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C.EyeMD > CR.efractive > Flashcards

CR.efractive Flashcards

1
Q

Leading cause of dissatisfaction after surgery

A

Patient expectations

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2
Q

Preferred for active patients or patients prone to trauma

Surface laser procedure vs lamellar procedure

A

Lamellar procedure

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3
Q

Recommended time to wait before refractive surgery is done in pregnant and nursing women

A

3 months after delivery and cessation of nursing

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4
Q

When is refraction considered stable?

A

Less than 0.5 change in refraction per year

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5
Q

How long should CTL be removed prior to refraction?

A

3 days to 2 wks for soft
At least 2 weeks for rigid
At least 4 weeks for PMMA

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6
Q

Optical zone should be (greater, lesser) than pupil diameter

A

Greater

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7
Q

What is the minimum residual stromal bed thickness?

A

250 um or greater than 50% of original thickness

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8
Q

What is residual stromal bed thickness?

A

CCT minus (flap thickness plus ablation depth)

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9
Q

Systemic contraindications of refractive surgery

A

Uncontrolled autoimmune and immune mediated diseases
DM
Pregnancy and lactation
OCPs
Controlled autoimmune ds
Systemic meds - isotretinoin, amiodarone, sumatriptan

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10
Q

Absolute ocular contraindications of refractive surgery

A

Keratoconus and corneal ectasia
Insufficient corneal thickness for proposed ablation depth
Significant cataracts
Uncontrolled glaucoma
Uncontrolled external eye disease (bleph, MGD, dry eye, atopy or allergy)

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11
Q

Relative ocular contraindications for refractive surgery

A 
Monocular
Excessively steep or flat cornea
Forme fruste keratoconus and irregular astigmatism
HSV keratitis
Uncontrolled dry eye
Amblyooua
Scarring
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12
Q

Why is dry eye a contraindication to Ref Sx?

A

Normal tear film needed for corneal healing

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13
Q

Why is herpes contraindicated for Ref Sx?

A

Trauma from lamellar dissection and UV light may increase viral shedding and recurrence

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14
Q

Why is keratoconus contraindicated for Ref Sx?

A

Flap creation and removal of corneal tissue may increase ecstatic progression

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15
Q

Why is glaucoma a contraindication of Ref Sx?

A

Acute IOP rise when suction is applied to create flap

LASIK and surface ablation may influence IOP

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16
Q

What should be done for high myopes who want to undergo lasik?

A

Do lasik if no contraindications

Monitor posterior pole since still at risk for RD

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17
Q

LASIK in post retina surgery patients

A

Conjunctival scarring may interfere with suction placement

May be better to do PRK or LASEK

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18
Q

True or false

Refractive surgery for hyperopia is proven to reduce accommodative ET

A

False

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19
Q

Ref Sx issues in DM patients

A

Inc incidence of epi defect and epi in growth

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20
Q

Types of corneal refractive procedures

A 
Incisional
Laser ablation
Lamellar
Corneal implants
Corneal shrinkage
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21
Q

Types of lenticular Ref Sx procedures

A 
Phakic IOL
Cataract sx
Clear lens xg
Accommodative and pseudoaccommodative IOL implantation
Piggy back IOL implantation
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22
Q

In this procedure, corneal flap is made using a microkeratome.

A

LASIK

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23
Q

In this procedure, for corneal epithelium is removed.

A

PRK

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24
Q

In this procedure, corneal epithelium is peeled off then placed back

A

LASEK

Using alcohol, lasek laseng

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25
Q

In this procedure, microkeratome is used to make an epithelial flap

A

Epi-lasik

Take note, epithelial flap only

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26
Q

In this procedure, NdYAG laser is used to create corneal flap

A

Femto-LASIK

High energy with low pulse

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27
Q

Incisional procedures for myopia and myopic astigmatism

A

Radial keratotomy
Astigmatic keratotomy
Limbal relaxing incisions

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28
Q

Laser procedures for myopia

A

PRK

Lasik

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29
Q

Other options for myopia (not incisional or laser)

A

Corneal implants

Non laser procedures

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30
Q

Name the procedure described:
8 radial incisions placed in cornea, resulting in forward bowing of mid-peripheral cornea and compensatory flattening of Central cornea
Useful for myopia of -2 to - 8.75D
85 to 90% depth

A

Radial keratotomy

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31
Q

How does the optical zone diameter and incision depth affect the outcome of RK?

