Lasers in Glaucoma Presenter: Dr. David Luellwitz

Introducon

• A laser is a device that emits light through a process of opcal amplificaon based on the smulated emission of electromagnec radiaon. • Properes of laser • Monochromac • 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

LASERS

Gas Solid State Metal EXCIMER Dye Diode Vapour

Argon Ruby Copper Argon Fluoride

Krypton Nd Yag Gold

Helium

Neon

Carbon Dioxide Three basic light-ssue interacons • Photocoagulaon • Laser light is absorbed by the target ssue or by neighboring ssue, generang heat that denatures proteins (i.e., coagulaon) • Photodisrupon • Power density is so great that molecules are broken apart into their component ions, creang a rapidly expanding ion ‘plasma.’ This ionizaon and expanding plasma create subsequent shock-wave effects which cause an explosive disrupon of ssue to create an excision • Photoablaon: • breaks the chemical bonds that hold ssue together, essenally vaporizing the ssue Modes of operaon

— Connuous Wave (CW) Laser: It delivers the energy in a connuous stream of photons.

— Pulsed Lasers: Produce energy pulses of a few micro to milliseconds. — Q Switched Lasers: Deliver energy pulses of extremely short duraon (nanosecond).

— Mode-locked Lasers: Emits a train of short duraon pulses (picoseconds to femtoseconds) Lasers in Open angle glaucoma

• Oulow enhancement • Laser trabeculoplasty • Inflow reducon • Cyclophotocoagulaon(for end stage disease) Lasers in Angle closure glaucoma

• Relief of pupillary block • Laser iridotomy • Modificaon of iris contour • Laser iridoplasty • Inflow reducon • Cyclophotocoagulaon(end stage disease) Lasers in Post-operave treatment

• Laser suture lysis • Adjacent to trabeculectomy • Laser sclerostomy • Laser gonio-puncture • Adjacent to non-penetrang surgery Nd:YAG laser

• Beckman and Sugar in 1973 were first to use Nd:YAG laser • Neodymium crystal is embedded in yrium-aluminium garnet • It can be operated in • Free mode • Q-switched • Mode locked regime • Free mode has thermal effect on ssue • While Q-switched and mode locked have photo disrupve effect. • Q-switched and mode locked regime • truly pulsed lasers with emissions of high power density in very short duraon. • Q-switched system • energy within the laser cavity is raised several mes by making the usually parally reflecve mirror totally opaque. • Then suddenly making it transparent again by using polaroid filters • So there is rapid depleon of energy confined within laser cavity.

Q-switched Mode lock

Duraon 10-20ns 30-70ns

Irradiance 106 109

Opcal switching Pockel cell/dye Dye

Efficiency Beer Poor

•In pockel cell - opcal switching occurred by electrical modulaon •While in dye - opcal switching occurs when the energy buildup becomes very high •So dye driven switches are inefficient and prone to malfunconing. Laser iridotomy

• Laser treatment to connect anterior and posterior chamber to relieve pupillary block. • Effecve for pupillary block • Relavely non invasive • Preferable to surgical iridotomy indicaon

• Definive indicaons • Acute angle closure. • Chronic (creeping) angle closure • Mixed mechanism glaucoma • Phacomorphic with an element of pupillary block • Iris bombé • Relave indicaons • Crically narrow angles in asymptomac paents • Younger paents, especially those who live some distance from medical care or who travel frequently • Narrow angles with posive provocave test • Iris–trabecular contact demonstrated by compression gonioscopy Types of laser

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

• The photothermal argon lasers

Paent preparaon

• Pilocarpine 1% is inslled twice, 5 minutes apart; miosis helps to stretch and thin the iris. • Proparacaine 0.5% drops are inslled immediately before the procedure Lens choice

• Abraham lens- 66D planoconvex buon. • The Wise lens -103D planoconvex buon, • 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 rena is four mes 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 posion (at 11 and 1 o’clock) is the best posion to use to prevent inadvertent irradiaon of the fovea Laser Iridotomy - posion Nd-YAG laser

• The energy- 3–8 mJ, • Pulses- there are 1–3 per shot, and one or more shots are used for penetraon • The Q-switched mode is used • Place-between the 11 and 1 o’clock posions, • 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 applicaons unl perforaon 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 prospecve randomized clinical trial. Ophthalmology 1988; 95:1207-1211

Post laser management

• Steroids are given 4 mes a day for 7 days to reduce post laser inflammaon . • An-glaucoma medicaon like B-blockers are given 2 mes a day for 7 days to reduce chances of post laser IOP spike. • Paent is re-checked aer 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 sequenal combinaon for dark brown irides or for paents who are on chronic ancoagulant therapy • First, the argon laser (short-pulse mode) is used to aenuate 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. Complicaons

• Intraocular Pressure Spikes • Laser-Induced Inflammaon • Iridectomy Failure • Diplopia • Bleeding • Lens Opacies • Corneal Injury Laser peripheral iridoplasty

