glaucoma, ophthalmology, drainage devices

1. Glaucoma Drainage
Devices
Dr. Meenank
M. S. Ophthalmology ( Post- Graduate)
ASRAM

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