LASIK & PRK: Potential
Post-op Corneal Opacities
Terrence S. Spencer, M.D.
February, 2013
Disclosures
•
financial disclosure:
–
No current financial interest or consulting fees
related to any products discussed
Purpose
• To educate optometrists
– Familiarize with possible post-operative complications
of LASIK and PRK
– LASIK is a surgery, and all surgery has some risk
Terrence S. Spencer, M.D.
Tunnel on the Peter Norbeck Scenic Byway
Outline
• Briefly Review Corneal anatomy
• Refractive Surgery vs. Corneal refractive
surgery
• History of Refractive Surgery
• Basics of corneal refractive surgery
– PRK and LASIK
• Flap creating technology - Intralase.
• Complications and what to do.
Corneal Anatomy
Corneal Anatomy
• Corneal Transparency:
– Based on highly organized system
• Stroma:
– Layers of fibroblasts between sheets
of lamella.
• Ground substance:
– Maintain proper position of the
fibrils equidistant from each other
• Opacity (or scar):
– Forms when organization of
structure is disrupted
What is Refractive Surgery
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Photo-Refractive Keratectomy
LASIK
CK: conductive keratoplasty
Phakic IOL’s – Visian Staar ICL
Refractive lens exchange or cataract
surgery
– Presbyopia-correcting & Toric IOLs
• Corneal implants
• Intracor procedure
History of Refractive Surgery
• Ancient Chinese:
– Slept with sandbags on eyes to flatten
the cornea
• 1800 -1900’s:
– A variety of devices to modify the
shape of cornea with pressure or
suction
• 1898:
– keratotomy experiment in rabbits.
History of Refractive Surgery
• Svyatoslav Fyodorov (Moscow)
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1939-2000
Early1970s: boy on bicycle (-6 D)
1974: started doing RK on humans
Radial incisions “relax” tension on
peripheral cornea to flatten the
center
– Late 1970s: US surgeons started
performing RK
History of Refractive Surgery
• Conveyer operating theater in Soviet Union
History of Refractive Surgery
• Jose Barraquer
– 1916-1998
– The father of modern refractive
surgery
• Several inventions
– Born in Spain, but moved to
Bogotá, Columbia in 1965
Lathe (for background info only)
History of Refractive Surgery
• Keratomileusis (Jose Barraquer)
– 1949: 1st publication on changing
shape of cornea to change refraction
– Cryolathe
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•
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Layer of cornea removed
Stained and Frozen
Lathed
Sutured back in place
Sutures removed weeks later
History of Refractive Surgery
• Microkeratome: (Barraquer)
– Allowed for in situ correction
• ALK: Automated Lameller
Keratoplasty (Luis Ruis)
– Microkeratome 1st makes an
incomplete flap
– Microkeratome readjusted for the
power cut.
– Never gained great popularity
History of Refractive Surgery
• Laser: Light Amplification by Stimulated
Emission of Radiation
– 1917: theorized by Albert Einstein
– 1960: first successful laser
History of Refractive Surgery
• Laser: Wavelength of light is determined by
the type of gas or solid medium
– Example: YAG laser – crystal of YttriumAluminum-Garnet = 1064 nm
History of Refractive Surgery
• Excimer (Excited Dimer of Argon and Flourine) Laser:
– 1968: Excimer laser invented
– 1970’s: Etching silicone computer chips
– 1982: Rangaswamy Srinivasin (IBM): excimer laser
can ablate tissue without causing heat damage
– 1983: Steven Trokel (NYC) patented excimer laser
use for vision correction
– 193 nm (ultraviolet)
History of Refractive Surgery
• Photorefractive keratectomy (PRK)
– 1st eye surgery done with excimer laser
– 1987 in Berlin: Dr. Theo Seiler
History of Refractive Surgery
• 1990: Laser In-Situ Keratomeleusis (LASIK)
– Epithelium intact = less pain from exposed nerves
– Combines flap (ALK) with excimer laser (PRK)
Procedure Descriptions
PRK
• PhotoRefractive Keratectomy
– First performed in 1987
– Removal of tissue with excimer laser
• Other names for PRK
– LASEK (laser epithelial keratomileusis)
• The epithelium layer is placed back on the stroma
after corrective laser is completed
– Epi-LASIK
• A device called an epikeratome is used to remove
the epithelium
Photorefractive Keratectomy (PRK)
• Step 1:
– Epithelium is removed
• diluted alcohol, brush, vibrating
blade, laser
• Discarded or replaced
• Step 2:
– Excimer laser correction
• sculpting the cornea
• Either flattening or a steepening
pattern +/- astigmatism correction
PRK post-op expectations
• Soft bandage contact lens
– Placed immediately following treatment
– Helps with patient comfort
– Acts as a protective barrier for the healing process
• Epithelium closes in ~ 3-7 days
• Epithelial healing line
– Visible where leading edges of epithelium meet in
center of cornea
– Can induce temporary astigmatism. It can takes
weeks to months to stabilize.
