2. Introduction
Glaucoma – Multifactorial progressive optic neuropathy
associated with visual field loss and characteristic structural
changes, including thinning of the retinal nerve fibre layer and
excavation of the optic nerve head
Elevated IOP is clearly the most frequent causative risk factor.
Choice of treatment is mainly
Medical Therapy
LASER Treatment
Filtering Surgeries
Choice of treatment in
Refractory Glaucoma's is
Glaucoma Drainage Devices
(GDD)
3. Glaucoma Drainage Devices
Glaucoma drainage devices create an alternate aqueous pathway from the
anterior chamber to the sub-conjunctival bleb or the supra-choroidal space
by channeling aqueous out through a tube
Drainage Devices
Setons (Bristle) - Refers to solid shaft prevents wound apposition
Stunt (Tubular structure) - Fluid passes passively
Valve - Tubular structure for unidirectional flow
Setons may be thread , wire , hair place in the wound to drain aq. Along side
the inserted material
Setons were unsuccessful as they were unable to maintain fistula patency
4. Indications
GDD were designed mainly to enhance trabeculectomy surgeries
Indication
Trab. With adjuvant therapy failed
Young patients
NVG, uveitic glaucoma, refractive pediatric glaucoma, glaucoma in
Aphakia, PPK, VRS, PRP
Sever conjunctival scarring
5. H i s t o r y
1912: The first translimbal glaucoma drainage device implanted by Zorab ;
device used silk thread to drain fluid
1969: Molteno announced that a large surface area is needed to disperse the aqueous beneath the conjunctiva.
He inserted a short acrylic tube attached to a thin acrylic plate. Most of the operations failed after the first 3-6
months because of plate exposure, tube erosion, and scar formation.
1976: First Molteno implant was introduced consisting of a long silicone tube attached to a large end plate
placed 9-10 mm posterior to the limbus .
The implant, which offered no resistance to the outflow, often resulted in hypotony , flat ACs , and choroidal
effusions.
1992: George Baerveldt discovered that increasing the surface area of the end plate(s) results in lower IOPs .
Baerveldt non-valved silicone tube attached to a large silicone plate with a surface area of 250 mm², 350 mm²,
500 mm²
1993: Ahmed glaucoma valve (AGV) introduced by Mateen Ahmed
1997: Introduction of the Helies drainage device which uses an artificial meshwork of PTFE fibers
1998: Glaucoma Drainage Devices have been implanted in 2,980 patients
2001: FDA approved the AquaFlow ™ Collagen Glaucoma Drainage Device as an alternative treatment for open-angle
glaucoma
6. Physiology
Basic design of drainage implant device shows
Fibrous capsule around effects the formation of bleb
Granulation leads to collagen capsule @ 1month and stable at
6mnth all over
Show microcystic spaces for aq. Drainage
Silicon tube from A.C
to disc/plate
Ridge- where tube is
inserted.
Dec. risk of obs. due
to fibrous capsule
Large surface area for
formation of bleb
7. Implants
Implants can be studied under
1. Type of plate
2. Type of material
3. Type of opening
Type of plate – of the available rigid and flexible plates the later
causes less inflammation
8. Type of material
Most commonly used materials are
Silicon
Baerveldt, Krupin, Ahmed
Polypropylene
Ahmed, Molteno
Hydroxylapatite
Expandable polytetrafluoroethylene
9. Medical grade silicone
Biocompatibility
Low tissue response to implantation
Odourless
Tasteless
Resistant to bacterial growth
Does not stain or corrode other materials
High tensile strength (1500psi), good elongation (to 1250%)
and flexibility
Temperature Resistant
Stable at a temperature range of 75-500oC
Chemical Resistant
Resists water, oxidizing chemicals, ammonia, and isopropyl
alcohol
10. Polypropylene
High flexibility and dimensional stability
Low thrombogenicity
Poor abrasion resistance
Non-toxic
High tensile and compression strength
Chemically resistant to most alkalis and acids, organic
solvents, degreasing agents, and electrolytic attack
Degrades in presence of UV light
11. Polytetrafluoroethylene or PTFE
Chemically inert to most chemicals including nitric, sulfuric,
and phosphoric acids
Hydrophobic
Highly crystalline and stable
Low friction
Low wear resistance
Inflammation caused by PTFE wear particles
12. Type of opening
Based on the type of opening implants can be classified into
1. Non- valved
Rely on resistance formed by fibrous capsule or bleb
Bleb grows around the implant and creates a space for fluid
to drain and be absorbed by surrounding tissue
Eg – Molteno, Baerveldt, Schocket
1. Valved
Only drains fluid at a certain IOP
