Glaucoma drainage devices

Glaucoma drainage devices

1. GLAUCOMA DRAINAGE DEVICES Dr.M.Dinesh

2. Glaucoma drainage devices (GDDs) Principle work by creating an alternate pathway for aqueous outflow by channeling aqueous from AC through a tube of implant towards sub-conjunctival space or suprachoroidal space where it is absorbed into systemic circulation by diffusion and through scleral veins.

3. Drainage Devices Setons ( latin -Bristle) – Refers to solid (non hollow )shaft prevents wound apposition facilitating bulk flow by surface tension unsuccessful as they were unable to maintain fistula patency Sources of Seton: Silk, Horse hair, gold, Tantalum wire, platinum, gelatin , Silicon, PMMA. Stunt (Tubular structure) - a passive tubular structure incapable of influencing either antegrade or retrograde flow. Valve - Tubular structure for unidirectional flow

4. History 1907 :The first attempt to implant a drainage device was made by Rollet and Moreau , when they performed a double paracentesis and used horse hair through the corneal punctures to treat patients with painful absolute glaucoma. 1912: The first translimbal glaucoma drainage device implanted by Zorab ; device used silk thread to drain fluid 1969 : Molteno – 1 st scientifically explained the pathophysiology of bleb resistance and designed a tube.  All of the currently available GDD are based on fundamentals of Molteno implants . 

5. Molteno implants, offer no resistance to the outflow and post operative complications like hypotony, flat anterior chambers, and choroidal effusions were a frequent phenomemon . 1976 : Krupin developed a pressure sensitive, unidirectional valve that provides resistance to the flow of aqueous. 1992 : Baerveldt introduced a non- valved silicone tube attached to a large barium-impregnated silicone platen 1993 :Ahmed introduced the Ahmed glaucoma valve (AGV), a pressure sensitive unidirectional valve.   1997: Introduction of the Helies drainage device which uses an artificial meshwork of PTFE fibers 2001: FDA approved the AquaFlow ™ Collagen Glaucoma Drainage Device as an alternative treatment for openangle glaucoma

6. Implants can be studied under 1. Type of plate 2. Type of material 3. Type of opening 1. Type of plate – of the available rigid and flexible plates the later causes less inflammation

7. 2.Type of material Most commonly used materials are Silicon - Baerveldt , Krupin , Ahmed Polypropylene -Ahmed, Molteno Hydroxylapatite Expandable polytetrafluoroethylene

8. 3.Types of opening 1.GDDs with no resistance A)Non- valved /Non-restrictive implants / Open-Tube Drainage devices 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 Molteno Bareveldt Schocket Express miniature glaucoma shunt R 50 Istent from glaukos

9. B) Valved /Flow Restrictive implants:  Only drains fluid at a certain IOP Valve opens and fluid is drained into a reservoir where it is absorbed by surrounding tissues AGV Krupin slit valve Others Joseph , Optimed &White GDD 2.GDD with variable resistance:  Molteno dual ridge device Baerveldt bioseal (is a flap that overhangs the silicone tube as it opens on the endplate ) Deep light gold micro shunt from SOLX ( suprachoroidal shunt) Ref :35 Glaucoma drainage devices DOS times vol .13 issue no 8 Feb 2008

10. Indications : One or more filtering procedures that have failed Refractory infantile glaucoma Neovascular glaucoma Traumatic glaucoma Uveitic glaucoma Glaucoma in aphakia or pseudophakia Glaucoma following corneal transplantation Glaucoma with Penetrating keratoplasty Glaucoma with Retinal detachment surgery Glaucoma and aniridia Glaucoma and Sturge-Weber syndrome Glaucoma and ICE syndrome Glaucoma and contact lens dependence Glaucoma and epithelial ingrowth Glaucoma and severe surface disease (chemical burns, pemphigoid)

11. Contraindications: Eyes with severe scleral or sclera-limbal thinning Extensive fibrosis of conjunctiva Ciliary block glaucoma. Relative Contraindications: Vitreous in AC Intra-ocular silicone oil-Implant if required is placed in infero temporal quadrant

