XM 1 Flashcards by Cole Barnhart

What are the 3 types of effects that occur as a result of use of therapeutic lasers?

Thermal effects
Ionization effects
Photochemical effects

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What FDA class of lasers are the lasers used for eye procedures?

Class IV

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What FDA class of lasers are those used in printers, CD players, and DVD players?

Class I

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What FDA class of lasers are those used in barcode scanners?

Class II

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What FDA class of lasers are pointers?

Class III

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Starting with which FDA class of lasers are immediate skin and eye injury possible?

Class III

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What is considered the “safe” limit of laser power?

5 mW

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Interactions of light on biological tissue depend on what 3 characteristics?

Wavelength
Pulse duration
Irradiance (power per unit area)

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What is the end result of photocoagulation caused by laser light?

Denatured proteins

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What rise in temperature will cause photocoagulation of tissue?

10-20 degrees Celsius

(results in tissue temperature between 50 and 60 C

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What effect of therapeutic lasers is associated with the “thunderclap” and results in tissue damage?

Photodisruption (Ionizing Effect)

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What temperature range does photovaporization occur in?

60-100 degrees Celsius

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What temperature range does photodisruption occur in?

100-305 degrees Celsius

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What are 2 examples of thermal effects?

Photocoagulation

2. Photovaporization

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What is 1 examples of an ionization effect?

Photodisruption

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What are 2 examples of photochemical effects?q

Photoradiation

2. Photoablation

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What are 6 modes of laser operation?

Continuous wave (CW) lasers
Pulsed lasers
Q-switched lasers
Mode-locked lasers
Fundamental systems
Multimode systems

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At what temperature do visual changes begin occurring in the retina?

60 degrees Celsius

Blanching begins to occur due to coagulation

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At what temperature does a smoke plume result in the retina?

100 degrees Celsius

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What is PDT?

Photodynamic Therapy

Same thing as photoradiation

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What does photoablation do in layman’s terms?

Vaporizes the tissue by breaking bonds that bind the tissue together

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What are 2 examples of lasers that interact with photothermal effects?

Argon laser

2. Nd: YAG Laser

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What is 1 example of a laser that interacts with photoablation?

Excimer laser

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What is 1 example of a laser that interacts via photoradiation?

Photodynamic therapy

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What is 1 example of a laser that interacts with tissue via photodisruption?

Nd: YAG laser (Q-Switched)

What are 3 methods of laser delivery?

1. Biomicroscope (Slit Lamp) 2. Binocular Indirect Ophthalmoscope (BIO) 3. Endophotocoagulation (enter through pars plana)

What is an argon blue-green laser composed of?

70% blue (488 nm) | 30% green (514 nm)

What is the wavelength of a green argon laser?

514.5 nm

What is the wavelength of an Nd-YAG laser?

532 nm

What is the wavelength of a yellow laser?

577 nm

What is the wavelength of a krypton red laser?

647 nm

What is the wavelength of a diode laser?

805-810 nm

What is a large benefit of the MicroPulse laser design?

Long off times allow tissue to cool which results in less thermal damage to the retina

What does duty cycle mean as applied to MicroPulse lasers?

Example: 5% duty cycle | On for 5 units of time, off for 95 units of time

What is a major advantage of the green argon laser?

No absorption by macular pigment

What laser is preferred over green argon lasers to treat choroidal neovascularization?

Yellow argon laser

What are the 10 layers of the retina from inner (vitreous) to outer (choroid)?

1. (ILM) Internal limiting membrane 2. (NFL) Nerve fiber layer 3. (GCL) Ganglion cell layer 4. (IPL) Inner plexiform layer 5. (INL) Inner nuclear layer 6. (OPL) Outer plexiform layer 7. (ONL) Outer nuclear layer 8. (ELM) External limiting membrane 9. (PR) Photoreceptors 10. (RPE) Retinal pigmented epithelium

What membrane lies directly outside of the RPE?

Bruch's membrane

For the laser to remain effective, an increase in spot size needs an increase in what?

Increase in power

What are the 2 types of laser delivery system?

1. Parfocal system | 2. Defocus system

Where will a parfocal system be focused for treatment?

On the retina

As parfocal spot size increases, does the diameter of the laser at the cornea increase or decrease?

Decreases | More risk of damage

Where will a defocus system be focused for treatment?

