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OD3 (S1&2) > DIS - Corneal Refractive Surgery Workup - Week 2 > Flashcards

DIS - Corneal Refractive Surgery Workup - Week 2 Flashcards

1
Q

List 5 types of refractive surgery.

A

Laser in-situ keratomileusis
-LASIK - most common
Photo-refracrive keratectomy
-PRK
Laser assisted sub-epithelial keratectomy
-LASEK
Phakic IOLs
-implantable contact lenses
Refractive lens exchange

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2
Q

List 8 common reasons for having refractive surgery.

A

Convenience
Cosmesis
Increased security
Lifestyle choice
Vision entry requirement
Sport/hobby
Intolerance/poor comfort with contact lenses
Cumulative cost saving

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3
Q

Which refractive surgery is the most common and what percentage does it account for?

A

LASIK - 95%

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4
Q

Briefly describe the procedure for LASIK (3).

A

A thin flap is created in the anterior cornea (epithelium, bowmans layer, anterior stroma)
When folded back, it exposes the central stroma
An excimer laser is used to permanently remove corneal tissue
The flap is replaced

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5
Q

What was the first method used to create a flap in LASIK? What is the flap thickness (range)?

A

Microkeratome
Flap thickness of 100 - 160um

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6
Q

List two potential complications of using a microkeratome.

A

Partial flaps
Free caps

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7
Q

What is an alternative to using a microkeratome? Describe the flap in comparison, its thickness and what two additional things you would expect using this method.

A

Femtosecond laser
Uniform, thin, planar flap
Consistent thickness
Less suction
Flap oedema
Transient light sensitivity

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8
Q

Compare the two methods of flap creation for LASIK in terms of complication rates and visual outcomes.

A

Both have low complication rates and good visual outcomes

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9
Q

What is the theoretical range for LASIK (myopia, hyperopia, and astigmatism)?

A

+4.00 to -8.00DS
Up to -5.00DC
-regular astigmatism

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10
Q

What is an ideal age for LASIK?

A

> 21

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11
Q

List 7 aspects of clinical history that should be taken.

A

Occupation
Hobbies/sporting activities
POH
FH
GH
Allergies
Monovision discussion (trial if appropriate)

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12
Q

List 7 specific aspects of POH to ask a LASIK candidate.

A

Injury
Infection
Surgery
Laser surgery
Amblyopia
Strabismus
Current correction, including CL history

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13
Q

List 4 specific aspects of FH to ask a LASIK candidate.

A

Glaucoma
Diabetes
Myopia
Retinal health

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14
Q

List 3 specific aspects of GH to ask a LASIK candidate.

A

Medications
Systemic conditions
Surgical history

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15
Q

List 12 components of a clinical work-up for a potential LASIK candidate.

A

Ocular dominance
Uncorrected vision
Cover test / phoria
Habitual correction (D/N)
Subjective refraction - dry (D/N)
Pupil size (bright/dim)
Corneal topography
Slit lamp assessment
-tear film assessment
IOP
Pachymetry
DFE
Cycloplegic refraction

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16
Q

What is the expectation with contact lens wear (soft and rigid) prior to doing corneal topography on a LASIK candidate? What three things should you check for on topography and what should you do?

A

No SCL wear for a minimum of 1 week or 4 weeks for RGP
Check for irregularity, asymmetry, and ectasia
Predict post-operative K readings

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17
Q

What should you be weary of with topography on a LASIK candidate and why? What may result if LASIK is done on hyperopic eyes with >49D K readings and myopic eyes <36D?

A

Be weary of extremely flat or steep corneas
<36D - may result in poor post-operative optics
>49D - may result in more dry eye symptoms

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18
Q

What three things should you do during a tear film assessment for a LASIK candidate?

A

NaFl + LG staining
Schirmer test without anaesthesia

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19
Q

What three things should you check for when doing slit lamp examination on a LASIK candidate?

A

Blepharitis
Meibomianitis
Corneal scarring/dystrophies

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20
Q

What is the required post-operative CCT? What three things does ablation depth depend on and approximately how many microns per dioptre?

A

≥410um
Ablation depth based on optic zone diameter, blend zone, and refractive error
-15um per D

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21
Q

What three things should you rule out when doing DFE on a LASIK candidate?

A

Retinal thinning
Holes
Partial detachment

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22
Q

What is the purpose of cycloplegic refraction on a LASIK candidate?

