LASIK: COMPLICATIONS AND THEIR MANAGEMENT

Dr. Rujuta GoreDr. Rujuta Gore

Dr. Mrudula BhaveDr. Mrudula Bhave

LASIK: Possible complications

IntraoperativeMicrokeratome relatedFlap related

Early postoperativeLate postoperativeRefractive complications

Intraoperative complications

Inadequate exposure

Inadequate suction

Incomplete Cut

A lamellar cut that does not reach the limit scheduled by the operating program

Causes:Loss of suctionBlock of keratome by drape or dust in its gearsPower failure

Prevention:Precise preoperative check of the instrumentationAdequate exposureContinuous power supply

Mx Incomplete Cut

Unexpected stop- reverse the run direction, remove the suction ring

Complete block- suspend the suction, gently remove microkeratome and suction ring in a direction away from hinge

Sufficient room for refractive ablation- proceedIf insufficient- replace the flap; postpone by 3-6

months

Thin/ Perforated cut (buttonhole)Mechanical Causes:

Inadequate suction Incorrect ring sizePoor blade quality Excessively dry corneaLoose epitheliumEdematous epithelium

Anatomical causes:Very steep corneasIrregular astigmatism

Results:Inability to perform laser ablationRisk of epithelial ingrowth in interface and

possible melting Risk of irregular astigmatism

Mx Thin Cut

Prevention:Avoid excessive use of anaesthetic eyedrops that

may weaken the epitheliumChange the blade after every cut

If flap can be raised, ablation can be performed, paying attention to alignment, avoiding folds while repositioning

Mx Thin Cut

Management:Minimal manipulationReplace the thin flap or buttonholed flap while

carefully managing the epithelial edgeInspect the flap and verify adherenceWash the interface carefullyTherapeutic contact lens

Flap cut around 360° (Free Cap)

Etiology-Large (>14.5mm) , flat cornea

(<41.0D)Poor assembly of

microkeratomeInadequate suctionRemoval of suction ring with

cap still adhered to itReduced intra op IOP

Prevention:Corneal marking for proper

alignment

Mx Free Cap

Keep the flap in antidessication chamber, epithelial side down

Proceed with ablationStromal surface should not be hydratedAlign flap with preop markingsSutures not requiredOR Flap may be discarded; apply a contact lens

to aid epithelial regrowth

Early Postoperative Complications

Flap related complications

Causes:Excessive dehydration due to prolonged surgical timeManipulation with forceps, swabs and other instruments not

suitable for LASIK

Prevention:Alleviate anxietyFlap must not be allowed to dryTime between lifting and reposition minimumAvoid excessive interface irrigationSpeculum removal-gentleProtect the hinge when OZ is large

Flap Complications

Displacement of flapWrinkled flap (micro and macrostriations)Interface debrisFlap edemaFlap shrinkageFlap stretchingDecentration

Displacement of flap

Causes:Incomplete adhesion to

stromaSqueezing of eyes while

drape and speculum removalExcessive movements of eye/

rubbingDryness of eyeAccidental trauma while

instilling drops

Mx:Immediate refloating of flap

into position

Wrinkled flap

Causes:RubbingInstilling eyedropsIncorrect flap

positioningExtremely thin flapDehydration of stromal

surface due to prolonged exposure

Rough handling of flapUse of vasoconstricting

agents like phenylephrine or brimonidine to minimize SCH

Striations: What are they?

Microstriations: folds in Bowman’s membrane. Cause minimal visual deficit

Macrostriations: folds in the flap. Reduce VA due to irregular astigmatism, halos, starbursts

Mx Striations

Micro- can be observedMacro- Flap should be lifted again, interface

should be washed and flap replacedFlap should be smoothed with a Merocel soaked in BSS, perpendicular to orientation of striationsContact lens may be applied

Striations: consequences and Mx

Striae become permanent as epithelium fills the spaces in the folds

MxSoak the epithelial surface by instilling distilled

water. This creates edema and loosens the cells for removal

Remove the epithelium with a spatulaThen raise the flap and irrigate the interface with

BSS, and distilled waterRepositionApply contact lens

Persistent striations

May apply continuous 10-0 Nylon suture to mechanically smoothen the flap

PTK to remove epithelium between striaePTK (10μm) on stromal surface of flap

Interface debris

Causes:Debris from cannula, syringe, microkeratome,

spongeMx:

