Lasers in Glaucoma

Presenter:Dr.Parth SataniModerator:Dr.Rita Dhamankar

Introduction A laser is a device that emits light through a process

of optical amplification based on the stimulated emission of electromagnetic radiation.

Properties of laser Monochromatic CoherentParallelismBrightness

Lasers used in glaucoma

488 - 514 nm - Argon blue-green & green 810 nm Diode1064 nm - Nd:YAG 10,600 nm - Carbon dioxide

Different types of laser

Carbon Dioxide

Neon

Helium

Krypto n

Argon

Gas

Nd Yag

Ruby

Solid S tate

Gold

Copper

MetalVapour

Argon Fluoride

EXCIM ER Dye Diode

LASERS

Three basic light-tissue interactions

PhotocoagulationLaser light is absorbed by the target tissue or by

neighboring tissue, generating heat that denatures proteins (i.e., coagulation)

Photodisruption Power density is so great that molecules are broken

apart into their component ions, creating a rapidly expanding ion ‘plasma.’ This ionization and expanding plasma create subsequent shock-wave effects which cause an explosive disruption of tissue to create an excision

Photoablation:breaks the chemical bonds that hold tissue

together, essentially vaporizing the tissue

Modes of operation Continuous Wave (CW) Laser: It delivers the energy in a

continuous stream of photons. Pulsed Lasers: Produce energy pulses of a few micro to

milliseconds. Q Switched Lasers: Deliver energy pulses of extremely

short duration (nanosecond). Mode-locked Lasers: Emits a train of short duration pulses

(picoseconds to femtoseconds)

Lasers in Open angle glaucomaOutflow enhancement

Laser trabeculoplastyInflow reduction

Cyclophotocoagulation(for end stage disease)

Lasers in Angle closure glaucomaRelief of pupillary block

Laser iridotomyModification of iris contour

Laser iridoplastyInflow reduction

Cyclophotocoagulation(end stage disease)

Lasers in Post-operative treatmentLaser suture lysis

Adjacent to trabeculectomyLaser sclerostomyLaser gonio-puncture

Adjacent to non-penetrating surgery

Nd:YAG laser Beckman and Sugar in 1973 were first to use Nd:YAG

laserNeodymium crystal is embedded in yttrium-aluminium

garnetIt can be operated in

Free modeQ-switchedMode locked regime

Free mode has thermal effect on tissueWhile Q-switched and mode locked have photo

disruptive effect.

Q-switched and mode locked regimetruly pulsed lasers with emissions of high power density

in very short duration.Q-switched system

energy within the laser cavity is raised several times by making the usually partially reflective mirror totally opaque.

Then suddenly making it transparent again by using polaroid filters

So there is rapid depletion of energy confined within laser cavity.

Q-switched Mode lockDuration 10-20ns 30-70nsIrradiance 106 109Optical switching Pockel cell/dye DyeEfficiency Better Poor

•In pockel cell - optical switching occurred by electrical modulation•While in dye - optical switching occurs when the energy buildup becomes very high •So dye driven switches are inefficient and prone to malfunctioning.

Laser iridotomyLaser treatment to connect anterior and

posterior chamber to relieve pupillary block.Effective for pupillary blockRelatively non invasivePreferable to surgical iridotomy

indicationDefinitive indications

Acute angle closure.Chronic (creeping) angle closureMixed mechanism glaucomaPhacomorphic with an element of pupillary

blockIris bombé

Relative indicationsCritically narrow angles in asymptomatic

patientsYounger patients, especially those who live

some distance from medical care or who travel frequently

Narrow angles with positive provocative testIris–trabecular contact demonstrated by

compression gonioscopy

Types of laserPhotodisruptive Nd:YAG laser,(Q-switched and mode-

lock)

The photothermal argon lasers

Patient preparationPilocarpine 1% is instilled twice, 5 minutes apart;

miosis helps to stretch and thin the iris.Proparacaine 0.5% drops are instilled immediately

before the procedure

Lens choiceAbraham lens- 66D planoconvex button. The Wise lens -103D planoconvex button,

concentrates the laser energy more it minimizes the spot and magnifies the target even

moredifficult to focus.