PRK for Athletes
LASIK- laser assisted in-situ keratomileusis
• Laser-Assisted
– The removal of tissue is
done with excimer laser
• In-Situ (latin)
– In place in the body
• Keratomileusis
– Kerato (Greek): cornea
– Mileusis: to shape
LASIK SURGERY BASICS
• TWO STEPS OF LASIK
• 1: Corneal flap
– Microkeratome or Femtosecond laser.
– Layer includes epithelium, Bowman’s
membrane, some anterior stroma.
– The corneal flap is then folded back.
• 2: Excimer laser
– Ablates the corneal stroma to correct the
refractive error.
LASIK SURGERY BASICS
• After excimer laser treatment
– Cornea irrigated with sterile saline
– Examine for any debris
– Irrigate until the interface is clear of any
debris.
• Flap is positioned back into the original
position in the corneal bed
– Smooth out any micro-striae
LASIK
• Immediately after LASIK
surgery:
– Patient’s vision is foggy
– cornea edema may cause difficulty
to see any striae, debris etc.
– Some small particles in the flap
interface are not visible until the
one-day post-op visit.
Concerns with LASIK
• Microkeratome:
– Flap creation with a blade is responsible for the
majority of the possible procedural complications
What is femtosecond laser?
• Femto- is a prefix in the metric system
– Denotes a factor of 10-15 (0.000000000000001)
• Femtosecond = 1 quadrillionth of a second
– Category: ultrashort pulse (ultrafast) laser
Femtosecond laser
• Advantage of ultra-short pulse lasers
– Extremely precise
• Cuts material by ionizing it at the atomic level
– Pulses are too brief to transfer heat to the
material being cut
• No damage to surrounding tissue
– Femtosecond lasers are “cold” lasers
The IntraLase® laser is a
femtosecond laser
• How does a laser cut a flap?
Femtosecond Laser
• Laser pulse is focused to desired corneal depth
• Depth and hinge placement are adjustable based on
individual patient factors
– Corneal thickness, steepness, and/or diameter
• FS laser produces precisely beveled edge architecture
to enable secure flap positioning
– Resists displacement
– Less risk of epithelial ingrowth.
IntraLase Photodisruption
A pulse of laser energy is focused to
a precise spot inside the cornea
1 Micron
A microplasma is created, vaporizing
approximately 1 micron of corneal tissue
IntraLase Photodisruption
2 Microns
An expanding bubble of gas & water is created
separating the corneal lamellae
IntraLase Photodisruption
The bi-products of photodisruption (CO2 & water)
are absorbed by the mechanism of the endothelial
pump, leaving a cleavage plane in the cornea
Intralase Photodisruption
Tighter spot placement facilitates easier flap lifts
IntraLase Photodisruption
to create horizontal cleavage plane
The Planar Flap
• IntraLase provides uniform flap thickness
– Independent of patient keratometry
– Reduction of induced irregular astigmatism
– Optimizes stromal bed for wavefront guided
vision correction
– Increased flap stability (less slipped flaps)
Post-operative flap edge
One day post op
Intralase 1Day post op
Intralase
• Contraindicated in eyes with a corneal scar.