• It is an effecve means of opening an apposionally closed angle. • Procedure consists of placing contracon 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 seng that creates contracon of the iris Laser Iridoplasty

Note the almost Ring like burns for laser iridoplasty • Spot size : 100–200- µm • Power: 100–30o mW • Duraon : 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 Indicaon

• Aack of angle closure glaucoma • Plateau iris syndrome commonest indicaon • Angle closure related to size or posion of lens • Nanophthalmos • Facilitate access to the trabecular meshwork for laser trabeculoplasty • Minimize the risk of endothelial damage during iridotomy Contraindicaons

• Contraindicaon • Advanced corneal edema or opacificaon • Flat anterior chamber • Synechial angle closure • Complicaon: • mild iris • Corneal endothelial burn • Transient rise in IOP

Laser trabeculoplasty

• Relavely effecve,non-invasive. • Laser treatment to trabecular meshwork increase to increase oulow. Mechanism of acon

• Wise and Wier proposed that thermal energy produced by absorpon 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

• Eliminaon of some trabecular cells posrbeculoplasty.this smulate remaining cells to produce different composion of extracellular matrix with lesser oulow obstrucng properes. Laser trabeculoplasty

• Method • Argon laser trabeculoplasty • Selecve laser trabeculoplasty • Lens • Goldmann 3 mirror lens • Lana trabeculoplasty lens:

Argon laser trabeculoplasty

• Laser parameter • Power -300-1200mW • Spot size—50µm • Duraon -0.1 sec • Number of burns-30-50 spots evenly placed over 180deg. remaining in subsequent visit. Argon laser trabeculoplasty

• Ideally,spot should be applied Over schlemm’s canal avoding The iris root at the juncon of Anterior 1/3 to posterior 2/3 of Meshwork. • The energy level should be set To induce a reacon from a Slight transient blanching of The treated area to small Bubble formaon

Selecve 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 Selecve 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 frequency Nd:YAG 532nm

Spot size(µm) 50 400

Duraon 0.1s 3ns

Power 300–900 mW 0.6–1.2 mJ Degrees 180 180–360 Indicaons

• Chronic open angle glaucoma • Exfoliaon syndrome • Pigmentary glaucoma • Glaucoma in aphakia or pseudophakia Contraindicaons

• Closed or extremely narrow angles • Corneal edema • Aphakia with vitreous in ant.chamber • Vascular glaucoma • Acute uveis • Primary congenital glaucoma • Angle recession glaucoma Complicaons

• Most common risk is IOP spikes in about 3–5% of paents • Iris • Peripheral ant.synechiae • Hemorrhage • Corneal complicaon • 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 arion rate of 6–10% per year). • With SLT, IOP lowering occurs within 1–2 weeks; IOP lowering can connue for up to 4–6 months post-treatment and also connues for 3–5 years with a similar arion 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 selecve 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 • Duraon :0.1 second • spot size :100–200- µm. • This may restore the normal forward flow of aqueous, especially when accompanied by aggressive cycloplegic, mydriac, and hyperosmoc therapy • The Nd:YAG beam is directed at the anterior hyaloid face between the ciliary processes using a single burst at power sengs 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 Cyclophotocoagulaon

• Reduce aqueous producon by destrucon of ciliary epithelium • Techniques • Transscleral • Transpupillary • Endolaser • Indicaon • Failure of mulple filtering surgeries • Primary procedure to alleviate pain in neovascular glaucoma with poor visual potenal. • Painful blind eye • Surgery not appropriate Cyclophotocoagulaon

• Trans-scleral cyclophotocoagulaon • destroys ciliary epithelium and associated vasculature • decreased aqueous humor producon. • Nd:YAG laser – • good scleral penetraon • 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 absorpon by melanin. • So use of 50% less energy compared to the connuous wave Nd:YAG laser to achieve the same effect Cyclophotocoagulaon

— Trans-scleral Cyclophotocoagulaon • Noncontact Nd:YAG laser cyclophotocoagulaon • Contact Nd:YAG laser cyclophotocoagulaon • Semiconductor diode laser trans-scleral cyclophotocoagulaon • Endoscopic cyclophotocoagulaon

Cyclophotocoagulaon

• Noncontact Nd:YAG laser cyclophotocoagulaon • Nd:YAG laser is mounted on slit-lamp • 4–8 J/pulse, • duraon :20 ms • placed 1.0–1.5 mm posterior to the limbus total of 30–40 spots • 3 and 9 o’clock posions spared to avoid long posterior ciliary arteries • A contact lens may be used to blanch blood vessels to improve the focus • Atropine 1% and prednisolone acetate 1% are prescribed four mes a day; these are tapered as inflammaon subsides.

