Lasers in Glaucoma Presenter:Dr.Parth Satani Moderator:Dr.Rita Dhamankar
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.
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