– Laser may not penetrate through the opacity
– May cause a gas bubble breakthrough or a tear
in the flap underneath the scar
Corneal opacities after LASIK
Differential Diagnosis
1)Superficial Punctate Keratitis (SPK)
2)Diffuse Lamellar Keratitis (DLK)
3)Epithelial ingrowth
4)Interface debris
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Tear film –oily deposits
Cloth fiber
Cilia, Eyelash
Sponge particles
Mascara
Etc
Differential Diagnosis Cont.
5)Corneal infiltrate
6)Corneal ulcer
7)Herpetic lesion
8)Epithelial Basement Membrane Dystrophy
(EBMD)
9)Micro striae vs. Slippped flap or folds
10)Prominent corneal nerves
Differential Diagnosis Cont.
• Other considerations:
– Corneal scar – look back at pre-op
exam findings
– Corneal Edema
– Arcus senilis
– Loose epithelium
Most Common Post-op findings
• Dry eye/ SPK or PEK
• Tear film debris interface
– oily or small spots
• Other Interface debris
– sterile fiber, eyelash
• Post operative reticular haze in interface
• Pre-existing Corneal scar
• Corneal scarring at flap edge
Less Common findings
• Diffuse Lamellar Keratitis
– “Sands of the Sahara”
• Epithelial ingrowth
• Infectious infiltrate
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Sterile infiltrate
Infectious Ulcer or infiltrate
Fungal infection (rare)
Peripheral infiltrate, not in flap interface – can be
due to corneal neovascularization
• Herpetic lesion
– Surgical stress may re-activate a dormant
virus
WHERE is the Opacity?
• Biomicroscopy (Slit Lamp) Assessment
– Depth? Look carefully with the optic section
• Surface – Epithelial
– It should stain
• Flap interface
– It won’t Stain
• Stromal
– It won’t stain. Is it anterior, posterior?
• Endothelial
– Endothelial folds from a very edematous cornea.
Unlikely with LASIK. More common with PRK
Dry Eye Syndrome
• The Most Common adverse side effect of
LASIK / PRK
– Exam findings: SPK/PEK
– Can dramatically effect visual acuity.
• If not quickly resolved
– Can lead to poor healing and a “non-perfect”
visual outcome.
• DES can lead to Myopic regression
– Which then requires an enhancement which
could lead to more dry eye!
DRY EYE SYNDROME
• Surface epithelium will stain
– Sodium Fluorescein dye
– Rose Bengal, Lissamine green
• Symptoms:
– Less pain than expected d/t nerve
damage
• Affects visual acuity.
– Like looking through textured glass.
Vision appears grainy, foggy.
Dry Eye Management
• Artificial tears q30min-1hr
– Preservative free
– Consider Celluvisc or ointment
at bedtime
• Punctal plugs
– Temporary collagen
– Permanent - Silicone
• Restasis- one drop BID
Dry Eye Management
• Doxycycline (oral)
– Anti-inflammatory effect as well as improve
proper meibomian gland function.
• Nutritional supplements – Fish Oil & Flax
seed oil 2000mg daily.
• Consider low-potency steroid
– Loteprednol (Lotemax)
– Fluorometholone (FML)
Severe Dry Eye
• Severe Dry eye patients
– If not improving with all of the typical
dry eye management
• Consider BLOOD PLASMA
TEARS
– Autologous
– Contains nutrients, platelets, proteins,
minerals, antibodies, imunoglobulins
Blood Plasma Tears
Under the surface
• If it doesn’t stain, consider that it may be
something in the interface.
Interface Debris
• Location – in the flap
interface
• It WILL NOT STAIN.
– Tear film debris - in
interface- looks oily or has
small spots.
Interface Debris
• Powder-like debris from
tissue ablation
– It can look like DLK or
Epithelial cells.
– Refractile or glistening
appearance.
