Lasers in Glaucoma

Lasers in Glaucoma

Presenter:Dr.Parth Satani

Moderator:Dr.Rita Dhamankar

Introduction

A laser is a device that emits light through a process of opticalamplification based on the stimulated

emission of electromagnetic radiation.

Properties of laser

Monochromatic

Coherent

Parallelism

Brightness

Lasers used in glaucoma

488 - 514 nm - Argon blue-green & green

810 nm Diode

1064 nm - Nd:YAG

10,600 nm - Carbon dioxide

Different types of laser

Carbon Dioxide

Neon

Helium

Krypton

Argon

Gas

Nd Yag

Ruby

Solid State

Gold

Copper

Metal

Vapour

Argon Fluoride

EXCIMER Dye Diode

LASERS

Three basic light-tissue interactions Photocoagulation

Laser 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 continuousstream 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 glaucoma

Outflow enhancement

Laser trabeculoplasty

Inflow reduction

Cyclophotocoagulation(for end stage disease)

Lasers in Angle closure glaucoma

Relief of pupillary block

Laser iridotomy

Modification of iris contour

Laser iridoplasty

Inflow reduction

Cyclophotocoagulation(end stage disease)

Lasers in Post-operative treatment

Laser suture lysis

Adjacent to trabeculectomy

Laser sclerostomy

Laser gonio-puncture

Adjacent to non-penetrating surgery

Nd:YAG laser

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

Neodymium crystal is embedded in yttrium-aluminium garnet

It can be operated in

Free mode

Q-switched

Mode locked regime

Free mode has thermal effect on tissue

While Q-switched and mode locked have photo disruptive effect.

Q-switched and mode locked regime truly 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 polaroidfilters

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

Q-switched Mode lock

Duration 10-20ns 30-70ns

Irradiance 106 109

Optical switching Pockel cell/dye Dye

Efficiency 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 iridotomy

Laser treatment to connect anterior and posterior chamber to relieve pupillary block.

Effective for pupillary block

Relatively non invasive

Preferable to surgical iridotomy

indication

Definitive indications

Acute angle closure.

Chronic (creeping) angle closure

Mixed mechanism glaucoma

Phacomorphic with an element of pupillary block

Iris bombé

Relative indications

Critically narrow angles in asymptomatic patients

Younger patients, especially those who live some distance from medical care or who travel frequently

Narrow angles with positive provocative test

Iris–trabecular contact demonstrated by compression gonioscopy

Types of laser

Photodisruptive Nd:YAG laser,(Q-switched and mode-lock)

The photothermal argon lasers

Patient preparation

Pilocarpine 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 choice

Abraham lens- 66D planoconvex button.

The Wise lens -103D planoconvex button,

concentrates the laser energy more

it minimizes the spot and magnifies the target even more

difficult to focus.

Advantage of the Abraham lens -energy delivered to both

cornea and retina is four times less than that with Wise lens.

Specific techniques

Place- 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 laser

The 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 used

Place-between the 11 and 1 o’clock positions,

Iris blood vessels are avoided

Argon laser

Long 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 μm

single 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 management

Steroids 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 technique Used 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.

Complications

Intraocular Pressure Spikes

Laser-Induced Inflammation

Iridectomy Failure

Diplopia

Bleeding

Lens Opacities

Corneal 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 darker

Ten to twenty spots evenly distributed over 360º of the iris are usually sufficient

Indication

Attack of angle closure glaucoma

Plateau iris syndrome commonest indication

Angle closure related to size or position of lens

Nanophthalmos

Facilitate access to the trabecular meshwork for laser trabeculoplasty

Minimize the risk of endothelial damage during iridotomy

Contraindications

Contraindication

Advanced corneal edema or opacification

Flat anterior chamber

Synechial angle closure

Complication:

mild iritis

Corneal endothelial burn

Transient rise in IOP


Relatively effective,non-invasive.

Laser treatment to trabecular meshwork increase to increase outflow.

Mechanism of action

Wise 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.thisstimulate remaining cells to produce different composition of extracellular matrix with lesser outflow obstructing properties.


Method

Argon laser trabeculoplasty

Selective laser trabeculoplasty

Lens Goldmann 3 mirror lens

Latina trabeculoplasty lens:


Laser 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.


Ideally,spot should be applied

Over schlemm’s canal avoding

The 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 trabeculoplasty

SLT 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 applied

End point :minimal bubble or no bubble

Selective laser trabeculoplasty (arrow) versus argon laser trabeculoplasty

treatment (arrowhead). (Courtesy of M. Berlin, MD.)

Comparison

ALT SLT

TYPE OF LASER Argon blue green 488/514nm

Double frequencyNd:YAG 532nm

Spot size(µm) 50 400

Duration 0.1s 3ns

Power 300–900 mW 0.6–1.2 mJ

Degrees 180 180–360

Indications

Chronic open angle glaucoma

Exfoliation syndrome

Pigmentary glaucoma

Glaucoma in aphakia or pseudophakia

Contraindications

Closed or extremely narrow angles

Corneal edema

Aphakia with vitreous in ant.chamber

Vascular glaucoma

Acute uveitis

Primary congenital glaucoma

Angle recession glaucoma

Complications

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

Iritis

Peripheral ant.synechiae

Hemorrhage

Corneal complication

Waning of response

Comparison

ALT 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 glaucoma

Argon laser

Power :200–800 mW

Duration :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

Cyclophotocoagulation

Reduce aqueous production by destruction of ciliaryepithelium

Techniques 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


Trans-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


Trans-scleral Cyclophotocoagulation

Noncontact Nd:YAG laser cyclophotocoagulation

Contact Nd:YAG laser cyclophotocoagulation

Semiconductor diode laser trans-scleral cyclophotocoagulation

Endoscopic cyclophotocoagulation


Noncontact Nd:YAG laser cyclophotocoagulation Nd:YAG laser is mounted on slit-lamp

4–8 J/pulse,

duration :20 ms

placed 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 ciliaryarteries

A 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.


Contact 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


Semiconductor diode laser trans-scleralcyclophotocoagulation

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 CYCLOPHOTOCOAGULATION Performed with an 810 nm diode laser

Xenon 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 ciliaryprocess shrinkage and whitening

Typically, 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 SclerectomySurgery Similar to trabeculectomy

Major difference being that after the scleral flap is raised, the remaining sclera over the Schlemm’s canal and trabecularmeshwork 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 SclerectomySurgery

Drawbacks

Demands careful and delicate surgery

Relatively long learning curve

Can be performed only by highly skilled surgeons,

Laser suture lysis

Subconjunctival 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 scarring

Additional suture can be lysed 1-2 days after

Reopening of failed filtration site Filtering sites can close because of fibrosis on the external side

Membrane formation or iris incarceration on the internal side of the sclerostomy

Argon 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 include

Creating 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 Laser

ab interno procedures include

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

To Create full thickness or near full thickness scleralwindows for trabeculectomy

To create suprachoroidal fistulae.

Cyclodialysis and laser

Cyclodialysis clefts have been both opened and closed with laser

Argon laser photocoagulation using thermal burns of 0.1 second 100-µm spot size, and 500 mW can be used to close cyclodialysisclefts 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 synechiolysis

The 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 size

It is simillar to iridoplasty

Helpful 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.

Goniophotocoagulation

Use - anterior segment neovascularization

Goniophotocoagulation 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 lasers Goniopunctures in NPGS is mandatory, after a while,

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

Goniopunctures are done with a YAG Laser

These 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 -Summarizing Lasers 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.

Healthcare

Lasers in Glaucoma