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!