Inspect the interface and flap before removing drape and speculum

Edge irrigation Lift flap and reposition after irrigation

Microbial Keratitis

Rare but potentially devastating complicationIncidence: 1:5000(0.02% to 1%)Common organisms:

Staph aureus (early onset infections)Mycobacterium chelonae (late onset infections)Candida, Fusarium (later onset)

Predisposing factors:

Poor steririlizationPoor compliance to postop instructionsPoor hygiene

Symptoms:Increased light sensitivity PainRedness Foreign body sensationDecreased vision

Microbial Keratitis

Clinical signs:Corneal infiltrate

Epithelial ingrowth

Epithelial defects

AC reaction

Hypopyon

Microbial Keratitis

Laboratory tests:Scrapings: from stromal bedSmearsCulture

Management:In case of interface infiltrate, lifting of flap and

removal of all infective fociIrrigation with 50mg/mL vancomycin or 35mg/mL

amikacinIntensive fortified antibiotic and antifungal therapy

as per the lab results

Mx Microbial Keratitis

In cases of resistant bacterial infection, flap removal and intensive medical therapy has been found useful

In cases of resistant fungal infection, an aggressive approach consisting of amputation of the flap, daily debridemant of the bed, intensive topical and systemic antifungals may be required

Eyes not responding to medical therapy and those presenting late with large infiltrates may need ALK or TPK

Mx Microbial Keratitis

Prevention:Treatment of blepharitis preoperativelySterile techniqueCareful clearing of all cannulas and syringes using

fresh sterile distilled water Prophylactic postop topical antibioticAvoid swimming for 1month postoperatively

Microbial Keratitis

Diffuse lamellar keratitis

Also known as ‘Sand of Sahara’Non infectious complication Infiltration of inflammatory cells in interface

Possible causes:Retained meibomian secretionsMetallic debrisTalc from glovesLubricants on the microkeratome or bladesTopical medications such as anestheticsEndotoxinsIL 1 released from corneal epithelial cells

following cell injury or death

Linebarger staging of DLK

Stage 1Fine white cells of granular appearance distributed

in wave like fashion in periphery of flapFrequently occurs on day1No decrease in BCVA

Mx:Frequent administration of topical steroids

Stage 2Whitish cells of granular or wave like

appearance in visual axis and possibly at the periphery

Typically seen 2 or 3 days post LasikNo decrease in BCVA

Mx:Frequent administration of topical steroids

Linebarger staging of DLK

Stage 3Increased density of cells in visual axis, more

clumped than wave likeTransparent peripheral corneaSeen on day 3 0r 4Patient may describe fogginess of vision

Linebarger staging of DLK

Mx:Raise the flap and

thoroughly irrigate with BSS

Frequent administration of topical steroids

Stage 4Central corneal melting at interface by release of

collagenase by aggregated inflammatory cellsScarrings and folds in visual axisVA is decreased, hyperopic

shiftIrregular astigmatism

Mx:When repair process has

concluded, consider anterior lamellar keratoplasty

Linebarger staging of DLK

Late Postoperative Complications

Epithelialization of interface

Causes:Prolonged manipulation

of the flapExcessive use of

instruments at the interface

Poor flap edge adhesionEpithelial abrasion at

flap edgeFlap misalignmentButtonholesSpillover of ablation at

bed margin

Results:Decreased visual

acuityIrregular astigmatismDiscomfortRisk of stromal melt

Machat classification of Epithelial Ingrowth

Grade 1:Small white aggregates

with smooth outlinesLimited to 2mm from

the flap edgeOften outlined by white

demarcation line along the front of epithelial progression

No treatment required Normally disappear

within 2-4 months

Grade 2:Pearly white

aggregates with blurred edges

Located within 2mm from the flap edge

Ingrowth is thickerMy progress toward

centre of pupilRequires

observation

Machat classification of Epithelial Ingrowth

Grade 3:Ingrowth is marked

with multicellular thickness

Extent exceeds 2mm from the flap margin

Thinning or melting of flap may occur

Machat classification of Epithelial Ingrowth

Prevention:Avoid prolonged manipulation of flapClear any epithelium, tags, or debris from

stromal bed prior to flap repositionShield hinge areaApply contact lens when epithelial defects are

observedFemtosecond laser flap is better

Mx

For peripheral few aggregates: NdYAG laser30-40 pulses; 0.6-1.2mJ; beam focussed slightly

posteriorly with respect to the epithelial growth

Sufficient for blocking progression

Mx

For extensive aggregates:Raise the flap closest to epithelial growthDebride the stromal surface and undersurface of

flap edges with microspatulaIn severe ingrowth with melting and folds it is

better to remove the flap and allow healing

Refractive Complications

Irregular astigmatism

Causes:Wrinkles or folds in flapInterface debrisEpithelial ingrowthDecentration

Results:VA decreased by 2 or more lines Mx:Retreatment is directed to underlying cause

