Complications in refractive surgery

1
Complications in refractive surgery

• Modified by Corina van de Pol, O.D., Ph.D.
• July 28, 2001
• James Colgain, OD
• Mitch Brown, OD, FAAO

2
Complications of PRK

• healing
• Epithelial compromise
• Corneal infection
• Corneal haze
• Corneal scar
• infection - rare 15,000

• refractive
• over/undercorrection
• Regression
• Central Islands
• laser
• Decentered ablation

3
Over/under-correction

• Cause
• inaccurate refraction
• unstable
• CTL warpage especially in HCL or GPHCL
• undetected pathology (KCN)
• unpredictable healing
• induced cylinder
• occult autoimmune disorder

4
Over/under-correction

• Treatment
• based on refractive stability
• change no greater than 0.5D over 1 month
• wait longer in higher myopes and hyperopes
• most surgeons wait at least 3 months
• ok to treat interim over-correction with SCL
• UCVA gt20/40
• based on expectations, patient desire

5
Regression

• lt0.25D myopic regression over 1 year
• US Navy study (n100)
• Retreatment possible
• based on refractive stability and visual
  symptoms/complaints

6
Central islands

• Cause
• plume/debris
• water
• Rare in Lasik, rarer still with scanning lasers
• Not as prevalent with newer software and scanning
  lasers

7
Central islands

• Treatment
• observe
• gt90 of islands resolve spontaneously
• customized ablation
• based on height and diameter of island

8
Epithelial compromise

• Cause
• underlying basement dystrophy
• prior trauma
• dry eye
• smoking

9
Epithelial compromise

• Treatment
• patient selection
• copious tears
• consider punctal occlusion
• bandage CTL
• proper fit
• Acuvue 8.8 for Klt40
• Acuvue 8.4 for Kgt40
• topical antibiotic until epithelium healed

10
Corneal infection

• Rare (lt15,000)
• Worked up and treated like CTL-related microbial
  keratitis
• if lt2 mm, mid-periphery to limbus, consider
  empiric therapy with fluoroquinolone
• if gt2 mm and/or central/paracentral, consider
  scraping for culture and sensitivity and
  aggressive topical fortified antibiotics
  (cefazolin and tobramycin)

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Corneal haze

• Cause
• unclear
• ? UV exposure
• ? Over-exuberant healing response

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Corneal haze

• Treatment
• unclear
• based on vision and refraction
• probably no treatment required if not visually
  significant
• if K's are steepening and refraction shifting
  toward myopia, consider trial of FML
• gt95 of haze clears eventually

13
Corneal scar

• Unresolved haze, refractory to FML
• Potential for vision loss
• Consider PF
• Consider corneal scraping
• Consider mitomycin-C or thio-tepa

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Complications of LASIK

• refractive
• over/undercorrection
• induced astigmatism
• central islands - rare
• laser
• decentered
• less with tracking
• more with longer ablations
• angle kappa and visual axis?

• flap
• buttonhole in pupil
• free cap if small
• epithelial defects especially with older patients
  and dry eyes
• wrinkles, striae
• decentration
• inflammation (DLK)
• epithelial ingrowth (primary and secondary)
• infection - rare 15,000

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Buttonhole

• Cause
• steep K (gt46), greater risk
• cornea "buckles" during microkeratome pass,
  creating central area where blade exits cornea
  then re-enters. This is often in the visual axis
  and is disastrous to vision if the ablation
  occurs.
• May re-cut deeper in cornea in 3-6 months

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Buttonhole

• Treatment
• do NOT perform laser ablation
• irregular astigmatism WILL be induced
• replace flap or dont lift at all
• allow cornea to heal (at least 3 months)
• re-cut thicker flap and decenter entry of the MK
  so as not to disturb initial plane

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Free cap

• Cause
• flat K (lt40D) these are at greater risk
• microkeratome travels completely across flap
• no hinge created
• ALK used to be performed in this fashion
• Surgeon MAY proceed if he bed, cap and area for
  ablation are normal
• Always necessary to mark cornea so the epi side
  is placed up when repositioned

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Free cap

• Treatment
• save free cap in antidessication chamber
• complete laser ablation
• replace cap, aligning with preplaced marks,
  epithelium UP
• consider suture (usually not required) and
  bandage CTL

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Epithelial defects

• Cause
• pre-existing condition
• ABM dystrophy
• recurrent erosion
• prior trauma
• dry eye
• greater suction and torquing motion
• dry surface during microkeratome pass