A

Ensure theyre not overminused

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23
Q

List 6 absolute ocular contraindications to LASIK.

A

Refractive instability
-more than 0.5D over 12 months
Corneal ectasia (any form) or irregular topography
Significant corneal scarring
Relatively thin corneas
-baseline thickness <500um
Active corneal pathology
Monocularity

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24
Q

List 5 absolute systemic contraindications to LASIK.

A

Pregnant/nursing women
Autoimmune disease and immunodeficiency
Collagen vascular disorder
Certain medications
Unrealistic patient expectations

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25
Q

List 2 medications that are an absolute contraindication to LASIK.

A

Isotretinoin
Amiodarone

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26
Q

List 3 relative systemic contraindications to LASIK.

A

Oral corticosteroid use
Hormone replacement therapy
Diabetes

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27
Q

List a relative general health contraindication to LASIK.

A

History of keloid scarring

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28
Q

List 2 relative prior ocular history contraindications to LASIK.

A

Herpes simplex
Herpes zoster

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29
Q

List 7 relative ocular health contraindications to LASIK.

A

Severe dry eye
Severe atopy
Severe eyelid disease
Corneal neovascularisa7on
Recurrent corneal erosions
Glaucoma
Large pupil size

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30
Q

List 3 relative occupation contraindications to LASIK.

A

Armed forces
Fighter pilots
Railways

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31
Q

Are contact sports considered a LASIK contraindication?

A

Yes, a relative one

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32
Q

What is the typical optom (4) and ophthal (1) follow-up schedule for LASIK post-operative evaluation?

A

Ophthal - day 1
Optom - week 1, month 1, month 3, month 6

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33
Q

What is the post-operative treatment for LASIK, including dosage and duration (3)?

A

Ciprofloxacin + pred forte qid
-7 days
Regular non-preserved lubrication
-q1h for 48h
-q2h for 1m
-qid for first 3/12

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34
Q

What instructions are patients given post-operatively for LASIK and what may they be given?

A

Not to rub eyes
Protective eye shield overnight
-7 days

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35
Q

What are three normal symptoms of LASIK on the day of surgery?

A

Mild foreign body sensation
Mild ocular discomfort
Hazy vision

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36
Q

What three things should you do a day after LASIK surgery?

A

History
UCVA
Slit lamp

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37
Q

What four things should you do a week after LASIK surgery?

A

History
UCVA
BCVA
Slit lamp

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38
Q

What may be occurring in patients with patients not correcting to 6/6 or pre-op BCVA at one week post-LASIK?

A

Flap or interface complications

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39
Q

What two things should you especially look out for when doing slit-lamp a week after LASIK?

A

DLK
Early epithelial ingrowth

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40
Q

What five things should you do a month after LASIK surgery?

A

History
UCVA
BCVA
Slit lamp
Tonometry

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41
Q

What can be expected of Rx during the first month post-LASIK and why?

A

Slight over-correction of Rx not unexpected
-due to calcaulated nomograms that anticipate a natural regression effect

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42
Q

What may be expected of astigmatism a month after LASIK and why?

A

Mild induced astigmatism due to corneal remoulding or tear film disruption

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43
Q

What six things should you do three months after LASIK surgery?

A

History
UCVA
BCVA
Slit lamp
Topography
Tonometry

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44
Q

What is expected of refraction and VA in patients 3 months after LASIK?

A

Most will have stable refraction and VA

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45
Q

What is the predicted time course for the following:
Halos and glare at night
Fluctuations in vision
Dry eye

A

Halos and glare at night - 4-6 weeks
Fluctuations in vision - 4-6 weeks, up to 3 months
Dry eye - 3-9 months

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46
Q

What is the proportion of intra-operative complications vs post-operative for LASIK (percentage)?

A

Intra-operative - 95%
Post-operative - 5%

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47
Q

What is the incidence of intra-operative complications for LASIK?

A

0.16 to 0.32%

48
Q

List 3 types of intra-operative complications that can occur during LASIK.

A

Microkeratome induced
Laser induced
Epithelial defects

49
Q

List 7 types of post-operative complications that can occur after LASIK.

A

Striae
DLK
Infection
Epithelial ingrowth
Posterior segment (very rare)
Residual refractive error
Corneal ectasia

50
Q

List 5 microkeratome-induced complications that can occur during LASIK.

A

Button-hole
Incomplete/short flap
Free cap
Variable thickness/irregular cut
Contamination of interface

51
Q

In what corneal K readings are button-holes and free caps more common?

