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Refractive > Incisional Techniques > Flashcards

Incisional Techniques Flashcards

1
Q

Radial incisions - where flattening

A

in both the meridian of the incision and the one 90° away

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2
Q

Tangential (arcuate or linear) - where flattening

A

in the meridian of the incision and steepening in the meridian 90° (may be equal to or less than the magnitude of the decrease in the primary meridian)

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3
Q

coupling

A

flattening in the meridian of the incision and steepening in the meridian 90° away

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4
Q

How deep should be the incision

A

85%–90% deep

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5
Q

In older effect is lower or grater

A

greater

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6
Q

Collagen Shrinkage - what temperature

A

58°–76°C

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7
Q

Thermokeratoplasty and conductive keratoplasty - where

A

in the midperiphery to cause local collagen contraction with concurrent central corneal steepening

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8
Q

Photoablation - laser energy sufficient to break

A

4 eV per photon or greater

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9
Q

Argon-fluoride (ArF) lasers - wavelength

A

193 nm with 6.4 eV per photon

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10
Q

Argon-fluoride (ArF) lasers - advantages

A

high energy per photon, very low tissue penetrance, capable of great precision

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11
Q

femtosecond laser - usage

A

creating flaps for LASIK and for the SMILE procedure, channels for intrastromal ring segments and for lamellar keratoplasty and PKP

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12
Q

femtosecond laser - wavelength

A

1053-nm infrared beam

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13
Q

femtosecond laser - phenomenon

A

photodisruption, a process by which tissue is transformed into plasma, and the subsequent high pressure and temperature generated lead to rapid tissue expansion and formation of microscopic cavities within the corneal stroma

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14
Q

Ho:YAG laser - wavelength

A

2.13 μm

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15
Q

Ho:YAG laser - phenomenon

A

Photothermal effects with a wavelength of 2.13 μm into the anterior stroma

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16
Q

Photothermal effects - for whom

A

low hyperopia

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17
Q

How to reduce glare, halos, and regression with Photoablation

A

optical zone should be 6 mm or larger

18
Q

Ablation - which layers

A

Bowman layer and the anterior stroma

19
Q

LASIK - which layers

A

stromal bed

20
Q

Flaps thickness

A

80 - 180 μm

21
Q

Broad-beam lasers

A

larger-diameter 7 mm, slower repetition, high energy, require a small number of pulses to ablate

22
Q

Scanning-slit lasers

A

narrow-slit, improving the smoothness, allowing for larger-diameter ablation zones

23
Q

Flying spot lasers

A

smaller-diameter beams (approximately 0.5–2.0 mm), higher repetition rate, majority of today’s lasers

24
Q

Most common aberrations follwing myopic corrections

A

spherical aberration and coma

25
Q

Wavefront-optimized laser ablation

A

taking the curvature of the cornea into account and increasing the number of peripheral pulses

26
Q

wavefront-guided

A

slower, expense of the aberrometer, treat both lower-order and higher-order, pupil-tracking system, treatment of highly aberrated eyes, such as eyes with previous RK or PKP

27
Q

greater tendency toward haze formation

A

deeper ablations, increased surface irregularity, and prolonged absence of the epithelium

28
Q

What drugs are contraindicated

A

Isotretinoin, amiodarone, sumatriptan for PRK and LASIK. hormone replacement therapy or antihistamines for PRK

29
Q

Tangential keratotomy and AK - where is incision

A

at the 7-mm optical zone

30
Q

Tangential keratotomy - use

A

was used in the past in combination with RK to correct myopic astigmatism

31
Q

AK and LRI - use

A

AK - post-keratoplasty astigmatism. AK and LRI - astigmatism during or after cataract surgery and IOL implantation, as well as after refractive surgery procedures such as LASIK and PRK

32
Q

When there is a coupling ratio greater than 1.0 - what occurs

A

hyperopic shift occurs

33
Q

Long, straight, and tangential incisions tend to induce a coupling ratio

A

greater than 1.0

34
Q

When a correction is less than 2.00 D of astigmatism, the coupling ratio is

A

typically 1.0

35
Q

when a correction is greater than 2.00 D of astigmatism, the coupling ratio tends to be

A

greater than 1.0

36
Q

AR or LRI change spherical equivalent?

A

no

37
Q

LRI - how deep incisions ?

A

600 μm depth, or 50 μm less than the thinnest pachymetry measurement at the limbus

38
Q

What can happen when moving from an upright to a supine position

A

15° of cyclotorsion can occur

39
Q

Where to make AK after KP?

A

in the graft or in the graft–host junction. . When AK incisions are made in the host, the effect is significantly reduced

40
Q

Irregular astigmatism is more common after AK or LRI?

A

more common with AKs

Refractive (12 decks)

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