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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

LASIK & PRK: Potential Post-op Corneal Opacities

Terrence S. Spencer, M.D.

February, 2013


Disclosures
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
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 anatomy1
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
What is Refractive Surgery

  • Photo-Refractive Keratectomy

  • LASIK

  • 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
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 surgery1
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 surgery2
History of Refractive Surgery

  • Conveyer operating theater in Soviet Union


History of refractive surgery3
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



History of refractive surgery4
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 surgery5
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 surgery6
History of Refractive Surgery

  • Laser: Light Amplification by Stimulated Emission of Radiation

    • 1917: theorized by Albert Einstein

    • 1960: first successful laser


History of refractive surgery7
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 surgery8
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 surgery9
History of Refractive Surgery

  • Photorefractive keratectomy (PRK)

  • 1st eye surgery done with excimer laser

  • 1987 in Berlin: Dr. Theo Seiler


History of refractive surgery10
History of Refractive Surgery

  • 1990: Laser In-Situ Keratomeleusis (LASIK)

    • Epithelium intact = less pain from exposed nerves

    • Combines flap (ALK) with excimer laser (PRK)



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
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
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.



Lasik laser assisted in situ keratomileusis
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
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 basics1
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
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
Concerns with LASIK

  • Microkeratome:

    • Flap creation with a blade is responsible for the majority of the possible procedural complications


What is femtosecond laser
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
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
The IntraLase®laser is a femtosecondlaser

  • How does a laser cut a flap?


Femtosecond laser1
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


Intralase photodisruption
IntralasePhotodisruption

Tighter spot placement facilitates easier flap lifts


Intralase photodisruption to create horizontal cleavage plane
IntraLase Photodisruptionto create horizontal cleavage plane


The planar flap
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)





Intralase
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



Differential diagnosis
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
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 cont1
Differential Diagnosis Cont.

  • Other considerations:

    • Corneal scar – look back at pre-op exam findings

    • Corneal Edema

    • Arcussenilis

    • Loose epithelium


Most common post op findings
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
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
    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
    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 syndrome1
    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
    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 management1
    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

    • 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



    Under the surface
    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


    Interface debris1
    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
    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
    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
    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 dlk1
    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.

    • 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 and intralase flap technology
    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 technology


    DLK technology


    Dlk grade
    DLK technologyGrade

    • 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 grade1
    DLK technologyGrade

    • DLK usually starts within 24 hours, and peaks at about post-op day 5


    Dlk management
    DLK Management technology

    • 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 management1
    DLK Management technology

    • If severe photophobia

      • Cycloplegia

    • ALWAYS REMEMBER TO MONITOR IOP WHILE ON STEROIDS!!!



    Epithelial ingrowth
    Epithelial Ingrowth technology

    • 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.



    Epi ingrowth with mk
    Epi-ingrowth technology with MK

    Epi cells in interface


    Epithelial ingrowth2
    Epithelial Ingrowth technology

    • 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.




    More epitheilial ingrowth
    More technologyEpitheilial Ingrowth


    Assessment of epithelial ingrowth
    Assessment of Epithelial Ingrowth technology

    • 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
    More technologyEpithial Cell Ingrowth


    Management of epithelial ingrowth
    Management of Epithelial Ingrowth technology

    • 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 ingrowth5
    Epithelial Ingrowth technology

    • Less Common with IntraLase

      • Due to inverted bevel-in side cut


    Irregular flap edge
    Irregular flap edge technology

    • 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
    Apical Scar from technologyectasia

    • Corneal ectasia

      • Similar to KCN

      • Very rare under today’s conservative standards for patient selection


    Post operative reticular haze
    Post Operative Reticular Haze technology

    • 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
    Corneal Haze technology


    Additional complications
    Additional technologycomplications

    • 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 stria management
    Flap Stria Management technology

    • 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
    Slipped Flap technology

    • 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 flap1
    Slipped Flap technology


    Button hole flap complication
    Button Hole Flap Complication technology

    • 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
    Less Common technologyConcerns

    • 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
    Less Common Post op Concerns technology

    • 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
    Other Final Considerations technologyEBMD

    • 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
    SUMMARY technology

    • 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)


    Summary1
    SUMMARY technology

    • 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


    Summary2
    SUMMARY technology

    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
    THANK YOU!! technology


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