Cyclophotocoagulaon

• Contact Nd:YAG laser cyclophotocoagulaon • Nd:YAG laser in the connuous mode via a fiber opc system in direct contact with the conjuncva • The fiber opc laser probe is posioned perpendicularly on the conjuncva with the anterior edge 0.5–1.0 mm posterior to the surgical limbus. • power level of 4–9 W and duraon between 0.5 and 0.7 seconds Cyclophotocoagulaon

• Semiconductor diode laser trans-scleral cyclophotocoagulaon • most widely used method of ciliary ablaon 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 MicroPulse CycloPhotocoagulaon ENDOSCOPIC LASER CYCLOPHOTOCOAGULATION

ENDOSCOPIC LASER CYCLOPHOTOCOAGULATION

• Performed with an 810 nm diode laser • Xenon light source that provides illuminaon and a helium-neon laser aiming beam • starng sengs are 0.25 W with connuous exposure me. • The actual me of exposure is based on visual effect of ciliary process shrinkage and whitening • Typically, as much of the ciliary process is treated as possible, as there is a significant poron posteriorly that is usually not treated • cycloplegics are not necessary and steroids are used in the usual postoperave dosing Comparison Complicaons

• Conjuncval burn • Need for re-treatment • Hyphema • Loss of visual acuity • Inflammaon • Vitreous hemorrhage • Pain • Choroidal detachment • IOP spike • Phthisis • Cataract • Pupil abnormality • Hypotony CO2 Laser Assisted Sclerectomy Surgery • Similar to trabeculectomy

• Major difference being that aer the scleral flap is raised, the remaining sclera over the Schlemm’s canal and trabecular meshwork is dissected by the CO2 laser probe unl aqueous percolated over the enre dissected bed. • Aimed to prevent intra ocular complicaons. • Performed under sub-conjuncval anesthesia. CO2 Laser Assisted Sclerectomy Surgery Drawbacks

• Demands careful and delicate surgery • Relavely long learning curve • Can be performed only by highly skilled surgeons, Laser suture lysis

• Subconjuncval trabeculectomy flap sutures can be lysed with the laser postoperavely if there is inadequate filtraon • Dark nylon or proline sutures can usually be severed with the argon laser • sengs of 200–1000 mW for 0.02–0.15 second with a 50–100-µm spot size • feasible from about 3–15 days aer surgery or up to at least 2 months or more aer mitomycin-C use

Singh J, et al: Enhancement of post trabeculectome bleb formaon by laser suture lysis, Br J Ophthalmol 80:624, 1996. Method

Laser suture lens. The device has a small convex lens that compresses the edematous conjuncva perming a clear view of the ny nylon suture underneath the conjuncva. 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 ssues overlying the suture will absorb the energy, prevent treatment, and possibly cause conjuncval perforaon. • fluorescein-stained conjuncva limits argon laser energy transmission to the sutures and may cause conjuncval perforaon. • thick, inflamed Tenon’s capsule may also preclude successful LSL • Aer laser steroid is given to reduce external scarring • Addional suture can be lysed 1-2 days aer Reopening of failed filtraon site

• Filtering sites can close because of fibrosis on the external side • Membrane formaon or iris incarceraon on the internal side of the sclerostomy • Argon or Q-switched Nd:YAG laser can vaporize it With the argon laser, sengs 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 obstrucng 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

• Applicaons for the femto laser ab externo include • Creang trabeculectomy flaps, • Non-penetrang procedure flaps, • Near-perforang deep excisions under flaps, • Removal or thinning of trabecular meshwork and the inner wall of Schlemm’s canal, and creang 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 scleral windows for trabeculectomy • To create suprachoroidal fistulae. Cyclodialysis and laser

• Cyclodialysis cles have been both opened and closed with laser • Argon laser photocoagulaon using thermal burns of 0.1 second 100-µm spot size, and 500 mW can be used to close cyclodialysis cles and reduce hypotony • Nd:YAG is used to open cle.

Closure of a cyclodialysis cle. The beam is aimed deep into the cle to create an inflammatory response and generate closure. Postoperave 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 formaon of iridocorneal adhesions aer penetrang 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. Goniophotocoagulaon

• Use - anterior segment neovascularizaon • Goniophotocoagulaon 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, aer a while, as during the surgical procedure itself, the AC is le alone. • Goniopunctures are done with a YAG Laser • These help passage of aqueous into the scleral lake. • Blocked inner osum can be freed by Yag Laser, post trabeculectomy. • Vitriolysis , in case of a vitreous tag scking out, can be done using a YAG laser. • Modifying bleb by lasers aer staining the bleb with genon violet. Lasering the bleb

Goniopuncture Lasers in Glaucoma -Summarizing

• Lasers in glaucoma are an important part of the armamentarium in the management. • Several situaons exist when laser therapy may prove beneficial to the control of intraocular pressure, in associaon with medical therapy and may enhance quality of life by preserving visual funcon.