Glaucoma Drainage Devices S.M.Shahshahan M.D Feb 2010
Slide 4
History Early 20 th 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
Slide 5
Glaucoma Drainage Devices, GDDs The 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.
Slide 6
Glaucoma Drainage Devices, GDDs A 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 (coun..) Severe anterior segment abnormalities
Failed Trabx High risk for Trabx complications Hx of bleb
infections
Slide 9
Indications (coun...) Severe conj scarring Aphakic and
Pseudophakic Intractable developmental glaucomas With V-R
procedures Contact lens use
Slide 10
Filtration in GDDs The filtration site is placed posteriorly
near the equator The episcleral explant stimulates fibrovascular
proliferation (several weeks) Silicone induces less inflammation
than polypropylene
Slide 11
Filtration in GDDs Larger 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
Slide 12
Glaucoma drainage devices Non-restricted Molteno Baerveldt
Schocket Restricted Ahmed Krupin Joseph White Optimed ExPRESS
Slide 13
Valve mechanism properties Opening 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
Slide 14
Surgical technique
Slide 15
ANESTHESIA GA or local The choice depends on patient s general
and ocular conditions Also dependent on surgeon s experience and
preference
Slide 16
Basic surgical steps Peritomy (fornix or limbus based) MMC
application ? Valve priming or tube ligature Plate 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 graft Conj
closure
Slide 17
Slide 18
Choice of quadrant Site 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
Slide 19
Distance from optic nerve Greatest: Molteno Closest: AGV
Generally: 8-10mm posterior to limbus
Slide 20
Tube implantation site Anterior chamber (routine) Pars plana
(PK, complete vitx, disorganized anterior segment) Ciliary sulcus
(extensive PAS, ACIOL)
Slide 21
Patch graft Sclera, 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.
Slide 22
Valved versus nonvalved GDDs All valved shunts should be primed
by irrigation of fluid through the tube. Nonvalved devices need
extra steps to prevent excessive filtration and hypotony
Slide 23
ADJUSTING TUBE FLOW 4-0 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.
Slide 24
Two-stage approach The 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.
TUBE OCCLUSION Iris 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)
Slide 29
AQUEOUS MISDIRECTION Management as in other scenarios with
malignant glaucoma Redirection of the tube from the anterior
chamber into the vitreal cavity through the pars plana
Slide 30
SUPRACHOROIDAL HEMORRHAGE A grave complication in high risk
eyes Risk factors and management as in other conditions
Slide 31
RETRACTED TUBE confirm 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)