A

Smaller optical zone diameter and deeper incision - more flattening

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32
Q

When does refraction stabilise after RK?

A

After 3 months

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33
Q

Complications of RK

A 
Loss of BCVA
Delayed bacterial keratitis
Corneal scarring
Irregular astigmatism
Epithelial erosions
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34
Q

Types of Astigmatic keratotomy

A

Transverse (straight)
Arcuate (curved)
LRI

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35
Q

In Astigmatic keratotomy, where is flattening and steepening observed?

A

Local flattening

Steepening 90 degrees away

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36
Q

What is the effect of LRI on spherical equivalent?

What is the coupling ratio of LRI?

A

None

1.0

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37
Q

What does the value of the coupling ratio signify?

A

It signifies the effect of the procedure on the spherical equivalent.

If 1.0 - unchanged
More than 1.0 hyperopic shift

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38
Q

What is the Coupling Ratio of a transverse incision in Astigmatic Keratotomy?

A

Greater than 1

Hyperopic change

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39
Q

Characteristics of Arcuate keratotomy

A

95% depth
Mid-peripheral cornea
Greater correction with longer, deeper and more central incisions

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40
Q

Up to how much of astigmatism can LRI correct?

A

4D

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41
Q

Type of AK where limbal incisions are made. May be done in combination with wedge resection or suturing in the flat meridian.

A

LRI

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42
Q

Type of laser used for PRK

A

193 nm argon fluoride excimer laser

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43
Q

Methods of epithelium removal for PRK

A

Laser
Blade
Diluted ethanol
Cellulose sponge

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44
Q

Methods to remove epithelium for PRK?

A

Laser
Blade
Diluted ethanol
Cellulose sponge

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45
Q

Why is MMC used for PRK?

A

To prevent haze

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46
Q

What is LASEK?

A

Laser subepithelial keratomileusis

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47
Q

What is epi-LASIK?

A

Epithelial laser in situ keratomilieusis

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48
Q

LASEK and Epi-LASIK are examples of ________ procedures.

A

Surface ablation.

Epithelium is preserved.

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49
Q

Method of removal of the epithelium for LASEK

A

20% alcohol for 20 seconds

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50
Q

How is the epithelial flap created for Epi-LASIK?

A

Microkeratome is used. More viable epithelial cells.

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51
Q

True or false

Epi-LASIK and LASEK have been proven to be advantageous over PRK in reducing corneal haze.

A

False

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52
Q

How is mitomycin used for LASEK?

A

0.02% or 0.2 mg/ml for 12 seconds to 2 minutes

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53
Q

Options for pain management post ablation

A

Oral narcotics or NSAIDs
Topical anesthetics
Topical NSAIDs (but may slow re-epithelialization and promote sterile infiltrates)

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54
Q

What is LASIK?

A

Laser in situ keratomileusis

Two stage process that combines lamellar surgery with laser application

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55
Q

Options for lamellar flap creation in LASIK?

A

Microkeratome - bladed

Pulsed laser - bladeless; all laser

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56
Q

Advantages of LASIK

A

Faster visual recovery
Less postop discomfort
Safe
Effective

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57
Q

Range of effectivity of LASIK for spherical and cylinder?

A

Spherical - 10 to + 4

Cylinder up to 4D

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58
Q

How does the suction ring size affect the size of the flap?

A

The thicker the vertical dimension of the suction ring and the smaller the diameter of the ring opening, the less the cornea will protrude resulting to a flap with a smaller diameter.

