
```
POAG
NTG
OHTN
PDG
PSG
```
60
Positive predictors for laser trabeculoplasty
<40yo
Moderate to heavy TM pigment
Clear cornea
61
Thermal relaxation time
Time required by melanin to convert electromagnetic energy into thermal
-1 MICROSECOND
62
Argon laser trabeculoplasty: mechanical or biological MOA?
Both
63
What are the pre op drops for ALT and SLT
Alphagan 15-30m prior
| Proparacaine
64
Can you repeat an ALT
Highly recommended NOT to-increases complication and 50% need filtration surgery to lower IOP within 6 months of repeated ALT
65
SLT: mechanical or biological MOA?
Biological only
66
Is SLT a cold or hot laser and why
Cold
| Thermal relation time is not met, so no burns occur
67
Is SLT a safe and effective initial therapy?
Yes
| -based upon multiple studies
68
SLT laser settings
```
Energy-0.8-1.2mJ
Spot size-400microns fixed
Duration-3ns fixed
Pulses-1
Amount of burns ~100/360
```
69
What are the post opt drops of SLT
Alphagan
| NO STEROIDS!! Oral Tylenol PRN or optical NSAID if absolutely needed
70
What is the time frame for an SLT to be the most successful
12-60m
| -80% @ 1 yearand 50% at 5 years
71
Will an SLT be successful if the patient DI not repsond to a PGA
No
| Alvarados insights
72
Should you perform an SLT on patient’s with pigment dispersion syndrome/glaucoma?
Yes-be more cautious
| -10-20* at a time-test area
73
Can you repeat an SLT
Yes
| -no as effective the second time