Advantage of the Abraham lens -energy delivered to both cornea and retina is four times less than that with Wise lens.

Specific techniquesPlace- peripheral iris under the upper eyelid to avoid

ghost images that may arise through the iris hole. Iris crypts represent thinner iris segments and, as

such, are penetrated more easily. The superonasal position (at 11 and 1 o’clock) is the

best position to use to prevent inadvertent irradiation of the fovea

Laser Iridotomy - position

Nd-YAG laserThe energy- 3–8 mJ,Pulses- there are 1–3 per shot, and one or more shots

are used for penetration The Q-switched mode is usedPlace-between the 11 and 1 o’clock positions,Iris blood vessels are avoided

Argon laserLong pulses (0.2 seconds) for light-colored irides

(blue, hazel, light brown), short pulses (0.02–0.05 seconds) for dark brown

irides.Power; 1000 mW Spot size ; 50 μmsingle area is treated with superimposed applications

until perforation is obtained pigment flume is found to move forward (“smoke sign”

or “waterfall sign”)

Del Priore L.V., Robin A.L., Pollack I.P.: Neodymium:YAG and argon laser iridectomy: long term follow-up in a prospective randomized clinical trial.  Ophthalmology  1988; 95:1207-1211

Post laser managementSteroids are given 4 times a day for 7 days to

reduce post laser inflammation .Anti-glaucoma medication like B-blockers are

given 2 times a day for 7 days to reduce chances of post laser IOP spike.

Patient is re-checked after 7 days for IOP and patency of iridotomy.

Argon versus Nd:YAG Laser.

Argon laser Nd:YAG laser

Uptake of energy Require pigmented cells

Doesn’t require

Iris colour Dark brown Light and medium colour iris

Late closure High chance Less chance

Combined Argon Nd:YAG techniqueUsed in sequential combination for dark brown irides

or for patients who are on chronic anticoagulant therapy

First, the argon laser (short-pulse mode) is used to attenuate the iris to about one fourth the original thickness and to coagulate vessels in the area.

Then Nd:YAG laser is used, with the beam focused at the center of the crater; one or more bursts are used to complete the iridectomy.

ComplicationsIntraocular Pressure SpikesLaser-Induced InflammationIridectomy FailureDiplopiaBleedingLens OpacitiesCorneal Injury

Laser peripheral iridoplasty

It is an effective means of opening an appositionally closed angle.

Procedure consists of placing contraction burns in the extreme periphery to contract the iris stroma between the site of burn and the angle so it physically opens an angle.

Argon laser are used with the lowest power setting that creates contraction of the iris

Laser Iridoplasty

Note the almost Ring like burns for laser iridoplasty

Spot size : 100–200- µm Power: 100–30o mW Duration : 0.1 second.Lighter irides will require slightly higher energy levels

than darkerTen to twenty spots evenly distributed over 360º of

the iris are usually sufficient

IndicationAttack of angle closure glaucomaPlateau iris syndrome commonest indicationAngle closure related to size or position of lensNanophthalmosFacilitate access to the trabecular meshwork for laser

trabeculoplastyMinimize the risk of endothelial damage during

iridotomy

Contraindications Contraindication

Advanced corneal edema or opacificationFlat anterior chamberSynechial angle closure

Complication: mild iritisCorneal endothelial burnTransient rise in IOP

Laser trabeculoplastyRelatively effective,non-invasive.Laser treatment to trabecular meshwork

increase to increase outflow.

Mechanism of actionWise and Witter proposed that thermal energy

produced by absorption of laser by pigmented trabecular meshwork caused shrinkage of collagen of trabecular lamellae this opened up intertrabecular space in untreated region and expanded schlemm’s canal by pulling the meshwork centrally

Elimination of some trabecular cells posttrbeculoplasty.this stimulate remaining cells to produce different composition of extracellular matrix with lesser outflow obstructing properties.