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59
Q

Advantages of femto-LASIK

A

Better depth control
Lower flap complications
Lower rate of epithelial ingrowths
Less increase in IOP required
More control over flap diameter and centration
Very low risk for epithelial defects on flap
Less risk for free cap and buttonhole
More reliable flap thickness
Less chance for hemorrhage from limbal vessels
Ability to retreat immediately if incomplete ablation

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60
Q

Disadvantages of femtosecond laser

A

Longer suction time
More flap manipulation
Opaque bubble layer may interfere with ablation
Bubbles in AC may interfere with tracking and registration
Increased overall treatment time
Difficulty lifting flap after 6 mos
Increased risk of DLK
Increased cost
Requires new skills
Delayed photosensitivity or good quality plus photosensitivity, may require prolonged steroids

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61
Q

Post LASIK regimen

A 
Antibiotics (dc after 1 wk, but longer for femto) 
Steroids
NSAIDs
Ensure flap allignment
SCTL
Protective goggles up to 1 week
Lubricants
Avoid swimming and hot tubs for 2 weeks
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62
Q

Contraindications of LASIK

A

Forme fruste keratoconus and irregular corneas
Thin corneas (CCT less than 500um, RSB less than 250 um)
Orbital and lid anatomy that precludes use of microkeratome and femto laser
Poor epithelial adherence
Significant dry eye
Significant occupational and recreational risk for trauma

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63
Q

Difference of PRK vs LASIK in terms of laser beam area of application

A

PRK - applied on cornea

LASIK - applied under corneal flat

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64
Q

Difference of PRK vs LASIK in terms of recovery

A

PRK - 1 to 2 weeks

LASIK - within 12h

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65
Q

Difference of PRK vs LASIK in terms of post op eye drop use

A

PRK - 3 mo

LASIK - 1 wk

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66
Q

Disadvantage of PRK vs LASIK

A

Post op discomfort

Higher risk for haze

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67
Q

Disadvantage of LASIK vs PRK

A

Steeper learning curve

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68
Q

Efficacy of PRK vs LASIK

A

70% vs 98%

69
Q

Synthetic materials embedded in the corneal stromal lamellar, shortening the corneal arc length

2 segments of 150 degs of arc

A

Intrastromal corneal ring segments aka Intacs or Ferrara rings

70
Q

Range that Intacs can correct

A

-1 to - 3 D

Thicker segment, greater flattening

71
Q

Advantages of intacs

A

Can be explained and replaced

72
Q

Selection criteria for Intacs

A

21 years or older
Stable refraction for at least 12 mos
At most 1D astigmatism

73
Q

Contraindications for intacs

A

Collagen vascular, autoimmune, immunodeficiency diseases
Pregnant and nursing
Ocular conditions predisposing to future complications

74
Q

Stromal depth of intacs

A

68 to 70%

75
Q

Complications of intacs

A 
Loss of BCVA
AC perforation
Microbial keratitis
Implant extrusion
Shallow ring segment placement
Corneal thinning over intacs
Reduced corneal sensitivity
Induced astigmatism
Incision site NVs
Persistent epithelial defect
Iritis
Uveitis
Difficulty with night vision
BOV
Diplopia, Glare, Halos, fluctuating vision, photophobia
76
Q

Incisional procedure for hyeropia

A

Hexagonal keratotomy

77
Q

Laser procedures for hyperopia

A

LASIK

PRK

78
Q

Thermal procedures for hyperopia

A

Conductive keratoplasty

79
Q

How does hexagonal keratotomy work?

A

Circumferential connecting hexagonal peripheral cuts around a clear 4.5 to 6 mm optical zone
Allows central cornea to steepen thereby decreasing hyperopia

80
Q

How does PRK and LASIK work for hyperopia?

A

Flattens paracentral cornea resulting to a steeper central cornea. Works for up to 4 to 6D but with lower predictability and stability.
Longer postop stabilisation. Efficacy 94% for LASIK, 90% for PRK.