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Epithelial defects

• Treatment
• patient selection
• pre-existing epithelial conditions listed above
  are relative contraindications to LASIK.
• Consider surface PRK for above conditions
• copious irrigation during procedure
• wet cornea just prior to keratome pass
• bandage CTL
• intraoperative defects may end up being areas of
  RCE during healing phase

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Flap striae

• May result in irregular astigmatism and lost BCVA
• Cause
• technique
• flap laid back with poor attention to detail
• not smoothed properly
• more significant in higher myopes
• patient
• rubbed eye/flap during day one to week one
• possible to dehisce flap completely in first
  24-48 hours

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Flap Striae at 6 weeks post-op
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Flap striae

• Treatment
• technique
• meticulous attention to smoothing flap at time of
  ablation and positioning with attention to
  gutter and pre-op marker alignment
• consider "pressing" flap
• consider refloating flap if visually significant
• rarely, suturing required to stretch flap
• patient
• clear shield at night for first week
• caution patient not to rub eye
• use tears for irritation

25
Flap de-centration

• Cause
• eye torques when suction applied
• may result in decentered ablation
• the larger the ablation zone - especially in
  hyperopes the more significant this issue
• prior to treatment, the surgeon may view the area
  of ablation on most lasers to determine whether
  the bed area is OK for the treatment

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Flap de-centered nasally 1.5mm
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Flap decentration

• Treatment
• if ablation can be performed without hitting flap
  edge, consider proceeding
• if ablation cannot be accomplished without
  hitting flap edge, abort laser, replace flap,
  allow cornea to heal (at least 3 months) and
  recut deeper, centered flap possibly using a
  different MK

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Inflammation

• Received the most press as potential complication
  following LASIK
• Called many names
• Diffuse lamellar keratitis (DLK)
• Sands of the Sahara syndrome (SOS)
• May occur in groups or outbreaks
• Causes (many potential, none proven)
• metallic debris, meibomian secretions, staph
  toxin, keratome oil, infection

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Early DLK _at_ 1 day P/O
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DLK _at_ 6 weeks P/O
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Inflammation

• Treatment (stage-dependent)
• stage I increased frequency of FML
• stage II switch to Pred Forte
• stage III lift flap, irrigate and add Pred Forte
• stage IV stage III Rx and pray
• vision loss probable

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Epithelial ingrowth

• Causes (2 types)
• nests of cells deposited under flap during
  procedure
• migration of epithelium at flap edge

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Epithelial cells under flap
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Epithelial ingrowth

• Treatment
• observe for progression
• if progressive, lift flap, scrape with Weckcell,
  irrigate well and reposition flap
• may require lifting flap more than once
• risk of epithelial ingrowth increases each time
  flap is lifted
• More risk with older patients and poorer
  epithelium
• follow up, early detection and treatment critical
  to the best outcome

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Infection (lamellar keratitis)

• Potentially the most devastating complication
  associated with LASIK
• Fortunately, a rare complication (lt15,000)
• Causes
• poor Betadine prep
• poor lid/lash drape
• bad luck
• post op introduction of infectious agent

36
Infection

• Treatment
• consider lifting flap to scrape for culture and
  sensitivity
• consider aggressive topical fortified antibiotics
  (cefazolin and tobramycin)

37
Flap Dislodgment after Lasik

• Rare no real studies just reported events
• No one knows when the flap heals
• Able to lift some patients 3 years out
• Events leading to flap dislodgment or striae from
  trauma after 30 days
• Airbag, cat and dog scratch, cardboard box edge,
  fingernail scratch during fight, retinal buckle
  surgery, tree branch hitting cornea, snowball hit
  eye

38
PRK

• Advantages
• safer
• longer track record
• costs less

• Disadvantages
• slower recovery
• more discomfort
• corneal haze
• limited range

39
LASIK

• Advantages
• faster recovery
• less discomfort
• less follow-up
• enhancements easier
• high myopia

• Disadvantages
• increased risk
• late flap displacement
• increased cost

40
PRK vs. LASIK Same destination Different
journey

• PRK
• Day one Oowww!
• Less surgical risk
• Slower recovery
• 80 20/20
• Haze
• No flap
• 0.2 0.3 risk visual loss (gt2 lines)

• LASIK
• Day one Wow!
• Greater surgical risk
• Quicker recovery
• 80 20/20
• No haze
• Flap
• 0.2 0.3 risk visual loss (gt2 lines)