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Glaucoma 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 GDDwere 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 st 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 Basicdesign 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 Implantscan 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 gradesilicone 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 orPTFE 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 subsequentmodification 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 relatedobstruction 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 SolxGold 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