81
Q

Used for mild to moderate hyperopia with minimal astigmatism and presbyopia in the non-dominant eye

A

Conductive keratoplasty

82
Q

Uses a special probe to deliver RF wave energy to the deep stroma of the mid-peripheral cornea, causing focal shrinkage of collagen fibers, thus steepening the central cornea; can reach around 58 to 76 deg C

A

Conductive keratoplasty

83
Q

Disadvantage of conductive keratoplasty

A

Higher incidence of regression

Lack of adequate refractive effect

84
Q

Contraindications of conductive keratoplasty

A 
Pregnant
Keratoconus
Keloid formation
Narrow Angles
Implantable electronic devices
peripheral pachymetry reading measured at 6mm zone of less than 560 um
85
Q

Advantages of CK over LASIK and PRK

A 
no cutting involved
central cornea untouched
no tissue removed
no dry eye
safe
86
Q

Disadvantages of CK

A

only up to 3D correction
can’t treat patients with significant astigmatism
not as precise
regression

87
Q 
\_\_\_\_\_\_\_\_\_\_ treatment for presbyopia:
monovision
conductive keratoplasty
IOL implants
custom/multifocal ablations
corneal inlays
A

non-accomodative

88
Q

_________ treatment for presbyopia:
scleral weakening/expansion bands
accommodating IOL’s

A

accommodative

89
Q

Methods to achieve monovision in presbyopic patients

A

CTL, LASIK, surface ablation, CK, lens surgery

90
Q

Usual target refraction for monovision

A

Up to -1.5 to -2.5 D

91
Q

Usual target refraction for mini-monovision

A

-0.5 to -1.5 D

92
Q

How is monovison achieved in presbyopic patients?

A

Myopia is undercorrected
Hyperopia is overcorrected
Mild myopia is induced in emmetropic patienht

93
Q

What is the principle behind the use of CK for presbyopic patients?

A

Induction of mild myopia

94
Q

What is the problem if post-LASIK patients develop cataract?

A

Problematic computation of IOL power

95
Q

What is the problem if post-LASIK patients would require retina surgery?

A

Eye prone to flap problems including dehiscence, micro and macrostriae

96
Q

Usual indications for corneal transplantation after LASIK

A

Scarring, irregular atsigmatism, corneal ectasia, corneal edema

97
Q

True or false

CTL cannot be used by post-LASIK patients

A

False

98
Q

What is the problem if post-LASIK patients would develop glaucoma?

A

IOP measurements are unreliable

99
Q

Used to correct high ametropia beyond laser range

A

Intraocular refractive surgery

100
Q

Used to treat moderate refractive errors in patients wth thin corneas or atypical corneal topographies?

A

Intraocular refractive surgery

101
Q

Advantages of intraocular refractive surgery

A 
Refractive accuracy
Rapid visual recovery
Reversibility
Accommodation
Conservation of corneal sphericity
102
Q

Disadvantages of intraocular refractive surgery

A

Endothelial Cell loss
chronic inflammation
glaucoma

103
Q

Types of intraocular refractive sx

A 
Phakic IOL implantation
cataract surgery
clear lens extraction
accommodative and pseudoaccommodative IOL implantation
piggyback IOL implantation
104
Q

What is a phakic IOL?

A

An implantable collamer lens.

105
Q

Examples of phakic IOL’s for myopia

A

VISIAN (PCIOL)
Verisyse (artisan)
ACIOL

106
Q

Advantages of phakic IOL

A 
Larger myopic and hyperopic correction
Skills similar to cataract surgery
Removable
preserves accommodation
Lower risk for RD
107
Q

Disadvantages of phakic IOL

A 
Risks for intraocular surgery
Unintended post op astigmatism
less flexibility in fine-tuning outcome
Explanted during cataract surgery
Less encouraged for hyperopes
108
Q

Contraindications of phakic IOL implantation

A 
compromised endothelium
iritis
significant iris abnormality
rubeosis
cataract
glaucoma
109
Q

Complications of PIOL

A 
glare
haloes
pupil distortion
endothelial cell loss
starbursts
hyphema
IOL dislocation
cataract
110
Q

Range for PIOL

A

-3 to -24 D

+1 to +12 D

111
Q

Bioptics = ____+____

A

PIOL + LASIK

Corneal flap prepared, lens implantation
After 1 month, flap is lifted and refractive surgery is done

112
Q

Removal of crystalline lens even without significant cataracts and replacement with IOLs. Performed if other refractive procedures are not feasible and patient does not want to wear specs/CTL.

