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Z Lasers - Final > 1 - Asimellis > Flashcards

1 - Asimellis Flashcards

1
Q

Ophthalmic lasers provide good examples of 3 fundamental laser applications based on (4)

A

Total output energy
Output power
Photon energy
Spectral transmission

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2
Q

Vitreolysis

  • purpose/what it is
  • aka/layman’s term
A

A non-invasive procedure that can relieve the visual disturbance caused by symptomatic floaters via vaporization

Floater laser removal

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3
Q

Floaters

  • part of what happens in __
  • cause __ light scattering
A

Aging eye

Foward light scatter

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4
Q 
Vitreolysis
-laser/pulse type
—state
—lasing medium
—wavelength
A 
Low-energy nanosecond pulsed Nd:YAG
-solid state
-Nd:YAG crystal medium
-1064 nm (near IR)
—frequency doubled is 532 (green)
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5
Q

Photocoagulation

  • describe
  • temperatures
  • what happens to the tissue
A

Tightly focused energy interacts with tissue, slowly heats blood/tissue, destabilizing proteins and other biomolecules (bloodless in/excision)

As a blood clot forms, tissue coagulation of 50-100 C is photocoagulation

Shrinks the tissue due to water removal; the tissue is burned and neutered

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6
Q

Floaters

-most serious type

A

Weiss ring

  • created by PVD around optic nerve
  • often position selves right above macula
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7
Q

Vitreolysis

-other option

A

Vitrectomy (surgical replacement of the vitreous with an inert, translucent balanced salt solution via pars plana)

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8
Q

CPC = cyclophotocoagulation

  • describe
  • purpose
A

Cyclodestructive procedure that ablates the ciliary body epithelium

Lower IOP by decr fluid production (by detachments of CB)

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9
Q

CPC = cyclophotocoagulation
-variations:
—less invasive
—more precise

A

Transscleral CPC = less invasive

Endoscopic CPC = more precise

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10
Q

CPC = cyclophotocoagulation

-considerations (2)

A

A single tx may not achieve adequate IOP control, repeat tx may be needed

Occassionally results in excessive lowering of pressure

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11
Q

Retinal lasers

-laser used for PRP in pts with diabetic ret or retinal ischemia/NV

A

FD:YAG (532nm)

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12
Q

PRP

  • purpose
  • part of retina that absorbs the light
  • effect of absorption on retina
A

Retinal ischemia, retinal NV, NPDR

Pigment epi (RPE)

Denatures tissue protein via thermal burns (“bombards the retina”)
-scarring “welds” the retina to underlying tissue

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13
Q

PRP

-pathophys of how it helps with ischemia

A

Improves oxygenation

Destroys largely unused, ischemic extramacular retina -> reduces area of ischemic tissue -> reduces total VEGF production -> reducing impetus for NV

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14
Q

PRP for diabetic ret study

-results

A

Early PRP reduces risk of severe visual loss by ~23%

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15
Q

PRP

-retinal laser considerations

A

Anatomic effects - want to avoid complications due to dispersion of thermal energy within retina and choroid

Multispot pattern - greatly mitigated, but not eliminated these issues

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16
Q

The femtosecond laser

  • wavelength and pulse
  • energy
  • focus in eye
A

1053m (IR), 10^15 sec pulse (ultrashort)

Each photon = 1.17eV
-recall 3.5eV is threshold for biological tissue damage (UV)

IR can be focused anywhere within or behind the cornea (very low absorption from ocular tissue)

17
Q

The femtosecond laser

-2 major advantages vs longer pulses (e.g. nanosecond)

A

Reduced pulse energy necessary to induce ablation (due to power density)

Significant reduction of heat-affected zone -> improved contour/sharpness for laser-processed structures

18
Q

The femtosecond laser

-example of a sx it’s used for

A

Cataract removal = “femtosecond laser assisted caratact surgery”

19
Q

Laser vision correction

  • microns per D
  • residual bed
  • SE
A

~15 microns per D

Residual bed ~300 microns

Weakend cornea = HOA

20
Q

Laser vision correction

-myopia correction calculation

A

Munnerlyn formula:

Ablation depth = (optical zone)^2 * (myopia correction/3)

21
Q

Laser vision correction

-type of laser usually used

A

Excimer (photoablation)

22
Q

Excimer laser

  • state
  • lasing medium
  • wavelength
  • energy
A

Gas

Excited dimer - a noble gas and halide (EXCited diMER)

Depends on the molecules used, usually in UV (193nm)

6.4eV

23
Q

Steps of LASIK

A

Flap creation via femtosecond laser (~120nm)

Lift flap

Excimer laser ablation of tx area

24
Q

Steps of SMILE

A

2 lamellar cuts (creates a lenticule)

Lenticule separation and removal

25
Q

Other ophthalmic laser procedures
-PTK (phototherapeutic keratoplasty)
—should be limited to __

A

Anterior corneal pathology only

-deeper scars need deeper ablations, may result in haze or hyperopic shift

26
Q

Other ophthalmic laser procedures
-ASP (anterior stromal puncture)
—indication
—laser type

A

RCE

Nd:YAG

27
Q

Other ophthalmic laser procedures
-LSL (laser suture lysis)
—one of the most frequently employed techniques for post-op IOP control is __

A

Partial release of the flap by LSL

28
Q

Other ophthalmic laser procedures
-oculoplastic surgery
—laser

A

CO2

29
Q

Other ophthalmic laser procedures

-briefly, what is photomydriasis/photomiosis

A

Extension/reposition of the pupil

Laser coagulates are applied on iris circularly/within a region opposite to pupil displacement

30
Q

Other ophthalmic laser procedures

-anterior synechiolysis/synechiarrhexis

A

Elimination of iridolenticular synechiae after ct extraction with Nd:YAG

31
Q

Future of ophthalmic lasers

-one that he hit on

A

Blue femtosecond laser

Z Lasers - Final (4 decks)

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