Laser trabeculoplasty Method

Argon laser trabeculoplastySelective laser trabeculoplasty

Lens Goldmann 3 mirror lens Latina trabeculoplasty lens:

Argon laser trabeculoplastyLaser parameter

Power -300-1200mW Spot size—50µm Duration -0.1 sec Number of burns-30-50 spots evenly placed over

180deg. remaining in subsequent visit.

Argon laser trabeculoplasty Ideally,spot should be appliedOver schlemm’s canal avodingThe iris root at the junction of Anterior 1/3 to posterior 2/3 of Meshwork.The energy level should be set To induce a reaction from a Slight transient blanching of The treated area to small Bubble formation

Selective laser trabeculoplastySLT target pigmented trabecular meshwork cells

without causing thermal damage to non-pigmented cells or structure.

Laser :Frequency doubled Q switched ND:YAG laser

Pulse :3nsec.Spot size 400 µm Power :o.8 mJ power No.of spots :apprx.50 spots are appliedEnd point :minimal bubble or no bubble

  Selective laser trabeculoplasty (arrow) versus argon laser trabeculoplasty treatment (arrowhead).  (Courtesy of M. Berlin, MD.)

ComparisonALT SLT

TYPE OF LASER Argon blue green 488/514nm

Double frequency Nd:YAG 532nm

Spot size(µm) 50 400Duration 0.1s 3nsPower 300–900 mW 0.6–1.2 mJDegrees 180 180–360

IndicationsChronic open angle glaucomaExfoliation syndromePigmentary glaucomaGlaucoma in aphakia or pseudophakia

ContraindicationsClosed or extremely narrow anglesCorneal edemaAphakia with vitreous in ant.chamberVascular glaucomaAcute uveitisPrimary congenital glaucomaAngle recession glaucoma

Complications Most common risk is IOP spikes in about 3–5% of

patientsIritisPeripheral ant.synechiaeHemorrhage Corneal complicationWaning of response

ComparisonALT maintained IOP control in 67–80% of eyes for 1

year, in 35–50% for 5 years, and in 5–30% for 10 years (i.e., an attrition rate of 6–10% per year).

With SLT, IOP lowering occurs within 1–2 weeks; IOP lowering can continue for up to 4–6 months post-treatment and also continues for 3–5 years with a similar attrition to ALT

Shingleton B.J., Richter C.U., Belcher C.D., et al: Long-term efficacy of argon laser trabeculoplasty.  Ophthalmology  1987; 94:1513-1518

Weinand F.S., Althen F.: Long-term clinical results of selective laser trabeculoplasty in the treatment of primary open angle glaucoma.  Eur J Ophthalmol  2006; 16:100-104.

Lasers in malignant glaucomaArgon laser Power :200–800 mWDuration :0.1 second spot size :100–200- µm. This may restore the normal forward flow of aqueous,

especially when accompanied by aggressive cycloplegic, mydriatic, and hyperosmotic therapy

The Nd:YAG beam is directed at the anterior hyaloid face between the ciliary processes using a single burst at power settings used for posterior capsulotomy.

In aphakic ciliary block glaucoma the Nd:YAG laser can rupture the vitreous face and break the block.

Pseudophakic ciliary block glaucoma can also be treated with a Nd:YAG laser by rupturing anterior hyaloid .

Rupture of the posterior capsule may be needed to break the block in some cases

CyclophotocoagulationReduce aqueous production by destruction of

ciliary epitheliumTechniques

Transscleral Transpupillary Endolaser

Indication Failure of multiple filtering surgeries Primary procedure to alleviate pain in neovascular

glaucoma with poor visual potential. Painful blind eye Surgery not appropriate

CyclophotocoagulationTrans-scleral cyclophotocoagulation

destroys ciliary epithelium and associated vasculature decreased aqueous humor production.