12. PHYSIOLOGY OF DRAINAGE IMPLANTS Basic design : consists of a silicone tube that extends from the anterior chamber (or, in some cases, the vitreous cavity) to a plate, disc, or encircling element beneath conjunctiva and Tenon capsule. The edge of the external plate has a ridge, through which the distal end of the tube inserts onto the upper surface of the plate. The ridge decreases the risk for obstruction of the posterior opening of the tube with the surrounding tissue and fibrous capsule. The plates of the glaucoma drainage devices have large surface areas and promote the formation of the filtering bleb posteriorly, near the equator.

13. Silicon tube from A.C to disc/plate Ridge- where tube is inserted. Dec. risk of obs. due to fibrous capsule plate,/disc

14. The mechanism by which drainage implant devices control the IOP relates to fibrous capsule that forms a filtering bleb around the external portion of the draining device and, the surface area of the implant plate.

15. After insertion, collagenous capsule forms around it Surrounded by a granulomatous reaction Reaction resolves in 4 months Capsule remains stable Matures over time, becomes thinner after 6 months Filtering bleb

16. The vast majority of glaucoma drainage devices develop an elevated IOP in the weeks to months after implantation as a result of capsule formation around the implant plate. This is termed as the hypertensive phase. The filtering bleb may fail after surgery due to the increased thickness of fibrous capsule around the drainage implant. Movement of the drainage plate against the scleral surface may be the mechanism of glaucoma implant failure resulting from the stimulation of the low-level wound healing response, increased collagen scar formation, and increased fibrous capsule thickness

17. 1.MOLTENO IMPLANT Original design – Single acrylic thin plate:13 mm diameter 135 mm² S.A Silicon tube connected to upper end of plate external diameter-0.62 mm internal diameter-0.30 mm Thickened rim which is perforated facilitating suturing to sclera

18. With subsequent modification came Single plate Double plate Dual chamber Molteno 3 a)Single plate Moved to a position a few millimetres away from limbus to allow for better drainage.

19. b)Double plate molteno implant : A double-plate Molteno implant combines two plates, one of which is attached to the silicone tube in the anterior chamber, a second tube connects the two plates, giving an increased surface area of 270 mm2 Better control but inc. complication – hypotony

20. c)Dual chamber : single-plate implant, in which a V-shaped “pressure ridge” is present on the upper surface of the plate In view to combat hypotony from over-filtration.

21. The V-chamber implant contains a thin V-shaped rim of polypropylene on the plate surface below the tube's entry, Encases an area of 10.5 mm2 around the opening of the silicone tube Since this V-shaped ridge is the same height as the circumferential rim of the plate, the weight of the overlying, hydrated Tenon's tissue will in theory collapse and form a temporary roof for the smaller V-chamber, thus limiting the extent of the bleb and filtration

22. d) Molteno 3 has a bowl shaped structure on the implant plate immediately at the opening tube. It is designed to function as a biologic valve by limiting the available area of filtration during times of low aqueous production.( limiting aq. Flow ) is available with plate sizes of 175 and 230mm2

23. 2 . Baerveldt implant : A silicone tube is attached to a silicone plate ( barium impregnated ) with a surface area of 250 mm2, 350 mm2 or 500 mm2. The Baerveldt plate has fenestrations that allow growth of fibrous tissue through the plate, serving to reduce the height of the bleb, which reduces the risk for diplopia and helps secure the implant.

24. The plate is typically positioned under the rectus muscle insertions, typically in the superotemporal quadrant A fibrous capsule forms after the first 3 to 6 postoperative weeks into which fluid can drain and from which fluid can be absorbed by the surrounding tissues.

25. 3.Schocket Tube Shunt Anterior Chamber Tube Shunt To Encircling Band ( ACTSEB ) A silicone or silastic tube is extended from the anterior chamber to a 360° encircling silicone band, as used in retinal detachment repair, which functioned in developing the reservoir for aqueous drainage.