A

Refractive lens exchange

113
Q

Range of CLE

A

-30 to +10 D

114
Q

Advantages of CLE

A

Rapid visual rehab
predictability of refractive outcome
retains normal corneal contour
can treat accommodation depending on IOL

115
Q

Disadvantages of CLE

A

loss of accommodation
risks associated with cataract surgery
higher patient expectations

116
Q

Laser related complications of refractive surgery

A

Uneven ablation/central islands
decentered ablation
can cause decrease in BCVA due to irregular astigmatism

117
Q

Flap related complications of refractive surgery

A

intraoperative - buttonhole, irregular flap, free cap, epi defect, corneal perforation, vertical gas breakthrough, AC gas bubbles, limbal bleeding
early post op - flap striae, DLK, interface debris
late post op - flap dislocation, epithelial ingrowth

118
Q

post-operative complications of refractive surgery

A 
displaced flap
flap striae/wrinkling
DLK
epithelial ingrowth
infection
flap melting
119
Q

complications of surface ablation procedures

A

delayed epithelial healing

corneal haze

120
Q

Risk factors for buttonhole

A

steep corneas > 48D
irregular corneal surface
poor blade quality

121
Q

How to prevent buttonholes?

A

Check quality of blade
Use a smaller ring size for steep corneas

(Smaller ring for Steeper cornea)

122
Q

Management of buttonholes

A

postpone laser treatment
align and replace flap properly
recut 3-4 months latter

(hassle!)

123
Q

Risk factors for free cap

A

Free Kap = Flat K

inadequate suction or vacuum

124
Q

How to prevent free cap?

A

Ensure adequate vacuum
Use large ring size for flat corneas

(Large, fLat)

125
Q

Management of free cap?

A

May still proceed with ablation
Just align flap properly
may need BCTL or sutures

126
Q

Risk factors for incomplete/short/irregular flap

A

Blockage of keratome passage
Loss of suction
premature stopping

127
Q

How to prevent incomplete/short/irregular flap?

A

Adequate globe exposure

Ensure good microkeratome perfrmance

128
Q

Management of incomplete/short/irregular flap?

A

Can proceed if with enough space for full ablation, otherwise delay

129
Q

What to do if the cornea is perforated?

A

Deactivate suction
Remove microkeratome
Repair

130
Q

Occurs during femtosecond laser flap creation; Results in escape of gas bubbles from the dissection plane into the subepithelial space. Exact cause unknown but may be related to a thin flap or focal break in BM.

A

Vertical gas breakthrough

131
Q

Management of vertical gas breakthrough

A

Small: lift flap cautiously and perform ablation
Large: Recut or convert to an ablative procedure at later date

132
Q

Occurs when gas bubbles escape from dissection plane into the trabecular meshwork then to the AC. Can interfere with pupillary tracking.

A

AC gas chambers.

133
Q

Management of AC gas bubbles

A

Self-limiting

134
Q

What is DLK?

A

Diffuse lamellar keratitis

135
Q

What is PISK?

A

Pressure induced stromal keratitis

Interface inflammation similar to DLK
appears days to weeks later
associated with elevated IOP

136
Q

What is CTK?

