lasik: complications and their management
DESCRIPTION
LASIK: COMPLICATIONS AND THEIR MANAGEMENTTRANSCRIPT
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LASIK: COMPLICATIONS AND THEIR MANAGEMENT
Dr. Rujuta GoreDr. Rujuta Gore
Dr. Mrudula BhaveDr. Mrudula Bhave
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LASIK: Possible complications
IntraoperativeMicrokeratome relatedFlap related
Early postoperativeLate postoperativeRefractive complications
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Intraoperative complications
Inadequate exposure
Inadequate suction
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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
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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
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Thin/ Perforated cut (buttonhole)Mechanical Causes:
Inadequate suction Incorrect ring sizePoor blade quality Excessively dry corneaLoose epitheliumEdematous epithelium
Anatomical causes:Very steep corneasIrregular astigmatism
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Results:Inability to perform laser ablationRisk of epithelial ingrowth in interface and
possible melting Risk of irregular astigmatism
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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
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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
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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
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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
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Early Postoperative Complications
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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
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Flap Complications
Displacement of flapWrinkled flap (micro and macrostriations)Interface debrisFlap edemaFlap shrinkageFlap stretchingDecentration
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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
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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
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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
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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
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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
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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
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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
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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
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Symptoms:Increased light sensitivity PainRedness Foreign body sensationDecreased vision
Microbial Keratitis
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Clinical signs:Corneal infiltrate
Epithelial ingrowth
Epithelial defects
AC reaction
Hypopyon
Microbial Keratitis
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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
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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
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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
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Diffuse lamellar keratitis
Also known as ‘Sand of Sahara’Non infectious complication Infiltration of inflammatory cells in interface
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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
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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
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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
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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
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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
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Late Postoperative Complications
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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
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Results:Decreased visual
acuityIrregular astigmatismDiscomfortRisk of stromal melt
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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
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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
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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
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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
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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
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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
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Refractive Complications
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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
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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
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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
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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)
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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)
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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
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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
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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
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Corneal Ectasia
Progressive relaxation of the cornea with an increase in radius of curvature along with thinning
Progressive deterioration of patient’s VA
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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
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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
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Results:Thinning and bulging of corneaMyopic shiftIrregular astigmatismReduced UCVA and BCVA
Corneal Ectasia
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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
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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
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Intraoperative:Measure flap thickness and posterior stroma
during surgery, both before and after the ablation
Corneal Ectasia
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Mx:Collagen crosslinkingRGP contact lensIntrastromal ringsLamellar keratoplastyPenetrating keratoplasty
Corneal Ectasia
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Decentered Ablation
Causes:Poor patient fixation
due to nervousness or oversedation
Difficulty seeing target due to blurred vision(high corrections)
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Results:Loss of BCVAIrregular astigmatismNight vision problemsGhosting, glare
Decentered Ablation
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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
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