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Optics Of The Eye Block 6 > Laser Vision > Flashcards

Laser Vision Flashcards

1
Q

What do lasers do

A

Evaporate, melt, break down tissue

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2
Q

The light emitted from a laser is _____________, that is, of one wavelength (color)

A

Monochromaticity

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3
Q

Properties of laser

A
  • monochromatic
  • directional
  • coherent
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4
Q

What are we concerned about in the 4 basic interactions of light when it comes to lasers?

A

Absorption

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5
Q

What is the number one ability of the ophthalmic lasers

A

Ability to be focused and absorbed by collagen

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6
Q

What are some things lasers are used for in ophthalmology

A
  • corneal refractive surgery
  • retina (photocoagulation)
  • lens (cataract)
  • Iris (glaucoma)
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7
Q

To open up an pacified lens capsule resulting from prior extracapsular cataract surgery

A

Posterior capsulotomy

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8
Q

Removal of corneal tissue by high energy photon directly breaking molecular bonds with sufficient photon energy

A

PhotoAblation by Excimer Laser

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9
Q

What is the photon energy of Excimer Laser

A

193nm, 6.4 eV energy

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10
Q

Biggest risk of lasers

A

Not reversible

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11
Q

Importance of pulsed laser

A

Molecular breakdown

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12
Q

The nano-second pulsed laser

A

Makes craters here, doesn’t melt!

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13
Q

What does lasik stand for

A

Laser-assisted-in-situ keratomileusis

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14
Q

Steps of LASIK

A
  1. Flap created in 100 microns of cornea
  2. Lift flap
  3. Excimer laser ablation
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15
Q

Why is LASIK better for the patient than PRK?

A

LASIK goes underneath the epithelium and then puts the epithelium back over it for protection. PRK strips the top most layer, causing a lot of pain for patient in the first few days

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16
Q

What does SMILE stand for

A

Small-incision lenticulate extraction

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17
Q

Steps of SMILE

A
  1. Lamellar cut
  2. Lenticular creation
  3. Lenticular separation
  4. Lenticule removal
  5. Reshape cornea

NO LASER

18
Q

To correct myopia, we want

A

Less optical power

19
Q

Less corneal power means

A

Decreased corneal curvature (flatter)

20
Q

What we want when you correct myopia with laser-vision correction

A

Less optical power and decreased curvature

21
Q

What we can do to correct myopia in laser-vision correction

A

Flatten the cornea

Remove the central tissue

22
Q

What part of the eye do we hit with the laser?

A

Optical zone

23
Q

What is the golden standard for laser surgery

A

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

24
Q

To correct myopia we want

A

Less optical power

25
Q

Less corneal power means

A

Decreased corneal curvature (flatter)

26
Q

What do we want when correcting myopia

A 
Less optical power
Decreased curvature (center)
27
Q

What can we do to correct myopia

A

Flatten the cornea

Remove the central tissue

28
Q

What part of the cornea do we want to flatten when laser correcting for myopia

A

Optical zone that is the size of a scoptopic pupil

29
Q

What shape do we move from the cornea when we correct for myopia

A

Positive meniscus, reduced optical power

30
Q

Munnerlyn formula

A

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

31
Q

For hte same myopia correction, consider increasing the optical zone by a factor of the square root of 2. The maximum ablation depth…

A

Increases by a factor of 2

32
Q

Two myopic eyes, -2.00 and -6.00. The maximum ablation depth in the -6.00 eye, compared to the -2.00 eye is

A

More by a factor of 3

33
Q

Pre op and post op LASIK corneal curvature in myopia

A

Post op the corneal curvature will be flatter in someone being corrected for myopia

34
Q

To correct hyperopia, we want

A

More optical power

35
Q

More corneal power means

A

Increased corneal curvature (steeper)

36
Q

What do we want when correcting for hyperopia?

A 
More optical power
Increased curvature (center)
37
Q

What can we do when laser correcting for hyperopia

A

Steepen the cornea

Remove peripheral tissue

38
Q

What is the shape of the tissue that is removed from the hyperopic eye during laser correction?

A

Minus meniscus

39
Q

What does the ablation profile look like in hyperopia post op

A

Doughnut

40
Q

What happens to the CCT in hyperopia after laser surgery?

A

Nothing, the CCT is the same because the peripheral tissue is what was removed

41
Q

The corneal curvature went from 41.5 to 49.9, what is the degree of hyperopia that was corrected?

A

6-7 degrees of hyperopia

Optics Of The Eye Block 6 (7 decks)

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