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Lasers in Glaucoma Dr Premanand C
LASERL - Light A - Amplification byS - StimulatedE - Emission ofR - Radiation
Properties:Coherent - synchronisedCollimated directionality is parallelMonochromatic photons of one wavelengthHigh intensity
Thermal effect: Photocoagulation (Argon, Diode & Krypton) Photovaporization (CO2 , Erbium YAG & Holmium YAG)
Ionizing effect: Photodisruption (Nd YAG)
Chemical effect: Photoablation (Excimer)Tissue effects
Lasers in glaucomaTherapeutic 2. DiagnosticConfocal scanning laser ophthalmoscopy: Heidelberg Retinal Tomography (HRT)Scanning laser polarimetry: GDxOptical coherence tomography: OCT
Laser TypeWavelength nmTissue InteractionClinical UseYAGInfra-red1054, used Q switchedPhotodisruptionPI, Goniopuncture,Synechiotomy, Hyaloidotomy,CyclodestructionArgonVisible Spectrum,488-514nmPhotocoagulationSuturelysis, PI,IridoplastyDiodeInfra-red, 810 nmPhotocoagulationTSCPCSelectiveFrequency doubled Yag, 532 nmSelective photo thermolysisSLTExcimer (XeCl)UV, 308 nmPhotoablationTrabeculostomyCO2Infrared, 9140-10600 nmPhotovapourisationLaser assisted deep sclerectomy
Laser IridotomyIridoplastyTrabeculoplasty - ALT & SLTCyclophotocoagulation Laser suturelysisLADS (laser assisted deep sclerectomy)Anterior hyaloidotomy
Peripheral Iridotomy
PACPACGFellow eye of acute angle closurePupillary blockNanophthalmosMicrosperophakia Malignant glaucomaPlateau iris syndrome? Pigmentary glaucoma
IndicationsPACS - strong family history of ACG need for repeated dilated exam poor access to Ophthalmic care
Creation of a hole in peripheral iris Equalisation of IOP in AC and PCThereby leading to deepening of AC and roll-back of irido-trabecular contact Principle
Explain the procedureA drop of pilocarpine 2% is instilled 3-4 times, 15 minutes apart A drop of Apraclonidine 0.5% or brimonidine 0.2%Proparacaine 0.5% drops are instilled immediately before the procedure
Patient preparation
Laser settings
Sequential laser:Argon laser - coagulate, stretch and thin target areaNd YAG - penetrate the thinned out target area
Nd YAGArgon5-7 mJ1-3 pulses per burst500- 750mW50 spot size0.1 - 0.2 sec duration
YAGArgonLess tissue destructionTissue destruction at margin, oedemaLess iritisMore iritis, IOP spikePupillary distortionLess frequent closureFrequent closureFrequent bleedingLess bleedingEffective in lighter iridesMore effective in dark irides
Sit comfortablyMiosisLook for crypts (superior 1/3 desirable)Posterior defocusAbraham lens (+66D)Focus the beam within the iris stroma End pt - sudden gush of aqueousSize - 150
Procedure
Abraham lens66D plano convex Produces a convergent beam and increases the power intensity Acts as a heat sink for the corneakeeps eye openStabilises the eye, controls movementMagnifies area of iris selected for PIStops bleeding
Check IOP after 1hrTopial steroid 4/day - 1 weekAGM based on pre laser IOP
Post PI
Temporary blurring of visionBleedingIOP spikesInflammationCorneal endothelial burnsClosure of iridotomyGhost image, glare & diplopia
Complications
PI patencyIOPGonioscopy - opened / occludableDilate Fundus evaluationVisual fieldsTreat
Follow up - 1 week
Iridoplasty
Plateau iris syndromeNanophthalmos
Acute ACG with shallow AC IndicationsPost PI
Laser settings: Power: 200 - 400 mW Spot size: 500 Duration - 0.5sec
20-25 evenly spaced spots over 360 degree End pt - brisk constriction of iris
Procedure
Laser Trabeculoplasty