26. Modifications: have included insertion of the tube into a band extending for only 90° beneath two recti muscles or into the preexisting encircling band in eyes with glaucoma after scleral buckling surgery

27. 4.Ex-PRESS Miniature non- valved device without an external plate Made of rigid 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

28. 5.Glaukos istent This is a light weight Titanium L-shaped device which is placed inside Schlemm's canal The heparin covered titanium is biocompatible, has thrombolytic activity and prevents stenosis.

29. A small, snorkel shaped tube, about 0.5 mm in length sits in the peripheral AC, allowing aqueous to bypass the inner wall of Schlemm's canal and the juxtacanalicular trabecular meshwork. The portion of the device that is placed inside the canal is 1 mm in length and is shaped like a half-pipe. It is designed to fit within the lumen of the Schlemm’s canal, with the curved convex side lying against the inner wall of Schlemm's canal. This avoids contact with the outer wall and the collector channel orifices that enter the outer wall. The three barbed ridges along this portion are designed to prevent loosening and provide a secure placement of the stent in the canal. These can either be right handed or left handed

30. Insertion : A temporal clear corneal incision is made, and the AC is filled with viscoelastic. An applicator grasps the device and under gonioscopic guidance, traverses the AC to reach the Schlemm's canal in the nasal quadrant. The pointed tip engages the trabecular meshwork and the stent is inserted in place.

31. Surgical procedure for implantation of the iStent

32. B) Valved /Flow Restrictive implants:  1.Ahmed Glaucoma Valve (AGV) Most commonly used valved implant Implant design – silicon tube connected to silicon sheathed valve held by a polypropylene body Mechanism : The aqueous is transported to the valve’s body, where it has to pass between two silicone elastomer foils, held in place by the polypropylene piece at a certain tension The initial pressure needed to break the adherence of these membranes often exceeds 100 mm Hg, but afterwards they separate whenever the pressure is over 12 mm Hg, and close when the pressure falls to 8 or less: this mechanism permits one-way flow only.

33. Ahmed valve’s three-piece design. F: Elastomer foils that regulate one-way flow. TC: Tapered chamber creates ventury flow towards the valve’s body. B: Body. E: Fixating Eyelets. AB: Assembly bolts help tighten the elastomer foils to the proper tension for flow regulation

34. Priming: Ahmed’s valve must be primed before use. A 27-gauge cannula is inserted 2 to 3 mm into the tube and BSS is injected until it separates the elastomer foils often a small “popping” sound is heard while the BSS separates the silicone foils.

35. Material Surface Area Type Silicon FP7 84mm² Single valve plate FP8 96 mm² Small valve plate FX1 180mm² 2 plates Polymethylmethacrylate Polypropylene S2 184mm² Single valve plate S3 96 mm² Small valve plate B1 180mm² 2 plates

36. Hypertensive phase : transient phase of low capsule permeability seen at 4 to 8 weeks postoperatively. “No-touch zone” on the Ahmed glaucoma valve: It is the area of the implant covering the chamber with the silicone leaflets. If the implant is grasped with forceps along the center line it may separate the valve cover from the implant. can cause a defect in closure of the valve - early postoperative hypotony and fibrovascular membrane ingrowth between the leaflets. lead to a failure of the valve due to adhesion of the valve membranes.

37. 2.Krupin Implant The original Krupin Denver valve was composed of an internal Supramid tube cemented to an external silastic tube The valve effect was created by making slits in the closed external end of the silastic tube, designed to open at an IOP between 9 and 11 mm Hg. Failure The tube was short extending only a few mm subconjunctivally , no external plate. Fibrosis eventually closed the subconjunctival portion of the valved tube

38. Modifications: Krupin eye valve with disc a long Krupin -Denver drainage tube with the one way valve design was attached to a 180o Schocket type scleral explant In the newer design of the Krupin implant, the valve lies inside the rim of the plate at its insertion and is exposed directly to the sub conjunctival tissues

39. 2. GDD with variable resistance:  Gold micro-shunt The deep light glaucoma treatment system includes a titanium sapphire laser and a photo titratable gold micro shunt. The laser emits microsecond infrared light pulses that passes through the trabecular meshwork tissues, producing significant opening of the trabecular meshwork, allowing increased aqueous outflow. The gold shunt is biocompatible and inert, made of 99.5 percent pure gold. It is a flat plate 5.2 mm long, 2 mm wide and 60 thick, containing multiple microchannels.