On the retina or behind the retina

What would occur if a defocus system was focused in front of the retina?

Vitreous damage or lens damage

What is an advantage to the defocus system and when would it be utilized?

Corneal beam density decreases as spot size increases (Lower risk of damage) Useful for when large spot size is required

What is the scale of photocoagulation lesions graded as? Which is most mild? Most severe?

1-4 1 is most mild (light, minimal constriction) 4 is most severe (heavy, total constriction, charring)

How are punctate and streaked coagulation patterns different?

Punctate style patterns appear as dots | Streaked style patterns appear as dashes

What is the anatomic center of the fovea known as?

Umbo

What is the molecule that causes neovascularization in diabetic retinopathy?

VEGF

What is the name of the laser treatment for diabetic retinopathy?

Panretinal Photocoagulation

What do black spots in the retina after laser treatment signal?

RPE has been damaged

What is peripheral laser iridotomy used to treat?

Either primary or secondary angle closure glaucoma

What 2 types of lasers are useful for performing Peripheral Laser Iridotomy procedures?

1. Argon lasers | 2. Nd: YAG lasers

What type of laser is used to perform PRP?

Argon Green | PASCAL (Pattern Scanning Laser)

What is the purpose of the PLI procedure?

Creates an opening in the peripheral iris to allow aqueous to pass through

Where is the opening in the iris typically made in peripheral laser iridotomy?

Underneath the upper lid

What is the purpose of laser trabeculoplasty?

To treat the trabecular meshwork to improve the outflow of aqueous

What are the 4 types of laser trabeculoplasty?

1. (ALT) Argon Laser Trabeculoplasty 2. (SLT) Selective Laser Trabeculoplasty 3. (MLT) Micropulse Laser Trabeculoplasty 4. (TSLT) Titanium Sapphire Laser Trabeculoplasty

Which type of laser trabeculoplasty is not commonly used anymore because of trabecular meshwork damage?

Argon Laser Trabeculoplasty (ALT)

When is laser trabeculoplasty typically performed?

As a last resort, once patient is on maximum medical therapy.

What is the purpose of ALT?

To scar the trabecular meshwork to increase the amount of aqueous outflow

Where is the ALT laser aimed, and how many degrees around is the first treatment?

Junction of pigmented and nonpigmented TM | 180 degrees

What is the target and goal of SLT treatment?

Targets melanin in pigmented TM | Recruits macrophages to help with outflow

Does previous ALT treatment have any effects on the results of SLT treatment?

No | IOP reduction is not influenced by previous ALT

How long after SLT do the biochemical changes take place?

4-6 weeks | Delayed response

What is the main goal of MLT?

Simulate a biological response in the TM while minimizing damage to the tissue

Between ALT, SLT, and MLT, which procedure involves the smallest laser spot size?

ALT | About 50 microns

How does the spot size of MLT compare to that of SLT?

Slightly smaller 300 microns as opposed to 400 microns Allows access to narrower angles

Is ALT a repeatable procedure?

Are MLT and SLT repeatable procedures?

Yes

Where is the laser focused in a YAG laser capsulotomy?

Slightly behind the lens in the vitreous

What is the purpose of YAG laser capsulotomy

Opens the opacified posterior capsule to improve patient VA and allow easier viewing of the fundus

Is an IOP spike normal to see following YAG laser capsulotomy?

Yes

What is the normal size of the opening of the posterior capsule created in YAG laser capsulotomy?

4mm

What is the average number of laser spots per eye in panretinal photocoagulation?

1200 laser spots per eye

Topical anesthesia allows for the delivery of about how many laser spots with PRP?

500-600 spots

What type of anesthesia allows for the delivery of a full treatment (1200) of laser spots in PRP?

Retrobulbar anesthesia

What is the purpose of PRP?

Kill/destroy living retina that is releasing VEGF due to being in a hypoxic state

How far around the posterior pole (macula and optic disc) are the laser spots delivered with PRP?

3 disc diameters around posterior pole and extend to the equator

What is the purpose of lasering around a retinal break?

Seals off the progression of sub-retinal fluid (SRF) that would lead to macular involvement

What is a risk of laser treatment of retinal tears?

Vitreous shrinkage may tear the retina farther | Shrinkage may occur with opacities present

XM 1 Flashcards

(81 cards)