Valve opens and fluid is drained into a reservoir where it is
absorbed by surrounding tissues
Eg – krupin, Ahmed
13. Non- valved devices
Baerveldt Implant
Plate features
barium impregnated
Large surface area – 250 mm², 350 mm²(less complication),
500mm²(not available)
Location
Superior- temporal quadrant under the sup. rectus muscle
inserted thgh one quadrant conjunctival insertion
Fenestration seen on the plate to allow fibrous capsule
formation and dec.ht. of bleb and diplopia
Indication – failed Trabeculectomy, cataract Sx
Side effects – restricted ocular movements @ 7yrs
Uncontrolled, complicated glaucoma
14. Molteno (1969)
Original design –
Single acrylic thin plate ( 13 mm diameter & 135 mm² S.A)
Silicon tube (outer-0.62 mm , inner-0.30 mm) connected to
upper end of plate
Thickened rim facilitating suturing to sclera adjacent to limbus
15. With subsequent modification came
Single plate
Moved to a position a few millimetres away from limbus to allow for better
drainage.
Aphakia, PPK, failed filters, NVG, < 3yr – 25% to 40%
Double plate
Inc. S.A. 270 mm,
Better control but inc. complication – hypotony
Dual chamber
In view to combat hypotony
Single implant ‘V’ shaped pressure ridge on upper surface of plate – inc. S.A. –
10.5mm
Molteno 3 ( 175mm² & 230 mm²)
Shows a bowel shaped structure on the implant plate at the tube opening
Acts a biological valve limiting aq. Flow during low aq. production
16. Schocket Tube
Anterior Chamber Tube Shunt To Encircling Band ( ACTSEB)
Contains a silastic tube used in nasolacrimal intubation encircling at
the equator under the rectus band
Show max IOP effect when coupled with krapin
17. Flow-Restricted Drainage Devices / Valved
Ahmed Glaucoma Valve (AGV)
Most commonly used valved implant
Implant design – silicon tube connected to silicon sheathed
valve held by a polypropylene body
Material Surface Area Type
Silicon
FP7 1.9mm² Single valve plate
FP8 96 mm² Small valve plate
FX1 180mm² 2 plates
Polypropylene
S2 189mm² Single valve plate
S3 96 mm² Small valve plate
B1 180mm² 2 plates
18. Valve related obstruction may cause hypertensive phase @ 4th – 8th P.O weeks
Hypertensive Phase : elevated IOP in the weeks to months after implantation as
a result of capsule formation around the implant plate. This is frequently termed
the hypertensive phase
Hypertensive phase is a result of holding the implant at no touch zone
No touch zone : area on the implant covering the silicon leaflet which when
grasped with forceps separated the valve from implant – definitive closure –
early P.O hypotony, fibro-vascular ingrowth b/w leaflet and implant failure
19. Krupin Implants (1976)
Krupin and associates developed a concept of a valve that opens at a
predetermined IOP to dec. early P.O. complication
Krupin Denver valve ( Original)
Internal supramid tube cemented to external silastic tube
Valve effect – by making a slit at closed ext. end of silastic which open opens at 9 – 10
mmHg IOP
Failure – no ext plate, and fibrosis eventually closed the valve
Krupin eye valve with disc
Longer version of Denver and attached to Schocket 180 implant which open at 10 – 12
mmHg IOP and valve @ in side the rim of plate
20. Other Drainage Devices
Ex-PRESS
Miniature non-valved device without an external plate
Made of rigid 316LVM stainless steel – same as cardiac stents
< 3mm long
Internal lumen size – 50μm/200μm
Biocompatible
Allows for the development of a delimited potential space and the
formation of a fibrous capsule to create the resistance to outflow
Implanted under a traditional trabeculectomy flap
21. The Solx Gold Shunt
Made from 24-karat gold and works to connect the anterior chamber and
suprachoroidal space
Pressure in the suprachoroidal space serves as a natural counter pressure to prevent
severe postoperative hypotony
Implanted by using an ab external approach so, no bleb
iStent trabecular microbypass stent
Stainless-steel stent with a lumen that is implanted from an ab interno approach
Traverses the trabecular meshwork and drains aqueous from the anterior chamber
into the Schlemms canal, enhancing aqueous drainage
22. SURGICAL TECHNIQUES
Basic Principal
1) Proper Traction – achieved by 6-0 vicryl / silk through superficial
cornea at superior limbus
2) Exposure Of Scleral Bed – a fornix based conjunctival flap is created
and elevated by a blunt dissection b/w tenons and episcleral with
blunt Westcott scissors exposing the scleral bed which is supported
by relaxing incision for surgical exposure
In case of large / double plate avoid superior-nasal ?