Types: Argon laser trabeculoplasty Selective laser trabeculoplasty Micropulse diode laser trabeculoplasty Excimer laser trabeculoplasty
ALT (488-514nm): Absorption of laser by pigmented TM collagen shrinkage of trab lamellae which opens intertrabecular spaces in untreated areas and expands schlemms canal Activates phagocytosis
SLT (532nm): Selective Photothermolysis Selectively absorbed by melanin in TM Stretching of trabecular beams, increased mobility, release of chemical mediators and stimulates endothelial replication Mechanism
ALT vs SLTALTSLT50m400mALTSLT
ALTSLTEnergy500 1,000 mW0.8 1.5 mJSpot size50 micron400 micronPulse duration100 ms3 ns
Open angle glaucomas:
POAG Exfoliation syndrome Pigmentary glaucoma Glaucoma in aphakia, pseudophakia
Supplement medical therapy and postpone surgery Primary therapy when there is poor drug compliance Additional IOP lowering after trabeculectomy Indications
Closed angles Corneal haze Aphakia with vitreous in AC NVG Active uveitis Angle recession glaucoma Congenital glaucomas
Contraindications
Procedure
Goldmann 3 mirror Ritch trabeculoplasty lens
50 contiguous, non overlapping spots 180 degree End pt - transient blanching or bubble formation
Advantage of SLT over ALT:
SLT is selective:SLT selectively targets only the melanin-rich cells of the trabecular meshwork
SLT is non-thermal:The short pulse duration of SLT is below the thermal relaxation time of the TM tissue, thereby eliminating the incidence of thermal damage
SLT is repeatable:SLT treatment can be repeated without causing harm or further complicationsALTSLT
Cyclophotocoagulation
Types:Transpupillary CPC (Argon 488 nm)Trans scleral CPCNoncontact - Nd:YAG (1064nm)Contact - Diode (810nm), Nd:YAGEndoscopic CPC (Diode laser, 810nm)
Intractable glaucoma:
Neovascular glaucoma Traumatic glaucoma Aphakic glaucoma Congenital glaucoma Penetrating keratoplasty Silicon oil Eyes with limited vision potential and uncontrolled IOP Painful blind eyes due to raised IOP
Indications
TSCPCDiode laser 810nm Fibre-optic probe (G probe)2000 - 2500 mW 2000 ms (2sec)Reduce power if audible pops18-20 burns; sparing 3 and 9 oclockDestroys ciliary epithelium, stroma & vascular supply - lowering IOPRetreatments possibleLocal anaesthesia
Complications:Moderate to severe iritis, IOP spikePain Loss of vision, Hypotony & phthisis
TSCPC
Endo cyclophotocoagulation Has the advantage of directly visualising the ciliary body while delivering laser Disadvantage it is invasive and requires a sterile environmentEntry either corneal or pars planaLatter requires limited vitrectomyComplications: CMO, fibrin exudates, hyphaema
TSCPC vs ECP
AdvantagesDisadvantagesTSCPCExtraocular procedureDestruction of adjacent tissuesOPD basisHigher energy deliveredEaseHigher complication ratesECPLess collateral damageIntraocular procedureTitrateIOP spikesDirect visualizationExpensive
Argon laser -Suturelysis
At the slit lamp, one suture at a timeHoskins or Ritch lensNo coupling gel required50 X 0.1 0.2 sec X 300-700 mWComplications - hypotony, failure, button holing of conjunctiva
YAG laser hyaloidotomyYAG laser hyaloidotomy to break the anterior vitreous face (with posterior capsulotomy) to abort aqueous misdirection in pseudophakic eyes
CO2 or Erbium YAG laser (photovaporisation) After completing superficial flap dissection Laser used to ablate deep sclera in a controlled manner Schlemms canal is unroofed Aqueous come in contact with the laser and absorbs it thereby terminating the preocedure
LADS (laser assisted deep sclerectomy)
Thank you!