Nd:YAG laser – good scleral penetration light energy is absorbed by blood and pigment of the

ciliary body. Diode laser (810 nm) has lower scleral transmission

than the Nd:YAG laser (1064 nm) but greater absorption by melanin.

So use of 50% less energy compared to the continuous wave Nd:YAG laser to achieve the same effect

CyclophotocoagulationTrans-scleral Cyclophotocoagulation

Noncontact Nd:YAG laser cyclophotocoagulation Contact Nd:YAG laser cyclophotocoagulation Semiconductor diode laser trans-scleral

cyclophotocoagulation Endoscopic cyclophotocoagulation

CyclophotocoagulationNoncontact Nd:YAG laser

cyclophotocoagulation Nd:YAG laser is mounted on slit-lamp 4–8 J/pulse, duration :20 msplaced 1.0–1.5 mm posterior to the limbus total of 30–

40 spots 3 and 9 o’clock positions spared to avoid long

posterior ciliary arteriesA contact lens may be used to blanch blood vessels to

improve the focus Atropine 1% and prednisolone acetate 1% are

prescribed four times a day; these are tapered as inflammation subsides.

CyclophotocoagulationContact Nd:YAG laser cyclophotocoagulation

Nd:YAG laser in the continuous mode via a fiber optic system in direct contact with the conjunctiva

The fiber optic laser probe is positioned perpendicularly on the conjunctiva with the anterior edge 0.5–1.0 mm posterior to the surgical limbus.

power level of 4–9 W and duration between 0.5 and 0.7 seconds

CyclophotocoagulationSemiconductor diode laser trans-scleral

cyclophotocoagulation most widely used method of ciliary ablation with

reported success rates ranging from 40% to 80%. it is semiconductor diode laser (wavelength 810

nm) 1500–2500 mW for 1.5–3 seconds and a total of 18–

24 spots

ENDOSCOPIC LASER CYCLOPHOTOCOAGULATION

ENDOSCOPIC LASER CYCLOPHOTOCOAGULATIONPerformed with an 810 nm diode laserXenon light source that provides illumination and a

helium-neon laser aiming beam starting settings are 0.25 W with continuous exposure

time. The actual time of exposure is based on visual effect

of ciliary process shrinkage and whiteningTypically, as much of the ciliary process is treated as

possible, as there is a significant portion posteriorly that is usually not treated

cycloplegics are not necessary and steroids are used in the usual postoperative dosing

Comparison

Complications Conjunctival burn Hyphema Inflammation Pain IOP spike Cataract Pupil abnormality

Hypotony Need for re-treatment Loss of visual acuity Vitreous hemorrhage Choroidal

detachment Phthisis

CO2 Laser Assisted Sclerectomy SurgerySimilar to trabeculectomy

Major difference being that after the scleral flap is raised, the remaining sclera over the Schlemm’s canal and trabecular meshwork is dissected by the CO2 laser probe until aqueous percolated over the entire dissected bed.

Aimed to prevent intra ocular complications.Performed under sub-conjunctival anesthesia.

CO2 Laser Assisted Sclerectomy Surgery

Drawbacks Demands careful and delicate surgeryRelatively long learning curveCan be performed only by highly skilled

surgeons,

Laser suture lysisSubconjunctival trabeculectomy flap sutures can be

lysed with the laser postoperatively if there is inadequate filtration

Dark nylon or proline sutures can usually be severed with the argon laser

settings of 200–1000 mW for 0.02–0.15 second with a 50–100-µm spot size

feasible from about 3–15 days after surgery or up to at least 2 months or more after mitomycin-C use

Singh J, et al: Enhancement of post trabeculectome bleb formation by laser suture lysis, Br J Ophthalmol80:624, 1996.

Method

Laser suture lens. The device has a small convex lens that compresses the edematous conjunctiva permitting a clear view of the tiny nylon suture underneath the conjunctiva. This suture then can be cut easily with a 50-µm spot laser beam using 400 mW of energy for 0.1 second.(Photo courtesy of John Hetherington Jr, MD, University of California,San Francisco.)