A

Central toxic keratitis

137
Q

most frequent complication after primary LASIK

A

residual refractive error

138
Q

Mechanisms of regression

A

Nuclear sclerosis, stromal synthesis, compensatory epithelial hyperplasia, iatrogenic keratoectasia

139
Q

Management of regression

A

Flap lifting + ablation

Topical steroids with MMC

140
Q

Etiology of glare and haloes in refractive sx patients

A

treatment zone < scotopic zone
large scotopic pupil > 7 mm
decentered ablation

141
Q

How to prevent glare/haloes?

A

Proper treatment zone size

Proper laser alignment

142
Q

Management of glare/haloes

A

Assurance
Miotics
retreat with larger zone

143
Q 
The following result to \_\_\_\_\_\_:
Incorrect flap repositioning
rough flap manipulation
micro-misalignments from ablation
forceful blinking or eye rubbing
A

Flap striae

144
Q

Effects of flap striae

A

Decrease BCVA

High or irregular astigmatism

145
Q

Management of flap striae

A

if peripheral and with good VA, no treatment
if visually significant, relift flap, reposition, iron out wrinkles
BCTL

146
Q

Risk factors for flap dislocation

A 
excessive lid squeezing
eye rubbing
excessive dry eye
presence of epithelial abrasions
poor intraoperative positioning
excessive flap irrigation
trauma
147
Q

DLK is also called ____________.

A

Sands of Sahara

148
Q

What is DLK?

A 
Post-operative interface inflammation
WBC infiltrate between flap and stromal bed
Onset 12h-6 days
Presents with photophobia and reduced VA
starts peripherally
149
Q

Possible mechanisms for stimulating interface keratitis

A 
Betadine
MGD secretions
blade debris
carboxymethylcellulose drops
interface Hgb
bacterial endotoxins
epi defects
150
Q

White, granular cells in periphery

No visual effect

A

Stage 1 DLK

151
Q

Management of Stage 1 DLK

A

Topical steroids

152
Q

White granular cells reaching the visual axis

A

Stage 2 DLK

153
Q

Management of stage 2 DLK

A

intensive topical sterioids

154
Q

Aggregation of clumped cells in the visual axis. Presents with haze and decreased VA.

A

Stage 3 DLK

155
Q

Management of stage 3 DLK

A

Wash flap, intensive topical or oral steroids.

156
Q

Stromal necrosis
Flap melt
r/o infectious keratitis

A

Stage 4 DLK

157
Q

Management of Stage 4 DLK

A

wash flap, intensive topical steroids or oral steroids
GSCS

(take note, you oly do GSCS for stage 4)

158
Q

Management of PISK

A

Hold steroids

159
Q

Chracterized by epithelial migration towards interface. Can lead to stromal necrosis. Occurs due to poor flap adhesion and alignment. RF: buttonhole flaps, epithelial slide or abrasion.

A

Epithelial ingrowth

160
Q

When it is necessary to treat epithelial ingrowth?

A
  • if VA is affected
  • presence of stromal melt
  • progression
161
Q

management of epithelial ingrowth

A

lifting of flap/scraping and removal of epithelial sheet

162
Q

adverse outcomes of delayed epithelial healing

A 
stromal scarring
irregular astigmatism
persistent corneal epithelial defects
recurrent epithelial erosions
epitheliopathy
163
Q

management of delayed epithelial healing

A

d/c BCTL

stop: anesthetics, NSAIDs, epithelial toxic antibiotics, anti-glau meds
give: art. tears and steroids to rpevent scarring

164
Q

most common early and late postop complication post LASIK

A

dry eye

165
Q

When does dry eye post-LASIK usually resolve?

A

After 6 to 9 months

166
Q

usual organisms for Ref Sx related infection

A

bacterial (atypical mycobacteria, nocardia)
viral
fungal

167
Q

management of ref sx related infection

A

lift flap - fulture - wash flap with antibiotics (amik, vanco, moxi) - give topical antibbiotics

168
Q

etiology of corneal ectasia in refractive surgery

A

excessive, deep central ablation

169
Q

Recommended residual corneal thickness for LASIK and PRK

A

LASIK - 250 um

PRK - 350 um

C.EyeMD (8 decks)

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