40. Initially, half of these microchannels are open and the remainder closed by a thin film of gold which can be opened after implantation, using the titanium sapphire laser. This reactivates the shunt's effect and additional drop in IOP can be obtained. This phototitration can be done at any time postoperatively. The shunt is implanted through a 3 mm clear corneal incision made at the limbus into the suprachoroidal space using a preloaded insertion device. The channels in the shunt form a bridge between the anterior chamber and suprachoroidal space

41. Surgical Procedure- Basic Principles Tractional suture :A 6-0 Vicryl or silk traction suture is placed through superficial cornea near the superior limbus and attached to the drape beneath the eye. Conjunctival flap :A fornix-based conjunctival-Tenon capsule flap is created, usually in the superotemporal quadrant, to expose the scleral bed. The flap is slightly elevated to allow for blunt dissection between Tenon and episclera with blunt Westcott scissors.

42. Isolation of recti :A muscle hook is then used to isolate the two rectus muscles on either side of the surgical site. Placement of implant :The external plate is then tucked posteriorly into the sub-Tenon space and is sutured to sclera with nonabsorbable 9-0 Prolene or nylon sutures through the anterior positional holes of the plate,with the anterior border at 8 to 10 mm posterior to the limbus. The tube is then cut, bevel up, to permit its extension 2 to 3 mm into the anterior chamber

43. Before the tube is inserted into the anterior chamber, a limbal area is cauterized to prevent bleeding from the insertion. Entering into AC :The anterior chamber is then entered through the cauterized limbal area with a 23-gauge or a 22-gauge needle, parallel to the iris plane . The needle creates a watertight seal, preventing leakage around the tube and thus reducing the risk for postoperative hypotony

44. Insertion of the tube :The tube is then inserted into the anterior chamber via the needle track.The tube can be secured to the sclera by using a nonabsorbable suture, Patch graft :The tube may occasionally erode through both sclera and overlying conjunctiva at the limbus. To avoid this potential complication, a rectangle of preserved donor tissue of approximately 5 mm × 7 mm over the tube at the limbus.

45. Processed pericardium ( Tutoplast ), donor sclera, dura, and fascia lata are available commercially for this purpose. It is also possible to use autologous sclera or to place the tube under a partial-thickness scleral flap Closure :The conjunctiva is then sutured back to its original position using Vicryl sutures. Subconjunctival steroids and antibiotics are injected at the completion of the procedure in a quadrant away from the surgical site.

46. Non- valved GDD: To avoid post-operative hypotony, a two stage implantation procedure can be adopted. The tube is inserted 6-8 weeks following the positioning of the external plate allowing the formation of a fibrous capsule around the plate prior to the insertion of the tube into the AC . A more commonly used method consists of occlusion of the tube lumen with an absorbable suture like vicryl .

47. Complications Intraoperative Complications a. Bleeding Occurs typically in neovascular glaucoma Large hyphemas must be evacuated as they can block the tube.

48. b. Misdirection of the silicone tube into the posterior chamber may occur in the presence of peripheral anterior synechiae. c. Loss of Aq may occur if the port size is bigger than tube. This can be remedied by introduction of saline or viscoelastic through a previously placed paracentesis opening and choosing 23 or 24 gauge needle.

49. Early Postoperative Complications a. Hypotony with or without associated choroidal effusions. Small effusions may be left to resolve spontaneously. Large effusions resulting in kissing choroids may have to be evacuated. Hypotony is best treated by prevention, either by the use of valved implants or by occlusion of the silicone tube with a stent and/or a constricting ligature.