A

Button-hole - >48D
Free cap - <41D

52
Q

Are femto-second created flaps more or less accurate vs microkeratomes?

A

More accurate

53
Q

Describe transient light sensitivity sydrome.

A

Ccute light sensitivity, 2-4 weeks post-surgery in the absence of visual or slit lamp signs
Occurs with femtosecond created flaps

54
Q

What 5 things may epithelial defects be due to (intra-operative complication)?

A

Manipulation of the cornea during the procedure
Overuse of topical anaesthetic
Presence of pre-existing epithelial instability
Older age
Diabetes

55
Q

How should epithelial defects be treated (3)?

A

Like a corneal abrasion
-bandage CL overnight
-antibiotic coverage
-regular lubrication

56
Q

What do epithelial defects increase the risk of (2)?

A

DLK
Epithelial ingrowth

57
Q

What are flap striae frequently caused by and in what type of eyes?

A

Eye rubbing/squeezing
-also poor flap placement
More common in myopic eyes

58
Q

Do flap striae affect vision?

A

If central, yes

59
Q

List three treatment options for flap striae.

A

Lift and smooth flap technique
Hypotonic saline
Suture flap

60
Q

What is another name for diffuse lamellar keratitis?

A

Sands of Sahara

61
Q

When does DLK appear?

A

During the first week

62
Q

What is diffuse lamellar keratitis?

A

Inflammatory condititon located at the stromal interface

63
Q

Is DLK uni- or bilateral?

A

Either

64
Q

Does DLK have symptoms?

A

No

65
Q

Is the anterior chamber generally quiet with DLK?

A

Yes

66
Q

What causes DLK?

A

Accumulation of white blood cells pushing up on flap, typically at the edge of the flap
-eosinophils, neutrophils, lymphocytes

67
Q

What can severe cases of DLK result in?

A

Stromal necrosis leading to flap melt and potential corneal scarring

68
Q

What is the aetiology of DLK?

A

Unknown
Probably multi-factorial
-inflammatory response to foreign antigen
-Toxic response to dead Pseudomonas cell wall protein found in
instruments and auto-clave

69
Q

What is the treatment for DLK? What may severe cases require and what should be monitored?

A

1% pred forte q1h
Monitor daily
Taper steroids over 3-4 weeks
Severe cases may require irrigation with steroid
Monitor IOP

70
Q

What is epithelial ingrowth?

A

Epithelial surface cells grow into the flap interface

71
Q

When do epithelial ingrowths occur? Can they occur after 4 weeks?

A

Occurs 1-4 weeks post-op
-will not develop after 4 weeks

72
Q

What can epithelial ingrowth result in if significant?

A

Cap melt within 1-4 weeks

73
Q

List 5 symptoms of epithelial ingrowths. Are they common?

A

Often asymptomatic
Glare
Photophobia
Tearing
Mild ocular discomfort
Visual distortion (if central)

74
Q

What five things are epithelial ingrowths associated with?

A

Epithelial defects
Irregular flaps
Previos corneal surgery
Anterior basement membrane disease
Flap lifts

75
Q

Why can corneal melt occur with epithelial ingrowth?

A

Due to collagenases released by dying, trapped epithelial cells

76
Q

List four symptoms of infectious keratitis. Is it common or rare?

A

Pain
Epiphora
Photophobia
Reduced VA
Rare

77
Q

When can infectious keratitis occur post-LASIK?

A

Any point during the recovery period

78
Q

What can infectious keratitis initially appear similar to?

A

DLK

79
Q

What are the two most common causes of infectious keratitis?

A

Gram + bacteria
Mycobacterium

80
Q

What two things may be required for infectious keratitis?

A

Intensive broad spectrum antibiotics initially
May require flap lift with scraping and irrigation with antibiotics

81
Q

List 5 contributors to dry eye post-LASIK.

A

Neurotrophic disease
Tear film instability
True aqueous deficiency
Local inflammation
Corneal exposure

82
Q

When does dry eye peak post-LASIK?

A

A month after surgery

83
Q

What is a major risk factor for post-op dry eye? List 2 more.

A

Pre-existing dry eye
Deeper ablations
Thicker flaps

84
Q

List 4 posterior segment complications that may occur post-LASIK. Is there a direct cause?

A

Retinal detachment
Choroidal neovascularisation
Macular hole
Macular haemorrhage
No conclusive evidence of LASIK being the direct cause

85
Q

When can post-LASIK ectasia occur? Is it common or rare?