– Document. It shouldn’t look
different at the next visit.
– If it grows, it may be DLK or
epithelial ingrowth.
Interface Debris Cont.
 Particle/spec:
 If no inflammation and not affecting vision, leave it
alone.
 Flap lift to irrigate can increase risk of epithelial
ingrowth.
 If affecting vision, we lift and irrigate, a.s.a.p.
More Flap Interface Complications
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Diffuse Lamellar Keratitis
Epithelial ingrowth
Post op corneal haze in interface
Slipped flap
Button hole flap
Example: Interface haze d/t
endothelial cell deficiency
Diffuse Lamellar Keratitis (DLK)
• AKA- Sands of the Sahara
• White blood cells in the flap interface.
• Etiology
– Inflammatory response to surgical trauma,
– Reaction to solutions
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Povidone-iodine
Distilled water used on surgical instruments
Surgical marking pen
Microkeratome oil
Bacterial endotoxins
carboxymethylcellulose drops,
Meibomian gland secretions
detergents, contaminated air particulates
– Idiopathic (UNKNOWN cause)
Diffuse Lamellar Keratitis (DLK)
• Increased incidence with
– Atopic, allergic patients
– Blepharitis.
• Pre-treat bleph with oral Doxycycline, lid scrubs, topical
medications before LASIK and PRK.
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Can occur with corneal trauma even many years post-LASIK
Can occur when we do PRK over an old LASIK flap.
DOES NOT OCCUR WITH PRK ALONE (no flap, no DLK)
Can be detected as early as the one day post op visit. Look at
the flap interface very carefully!
• Can look like SPK but DOES NOT STAIN!!
Diffuse Lamellar Keratitis (DLK)
Diffuse Lamellar Keratitis (DLK) and
Intralase flap technology
• Incidence of significant DLK
– 0.1% of LASIK patients with the microkeratome
– Slightly more risk with early model of Intralase
DLK
DLK
DLK Grade
• DLK Classification system
– Stage 1- Faint sterile infiltration of
infammatory cells at the flap edge within
the interface
– Stage 2- More central diffuse pattern
– Stage 3- inflammatory cells within the
visual axis lead to reduced visual acuity
– Stage 4-(rare) Collagenase release and
stromal melting and subsequent loss of
BSCVA.
DLK Grade
• DLK usually starts within 24 hours, and
peaks at about post-op day 5
DLK Management
• Consult back with BHREI
– Grade 1-Manage with Pred Forte 1% q2h and see every
3-5 days
– Grade 2-3 Pred Forte q1-2h. Consider stronger
Durezol. The patient is to be seen every 24 hours until
DLK begins to regress.
– Grade 3-4+ Refer back to BHREI.
• Pred Forte or difluprednate (Durezol)
• May need oral Prednisone
• Flap lifted and irrigated.
DLK Management
• If severe photophobia
– Cycloplegia
• ALWAYS REMEMBER TO
MONITOR IOP WHILE ON
STEROIDS!!!
Epithelial Cell Ingrowth
Epithelial Ingrowth
• Surface epithelial cells in the flap
interface.
• More common with enhancements
than with primary LASIK
• With each additional surgery or
flap lift, the risk increases.
Epithelial Ingrowth
Epi-ingrowth with MK
Epi cells in interface
Epithelial Ingrowth
• Trauma induced by lifting
the flap activates the
epithelial cells
• A disrupted edge may
create a path for
migration of epi cells
– which then multiply and
continue to grow into the
flap interface.
Epithelial Ingrowth
Epithelial Ingrowth
More Epitheilial Ingrowth
Assessment of Epithelial Ingrowth
• Assessment of the cells
– Can have different appearances
• Sheet-like, globular, cystic
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Measure and document at each visit
Is it at the edge or a central island?
Is it progressive or stable?
Is it affecting vision?
Is it creating surrounding tissue scarring or
edge melt?