50. b. Increased IOP may occur due to occlusion of the silicone tube: The opening of the tube may be obstructed by iris - can be treated by YAG ablation of the iris tissue. Occlusion by vitreous in aphakes can occur - can be prevented by thorough vitrectomy prior to tube insertion.

51. c.Corneal Decompensation: may be due to the retrograde flow from the encapsulated reservoir to the anterior chamber. Tube-cornea touch is another cause of corneal decompensation .

52. d. Early postop endophthalmitis is a rare complication. It can be treated by immediate removal of the implant and surgical management of the infection, with subsequent placement of a new implant.

53. Late Complications Encysted bleb can form. Deflation of the bleb to allow compressed channels in the wall of the bleb to expand and reestablish drainage may be necessary. Encysted blebs contain a relatively large amount of aqueous and as much as 1 cm3 of aqueous may be withdrawn to deflate the bleb with no loss of anterior chamber. Also as these blebs are relatively avascular , needling them is less traumatic. A regimen consisting of diclofenac 75 mg daily,prednisolone 40 mg daily and topical corticosteroids may be helpful if given not later than 14 days postoperatively and continued for at least six weeks.

54. b. Erosion of the silicone tube through the sclera or scleral patch and conjunctiva may occur. c. Plate migration may occur if the body is not fixed properly. If the plate migrates towards the medial rectus muscle insertion, myositis may develop. It resolves after implant removal

55. d. Limitation of eye movements can occur specially when placed in upper nasal quadrant. The movement most commonly affected is upgaze . Other patterns are exotropia, hypertropia and, limitations of ocular rotations. Placement of the implants in the lower fornix restricts downgaze with associated diplopia .

56. e. Endophthalmitis : Exposure seems to be the most important risk factor for these infections. Surgical revision with a patch graft is indicated in all these cases to prevent endophthalmitis .

57. Other possible complications are • Epithelial downgrowth: It can cause implant failure, corneal decompensation, and formation of a true Tenon's cyst. • Epithelial invasion into the fibrous capsule with persistent aqueous leak. • Sterile hypopyon . • Irregular pupil many years later due to adherence of the iris root to the tube. • Globe perforation while suturing the plate to the sclera causing retinal detachment or vitreous hemorrhage.This is seen more commonly in high myopes with thin sclera. • Retinal complications include RD,suprachoroidal hemorrhage, vitreous hemorrhage,choroidal effusion.

58. Outcomes Long term studies revealed success rates 65 to 85% in achieving IOP control. Molteno implants, in general, lower IOP more than Ahmed implants but have higher risk of complications and need for resurgery . Success is lower in pediatric glaucomas , with failure rates of more than 30%, and most of them requiring other surgeries. Drainage devices have been particularly successful in neovascular glaucoma (success rates 62% at 1 yr but diminished with time).

59. Tube vs trabeculectomy (TVT) study Multicenter RCT comparing tube(350 sq.mm Baerveldt implant) shunts with trabeculectomy with mitomycin-C(MMC) in eyes with previous cataract and/failed glaucoma surgery. 1 st year of follow-up, the tube patients were more likely to maintain IOP and avoid hypotony or loss of light perception or resurgery as compared to trabeculectomy patients. However tube patients needed more supplemental therapy. 5 yrs of follow-up, IOP control was found to be similar in both groups but the trabeculectomy group needed additional surgery more than the tube group .

60. The Hydrus Microstent : trabecular bypass device and Schlemm’s canal scaffold nitinol, an alloy of nickel and titanium. 8-mm-long crescent with an open posterior surface and three windows in the anterior surface designed to be inserted through trabecular meshwork and to follow the curve of Schlemm’s canal. The length, being larger than the iStent , is such that three clock hours of Schlemm’s canal can be cannulated, increasing the likelihood of accessing multiple collector channels, as well as dilating the canal and preventing canal compression.

