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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

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LASIK & PRK: Potential Post-op Corneal Opacities

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LASIK & PRK: Potential Post-op Corneal Opacities

Terrence S. Spencer, M.D.

February, 2013


  • financial disclosure:

    • No current financial interest or consulting fees related to any products discussed


  • 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


  • 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

  • Photo-Refractive Keratectomy


  • CK: conductive keratoplasty

  • Phakic IOL’s – VisianStaar 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

  • SvyatoslavFyodorov (Moscow)

    • 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

      • 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 LamellerKeratoplasty (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 Yttrium-Aluminum-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: RangaswamySrinivasin (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


  • 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



  • 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.


  • 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


  • 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 femtosecondlaser

  • 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.

1 Micron

A microplasma is created, vaporizing

approximately 1 micron of corneal tissue

IntraLase Photodisruption

A pulse of laser energy is focused to

a precise spot inside the cornea

2 Microns

IntraLase Photodisruption

An expanding bubble of gas & water is createdseparating 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


Tighter spot placement facilitates easier flap lifts

IntraLase Photodisruptionto 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


  • 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 PunctateKeratitis (SPK)

2)Diffuse Lamellar Keratitis (DLK)

3)Epithelial ingrowth

4)Interface debris

  • 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

    • Arcussenilis

    • 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

    • 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!


    • 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

    • Punctalplugs

      • 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


      • 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.

    Location – in the flap interface


    Tear film debris - in interface- looks oily or has small spots.

    Interface Debris

    Interface Debris

    • Powder-like debris from tissue ablation

      • It can look like DLK or Epithelial cells.

      • Refractileor 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

    • 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

        • Povidone-iodine

        • Distilled water used on surgical instruments

        • Surgical marking pen

        • Microkeratome oil

        • Bacterial endotoxins

        • carboxymethylcellulosedrops,

        • Meibomiangland 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.

    • Can occur with corneal trauma even many years post-LASIK

    • Can occur when we do PRK over an old LASIK flap.


    • 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 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


    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

      • 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

      • Muro128, 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.

    • PredForte 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 striavs folds

    • Can be obvious or very fine (micro-striae)

    • If off visual axis, rarely effects vision

    • Central micro-striaecan 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 ConsiderationsEBMD

    • 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.


    • 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 (fluoresceinstain or no stain)


    • Can it be left alone?

      • Visually insignificant Microstriae

      • Tear film debris in interface

    • Does it need immediate management?

      • DLK

      • Slipped flap

      • Infectious keratitis

      • Aggressive epithelial ingrowth


    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.


    • Questions?


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