Dense hemorrhage in the tissues overlying the suture will absorb the energy, prevent treatment, and possibly cause conjunctival perforation.

fluorescein-stained conjunctiva limits argon laser energy transmission to the sutures and may cause conjunctival perforation.

thick, inflamed Tenon’s capsule may also preclude successful LSL

After laser steroid is given to reduce external scarringAdditional suture can be lysed 1-2 days after

Reopening of failed filtration siteFiltering sites can close because of fibrosis on the

external sideMembrane formation or iris incarceration on the

internal side of the sclerostomyArgon or Q-switched Nd:YAG laser can vaporize it

With the argon laser, settings of 300–1000 mW at 0.1–0.2 second with a 50–100-µm spot

The Nd:YAG laser is also useful in opening an obstructed sclerostomy

Single bursts of 2–4 mJ are delivered via a Nd:YAG coated goniolens to disrupt any translucent membrane obstructing it.Kandarakis A, et al: Reopening of failed trabeculectomies with ab interno Nd:YAG laser, Eur J

Ophthalmol 6:143, 1996.

Femto laser in the offing Applications for the femto laser ab externo

includeCreating trabeculectomy flaps, Non-penetrating procedure flaps,Near-perforating deep excisions under flaps, Removal or thinning of trabecular meshwork and

the inner wall of Schlemm’s canal, and creating suprachoroidal fistulae

Excimer Laserab interno procedures include

ELT (excimer laser trabeculostomy) equivalent using docked gonio lens delivery systems

To Create full thickness or near full thickness scleral windows for trabeculectomy

To create suprachoroidal fistulae.

Cyclodialysis and laserCyclodialysis clefts have been both opened and closed

with laserArgon laser photocoagulation using thermal burns of

0.1 second 100-µm spot size, and 500 mW can be used to close cyclodialysis clefts and reduce hypotony

Nd:YAG is used to open cleft.

Closure of a cyclodialysis cleft. The beam is aimed deep into the cleft to create an inflammatory response and generate closure.Postoperative mydriasis and cycloplegia may aid this process.

Laser synechiolysisThe argon laser can be used to pull early or lightly

adherent peripheral anterior synechiae away from the angle or cornea.

(400–800 mW, 0.1–0.2 second,50–100-µm spot sizeIt is simillar to iridoplastyHelpful to break and arrest formation of iridocorneal

adhesions after penetrating keratoplasty or other forms of peripheral anterior synechiae.

Chronic synechiae can be very resistant to argon iridoplasty.

The Nd:YAG laser can lyse iris adhesion. Use- early irido–corneal–endothelial (ICE) syndrome

to disrupt synechiae,Side-effect is bleeding.

GoniophotocoagulationUse - anterior segment neovascularizationGoniophotocoagulation is useful to obliterate fragile

vessels in a surgical wound like in cataract incisions or trabeculectomy or goniotomy wounds

Argon laser 100-µm spot size for 0.1–0.2 second and 300–500 mW of energy will usually obliterate these vessels

Bleeding is common,Gross hyphema may occur

Other uses of lasersGoniopunctures in NPGS is mandatory, after a

while, as during the surgical procedure itself, the AC is left alone.

Goniopunctures are done with a YAG LaserThese help passage of aqueous into the scleral

lake.Blocked inner ostium can be freed by Yag

Laser, post trabeculectomy.Vitriolysis , in case of a vitreous tag sticking

out, can be done using a YAG laser.Modifying bleb by lasers after staining the

bleb with gention violet.

Goniopuncture

Lasering the bleb

Lasers in Glaucoma -SummarizingLasers in glaucoma are an important part of

the armamentarium in the management.Several situations exist when laser therapy

may prove beneficial to the control of intraocular pressure, in association with medical therapy and may enhance quality of life by preserving visual function.

Thank you