61. THAN Q Ref : Shields textbook of glaucoma 6 th ed Journal of Clinical Ophthalmology and Research - May-Aug 2013 - Volume 1 -Issue 2 Glaucoma drainage devices DOS times Feb 2008 vol .13 issue no 8 Aqueous Drainage Devices V. Velayutham MS Atlas of Glaucoma Surgery Tarek Shaarawy MD André Mermoud MD P ubmed The New Era of Glaucoma Micro-stent Surgery dec 2016vol 5 issue 2

62. The Cypass : a fenestrated polyamide tube 6.35 mm in length, with a 300-mm lumen designed to be implanted ab interno and inserted between the ciliary body and the sclera. It provides a direct communication between the anterior chamber and suprachoroidal space.

63. The XEN GEL Implant is a 6-mm cylinder of collagen-derived gelatin cross-linked with glutaraldehyde, making it permanent and non-degrading, with no foreign body reaction. It comes pre-loaded in the injector and is implanted ab interno , creating a drainage pathway between the anterior chamber and subconjunctival space. The procedure is often augmented with subconjunctival injection of mitomycin-C. 

64. OptiMed Glaucoma Pressure Regulator It is made of a silicone tube with a PMMA matrix plate. The inner diameter of the tube is 0.38 mm and outer diameter is 0.76 mm. A 5 mm PMMA tube is inserted into the silicone base with dimensions of 1×2×3×4 mm. The base contains 180 to 200 microtubules through which aqueous percolates through to the subconjunctival space. Aqueous outflow happens when the pressure within the eye exceeds 10 mmHg. Capillary action draws fluid through the matrix as IOP increases. The pressure gradient across the PMMA microtubules is governed by Poiseuille's formula.

65. Susanna Glaucoma Implant This has a reservoir body conforming to the shape of the globe at its equator and a ridge in the end plate to protect the inner opening of the silicone tube from blockage by fibrous tissue growth. A fenestrating end plate promotes fibrous tissue anchoring, resulting in less micromotion that may cause more inflammation decreasing the permeability of the capsule. The foot plates measuring 4 mm in length allow easy fixation at 6mm from the limbus and yet allowing the plate to be placed at 10 mm from the limbus, reducing the likelihood of its extrusion.

66. 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

67. 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

68. 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

69. Implants for non penetrating deep sclerectomy Absorbable implants 1. Aquaflow - Collagen implant 2. SK gel 3.5 & 4.5 implant- Reticulated Sodium Hyaluronate 3. Healon GV Non Absorbable implants 1. TFLUX implant. T- shaped implant made of polymagma . 2. TBAR- Made of surgical grade Stainless steel 3. MERMOUD X- Essentially a PMMA implant. 4. Mehta hema wedg

70. 4.Ex-press shunt The Ex-PRESS mini-glaucoma shunt is a 400 μm wide × 3 mm long, stainless steel device. It has a beveled, sharpened rounded tip, a disc like flange (<1 mm2) at the proximal end and a spur like projection that prevents its extrusion. The external flange and inner spur are angled to conform to the anatomy of the sclera, and the distance between them corresponds to the scleral thickness at the site of implantation. The inner diameter of the silicone tube is 125 μm and the outer diameter is 250 μm , making the tube narrow enough to fit the lumen of the Schlemm canal.

71. The implant is sterilized by gamma radiation and is a single-use device that should be stored at a temperature between 15°C and 30°C. The bleb formation starts immediately and microcysts within the bleb can be seen within the first or second post-operative day.

72. After insertion of the drainage device, a thin collagenous capsule, surrounded by a granulomatous reaction, is present at 1 month. The granulomatous reaction resolves after 4 months, capsule thickness remains relatively stable , and the collagen stroma becomes less compact. The fibrous capsule matures over time the capsule functions by a passive mechanism, shunting the flow of aqueous humor to the surrounding orbital tissues . All surfaces of the fibrous capsule contribute to filtration.