Can cause strabismus & close to optic nerve
3) Isolation Of Recti – muscle hooks are used to isolate the 2 recti on
either side of the surgical site
23. Implant
External implant is tucked under sub-tenons and sutured to sclera with 9-0 Proline
thgh the holes in the implant with the ant. Border 8-10 mm from limbus
2 stage implantation for non-valved
Ext plate is inserted sub-conj without inserting the tube, which is done 6-8 wks after
fibrous capsule formation
(Or)
Occluding the tube with ligature before inserting it and checking with BSS for occlusion
( prevents P.O hypotony)
Entering into A.C.
With hemostasis achieved a pracentisis ia done @ for placement of visco-elastic
Tube is cut beveled up and to a distance of 2-3cm into A.C
Closure
Autologous scleral graft of 5*7mm is used to cover the limbus and conjunctiva is
sutured followed by sub conj. Steroid and Antibiotic
24. COMPLICATIONS
Hypotony
m.c complication with non- valved in early P.O days until fibrous capsule
formation
Rx – temporary obs of lumen
Basic tech – suture ligation of tube
Valve implants
Hypotony + flat A.C – Inject visco elastic – observe for 24hrs – no
change – reposition device to prevent corneal decompensation
Late hypotony – Rx permenet occlusion of proximal tube and replacement
of implant
25. Elevated IOP ( early / late )
Early – Before the ligature around the suture dissolves – transient ↑ IOP
Rx – medically / combine trab. Without MMC to control IOP
htn phase (7 – 8 days ) –↓ IOP conj & corneal oedema, cong⁺ around implant
HTN phase – IOP ass with fibrous capsule formation and ↓ oedema – bleb formation
1 – 4 wks – bleb cong⁺ ↑IOP - cong⁺ ↓IOP – stabiles
↑IOP due to tube obs – fibrin, blood, iris, vitreous membranes, or silicone oil
Rx – reopening tube with – Iridectomy / NdYAG membrenctomy
Distal tube occlusion – scleral buckling
Rx – BSS irrigation / intra-cameral Tissue Plasminogen Activator to dissolve fibrin clot
26. Late ↑IOP
Seen with patent tube in thickened fibrous capsule
Rx – needle revision ;
complication – endophthalmitis
27. Migration, Extrusion, and Erosion
If not adequately secured
Migrate post. In to A.C – Rx)- reposition and re suture with 9-0 Proline
Ant Migration is due to dislocation
Extrusion – m.c in pediatric cases due to the development of eye ball
Can cause erosion of cornea
Avulsion – causes corneal melting and requires explantation of the implant
and possibly corneal grafting
Endophthalmitis
commonly seen after needling procedure
Cause – Propionibacterium acnes endophthalmitis
Rx – vancomycin (poor response)
Explantation with new devise instillation is a must
28. Corneal Decompensation
Related to the retrograde flow from the encapsulated reservoir to the
anterior chamber & Tube-cornea touch
Diplopia and Ocular Motility
devices with larger plates, implanted in the superonasal quadrant, can
interrupt extraocular muscle function and cause strabismus and diplopia
(exotropia, hypertropia, or limitation of ocular rotations )
Rx)- repositioning the device to superior-nasal
29. Other complication
Epidermal down growth
With tube inserted at limbus –
implant failure, corneal
decompensation
Sterile hypopyon
After removal of suture stents in
eyes with silicon oil
Irregular pupil
Root of iris adherent to tube
Globe penetration during
suturing
Cause – RD, Vit Hx
Retinal Complications
RD, choroidal effusion,
suprachoroidal Hx ( old age,
HTN, C. effusion, atherosclerosis)
Vision loss
Hypotony, shallow A.C., RD, Vit
Hx, CME
