In the name of God

Glaucoma Drainage Devices

In the name of God

Glaucoma Drainage Devices S.M.Shahshahan M.DFeb 2010

HistoryEarly 20th Century

Use of foreign material

Setons or stents in the true sense

Silk thread, horse hair, gold, platinum, tantalum, glass, PMMA, silicone, gelfilm and acrylic The outcomes were generally poor

Glaucoma Drainage Devices, GDDsThe pioneering work by Molteno is the basis of all modern tube shunt implants.

Molteno revised his early tube design for a larger and more posteriorly fixated device.

Glaucoma Drainage Devices, GDDsA silicone tube and posterior encapsulation are common to all procedures.

Differences include use of flow restricting mechanisms, composition, shape and size.

Provide a free channel for aqueous outflow

Indications

NVG

Uveitis

ICE syndrome

Epithelial ingrowth

Indications (coun..)Severe anterior segment abnormalities

Failed Trabx

High risk for Trabx complications

Hx of bleb infections

Indications (coun...)Severe conj scarring

Aphakic and Pseudophakic

Intractable developmental glaucomas

With V-R procedures

Contact lens use

Filtration in GDDsThe filtration site is placed posteriorly near the equator

The episcleral explant stimulates fibrovascular proliferation (several weeks)

Silicone induces less inflammation than polypropylene

Filtration in GDDsLarger and thinner-walled capsules yield lower IOP

However there is an upper limit for bleb surface area

Very large blebs have great surface tension in the wall

Very large areas may be detrimental for bleb function and ocular motility

Glaucoma drainage devicesNon-restricted

MoltenoBaerveldt SchocketRestricted

AhmedKrupinJosephWhiteOptimedExPRESS

Valve mechanism propertiesOpening and closing pressures for valved shunts:10 and 8 mmHg for AGV 11 and 9 mmHg for Krupin

The AGV was the only valve shunt with variable resistance according to flow rate

Highest resistance with Optimed

Surgical technique

ANESTHESIA

GA or local

The choice depends on patients general and ocular conditions

Also dependent on surgeons experience and preference

Basic surgical stepsPeritomy (fornix or limbus based) MMC application ?Valve priming or tube ligaturePlate fixation (nonabsorbable material)#23 needle through limbus (1 to 2-mm intrascleral tunnel), parallel to iris Tube shortened obliquely About 2-3 mm is in the anterior chamber, bevel facing anteriorly Tube fixation with suture and coverage with patch graftConj closure

Choice of quadrantSite and quadrant of the operation depends on conj quality, implant size design and type , previous ocular procedures.

The S-N is best left avoided

Other quadrants each have their pros and cons

Beware of cosmesis in I-T shunts

Distance from optic nerve Greatest: Molteno Closest: AGVGenerally: 8-10mm posterior to limbus

Tube implantation siteAnterior chamber (routine)

Pars plana (PK, complete vitx, disorganized anterior segment)

Ciliary sulcus (extensive PAS, ACIOL)

Patch graftSclera, fascia lata, or pericardium. Risk of HIV transmission with sclera ? Pericardium is commercially prepared and packaged, sterility is superior to sclera.Other potentially acceptable tissues are amniotic membrane or dura.Cornea allows laser manipulation of sutures; may be superior cosmetically.All materials are comparable in terms of durability and melting.

Valved versus nonvalved GDDsAll valved shunts should be primed by irrigation of fluid through the tube.

Nonvalved devices need extra steps to prevent excessive filtration and hypotony

ADJUSTING TUBE FLOW4-0 nylon suture is inserted into the tube A 6-0 Vicryl suture is tied externally around the tube to allow controlled filtration.

An alternative approach is total occlusion of flow with the external ligature.

Venting foots are made in the tube proximal to the external ligature.

These vents are created with a sharp microblade and allow fluid flow at high intraocular pressures until the external ligature dissolves or is cut.

Two-stage approachThe plate is placed in the subconjunctival region and the tube is left in the subconjunctival space.

Anterior chamber entry is deferred until a later date.

After subconjunctival healing occurs, the tube is placed in the anterior chamber.

Postoperative medicationsTopical steroids

Cycloplegics

Antibiotic

Early Postoperative Complications

EARLY COMPLICATIONSElevated Intraocular Pressure

valve malfunction

tube occlusion

suprachoroidal hemorrhage

tube retraction

TUBE OCCLUSIONIris incarceration (cycloplegia, laser peripheral iridectomy or iridoplasty, surgical intervention)

Intraluminal fibrin or blood clot (observation, laser, tPA, irrigation)

Vitreous plugging (Nd:YAG laser vitreolysis or vitrectomy)

AQUEOUS MISDIRECTIONManagement as in other scenarios with malignant glaucoma

Redirection of the tube from the anterior chamber into the vitreal cavity through the pars plana

SUPRACHOROIDAL HEMORRHAGEA grave complication in high risk eyes

Risk factors and management as in other conditions

RETRACTED TUBEconfirm with gonioscopy. If the tube is too short, move the plate closer to the limbus or place an extender sleeve tube with a larger diameter over the preexisting tube to lengthen it. (tube extender commercially available for AGV)

LECTUER 03114476010 392