A

May occur at any time after surgery
Relatively rare

86
Q

List four potential risk factors for post-LASIK ectasia, with the most significant one first.

A

Abnormal pre-operative topographic indices
Younger age (<30)
Higher myopia (>8.00D)
Thinner pre-operative corneal thickness

87
Q

What is the management for post-LASIK ectasia?

A

Similar to keratoconus

88
Q

Briefly describe PRK.

A

Debridement of the corneal epithelium, followed by application of the excimer laser onto the stromal surface

89
Q

Briefly describe LASEK.

A

Epithelium is retained, however an alcoholic solution is used to weaken the epithelial cells so they can be folded out of the way

90
Q

List three indications for PRK and LASEK.

A

Mild/moderate Rx with thin cornea
-where there is concern about post-operative ectasia
Recurrent erosions/epithelial basement disease
Predisposition to trauma (martial arts, military)

91
Q

Between PRK and LASIK, which has decreased overall inflammation and faster visual rehabilitation?

A

LASIK

92
Q

What does the creation of a corneal flap induce in LASIK?

A

Physical weakening to the cornea (permanent)

93
Q

Between LASIK and PRK, which has less overall rates of dry eye?

A

PRK

94
Q

What are the visual outcomes like between LASIK and PRK?

A

Comparable outcomes for myopia and hyperopia at one year post-surgery

95
Q

What is the post-operative care for LASEK and PRK (8)? Give duration and dose if appropriate.

A

Bandage CL 1 week
Topical corticosteroids qid
Topical antibiotic qid
Acular bid (day of surgery and day 1)
Non-preserved lubricants q1h
Topical antibiotic 2 days after bandage CL removal
Topical steroids tapered very gradually (12 weeks)
IOP needs to be monitored

96
Q

What is UCVA like over time with PRK and LASEK?

A

Initially very good for the first 2 days, then may drop off as surface abrasion heals

97
Q

What may you see initially on the patients epithelium in PRK and LASEK? Does it affect vision?

A

Epithelium will have an oedematous line at junction point of re-epithelialisation which may further blur patients VA for 2-3 days

98
Q

What are phakic IOLs?

A

Surgically implanted contact lenses

99
Q

Where are phakic IOLs positioned?

A

On or behind the iris and in front of the lens

100
Q

What level of ametropia (and type) is an indication for phakic IOLs.

A

High myopia
-5.00D to -20.00D

101
Q

List four qualities of a good candidate for phakic IOLs.

A

Pre-presbyopic high myope
Deep anterior chamber
Adequate endothelial cell count
No cataract

102
Q

When are phakic IOLs considered?

A

When LASIK/PRK/LASEK re contraindicated

103
Q

Do phakic IOLs induce higher order aberrations?

A

No

104
Q

Is there a risk of corneal ectasia with phakic IOLs?

A

No

105
Q

What provides better vision for high myopes, laser surgery or phakic IOLs?

A

Phakic IOLs

106
Q

What are the risks of phakic IOLs similar to? List them (8).

A

Cataract surgery
-IOP rise
-endophthalmitis
-CMO
-hypopyon
-hyphaema
-corneal oedema
-retinal detachment
-cataract

107
Q

What is the post-op care of phakic IOL surgery similar to? What is required annually (at least)?

A

Cataract surgery
-at least annual specular microscopy of the corneal endothelium

108
Q

What endothelial cell count is a contraindication for phakic IOLs?

A

<2000mm2

109
Q

What is refractive lens exchange?

A

Removal of the crystalline lens for refractive
purposes

110
Q

What does refractive lens exchange eliminate the need for?

A

Future cataract surgery

111
Q

List two indications for refractive lens exchange.

A

Moderate to high myopia
Hyperopia

112
Q

Is refractive lens exchange often considered for patients under 50?

A

No

113
Q

What does refractive lens exchange carry and increased risk of and in what type of eyes?

A

Retinal detachment, especially in young, high myopic eyes

114
Q

List 5 qualities of a good candidate for refractive lens removal.

A

Incipient cataract
Significant refractive error
Presbyopia
Strong desire for reduced dependence on spectacles/CLs
Need to lower IOP

115
Q

What two types of refractive error would make for a good candidate for refractive lens exchange.

A

Significant hyperopia with low astigmatism

OD3 (S1&2) (114 decks)

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