Undercorrection

There is residual, unexpected refractive error in first postoperative month

More frequent in high myopia above 10 to 12DIt is easier to correct residual myopia than to

correct hyperopia from overcorrection

Causes of undercorrection:Incorrect preoperative refraction (most

common)Difficulty in performing precise refractive

evaluation(severe myopia with staphyloma)Incorrect laser calibrationEnvironmental condition in OTIncorrect data entryIncomplete or decentered ablationIncorrect interpretation of nomogramUnstable ametropia

Undercorrection

Mx: Retreatment should be considered 2 to 3

months later, after refractive stability Preferably under aberrometric guidance

Options: Lifting the flap and reablation

Usually performed within 3 to 4mths of first treatment

Lamellar technique or recutting a new flap(for myopia greater than 10D)

Performed atleast 6months after initial treatment May not be possible due to already thinned cornea

Surface ablation technique(PRK)

Overcorrection

1 month after surgery ,there is refractive correction that exceeds the expected value

Causes:Incorrect preoperative refractionIncorrect data entryPoor control of humidity levels in laser

room(too dry)

Mx: Lifting the flap and reablation

It is possible to repeat the treatment for hyperopic values in 2 to 3months

Paraperipheral ablation of anterior stromal bed is done

Hyperopic surface photoablation Hyperopia of 1 to 3D can be corrected

Conductive keratoplasty

Regression

Indicates that the refractive result of Lasik is not stable with continuing loss of effect over a few months

Normally stops between 1 and 3 mths after surgery

More frequent in myopia >10DFrequently seen in severe hyperopia and

astigmatism

Causes:May be due to combination of epithelial

hyperplasia and remodeling of stroma

Management:Treatment options as for undercorrectionEnhancement procedures to be considered

only after refraction is stable

Regression

Corneal Ectasia

Progressive relaxation of the cornea with an increase in radius of curvature along with thinning

Progressive deterioration of patient’s VA

Pathophysiology:Collagen fibres in anterior third of cornea have

greater tensile strengthIn LASIK, cut is performed in the anterior thirdCorneal weakening by 0-33%Ectasia: delamination and interfibril fracture

Corneal Ectasia

Risk factors-KeratoconusPellucid marginal degenerationForme fruste keratoconusResidual stromal bed less than 250μm in diseased

corneas

Refractive instability and family history of keratoconus should arouse suspicion

Corneal Ectasia

Results:Thinning and bulging of corneaMyopic shiftIrregular astigmatismReduced UCVA and BCVA

Corneal Ectasia

Diagnostic criteria for corneal ectasia:

1. Inferior topographic steepening of >5D compared with immediate postoperative appearance

2. Loss of >2snellens line of UCVA3. Change in manifest refraction >2D(sph/cyl)4. Posterior float higher than 0.08 mm

Corneal Ectasia

Prevention:Alternative approach- PRK/ Phakic IOL

Preoperative: Topography:

In asymmetric cornea –test should be repeated several times

CL wearers should stop using CL 2-3wks before topography

Rule out keratoconusPachymetry:

Most important to plan ablation

Corneal Ectasia

Intraoperative:Measure flap thickness and posterior stroma

during surgery, both before and after the ablation

Corneal Ectasia

Mx:Collagen crosslinkingRGP contact lensIntrastromal ringsLamellar keratoplastyPenetrating keratoplasty

Corneal Ectasia

Decentered Ablation

Causes:Poor patient fixation

due to nervousness or oversedation

Difficulty seeing target due to blurred vision(high corrections)

Results:Loss of BCVAIrregular astigmatismNight vision problemsGhosting, glare

Decentered Ablation

Treatment:For mild degrees of decentration, a small

diameter ablation may be performed at the edge of the original optical zone to enlarge the optical zone in pupillary axis

A series of 3 small diameter ablations may be placed at the edge of decentered ablation followed by PTK smoothing

Decentered Ablation