More Epithial Cell Ingrowth
Management of Epithelial Ingrowth
• If the cells are progressive, abundant, central or
affecting vision
– Send back to BHREI for lift and scrape a.s.a.p.
• If minimal, at the edge and not affecting vision –
MONITOR, but carefully
– If it doesn’t appear aggressive, follow up in 3 weeks.
– If appears aggressive, follow up in 1 week
– Muro 128, 5% may help to seal the flap edge by
compacting the corneal layers. QID.
Epithelial Ingrowth
• Less Common with IntraLase
– Due to inverted bevel-in side cut
Irregular flap edge
• Epithelial cells in flap edge can have a
toxic by-product.
• Ingrowth can cause scarring and even
lead to corneal melt.
• Pred Forte may be applied if the flap
edge is becoming irregular. PF Q2h
follow every 5-7 days to monitor for
increasing melt.
• Scar will not go away, even with
treatment. Just try to control more
damage.
Apical Scar from ectasia
• Corneal ectasia
– Similar to KCN
– Very rare under today’s
conservative standards
for patient selection
Post Operative Reticular Haze
 Late onset
 6 wks to 6 mo post op
 Can affect both PRK and
LASIK patients
• Can reduce visual acuity
• If caught early-on, treat with
Pred Forte q1-2h then qid.
Takes weeks to months to
clear. If longer term therapy
(more than a month) switch
to FML or Alrex.
• Don’t forget to monitor
IOP!!
Corneal Haze
Additional complications
• Flap stria vs folds
• Can be obvious or very fine
(micro-striae)
• If off visual axis, rarely effects
vision
• Central micro-striae can
effects visual acuity, but often
does not.
Flap Striae Vs Folds
Flap Stria Management
• If affecting vision
– Send back to the surgeon for lift and smooth a.s.a.p.
– Each additional lift increases risk of epi ingrowth
• If off visual axis, not affecting vision, and the
flap edge/gutter is not exposed, can often leave
it alone.
• Early post op
– A Q-tip stretch technique can smooth out the small
peripheral wrinkles without having to do a lift.
Slipped Flap
• Requires a surgical
intervention (lift and stretch)
ASAP
• Wrinkles don’t always fully
resolve
• May have long term visual
affects
• May have normal visual
outcome with proper
treatment
• Over time, vision can improve
even with some residual stria
post lift.
Slipped Flap
Button Hole Flap Complication
• Manage it like PRK
• Wait for corneal surface
to heal and refraction to
stabilize.
• PRK once fully healed.
• Usually patients do well,
may have a central scar
with decreased BCVA.
Less Common Concerns
• Corneal Infiltrates
– Treat with Pred Forte and
Zymar or Combo drop
(TobraDex)
– monitor closely.
• Infectious Ulcers
– Treat aggressively
(Fluoroquinolone or fortified
antibiotics) and monitor
daily.
– May leave a scar
Less Common Post op Concerns
• Surgical trauma
– can stress the corneal nerves and lead to a
re-activation of corneal HSV.
• HSK. Usually is contraindication for
LASIK surgery.
• If you see this post LASIK, start
antiviral therapy immediately
Other Final Considerations
EBMD
• EBMD- maps can look like
striae.
• Post op LASIK -If the epithelium
is loose it can slough and create
discomfort, slow the healing.
• If they have dry eye, can cause
painful recurrent corneal
erosions.
• Important to look closely pre-op
to identify EBMD and consider
PRK instead.
SUMMARY
• Very careful exam on the 1-day and 1-week
post op.
• If there is an opacity, consider the following:
– What is it?
– Where is it?
• Surface vs interface (fluorescein stain or no stain)
SUMMARY
• Can it be left alone?
– Visually insignificant Microstriae
– Tear film debris in interface
• Does it need immediate management?
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DLK
Slipped flap
Infectious keratitis
Aggressive epithelial ingrowth
SUMMARY
When in doubt, send it out
• BHREI is more than happy to see a patient
for an evaluation, please send them back to
us if you have any concerns.
THANK YOU!!
• Questions?
• tspencer@bhrei.com