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ADVANCES IN GLAUCOMA SURGERY - MIGS
- 1. ADVANCES IN GLAUCOMA SURGERY -MIGS DR. PRIYANKA RAJ
- 2. INTRODUCTION • Trabeculectomy remainsthe standard surgical procedure for achieving control of intra-ocular pressure (IOP) in medically uncontrolled glaucoma patients, with or without anti-fibrotic augmentation. • Recently, glaucoma drainage devices have gained considerable mileage and popularity in both high risk as well as primary glaucoma cases. • Complications- accelerated cataract formation wound leak Hyphaema late bleb leak bleb encapsulation corneal decompensation bleb-related endophthalmitis tube-related complications (with drainage devices).
- 3. Micro-invasive Glaucoma Surgery(MIGS) • Group of glaucoma surgeries that share 5 preferred qualities 1. An ab-interno micro-incisional approach contrary to conventional trabeculectomy, which is an ab-externo procedure. MIGS through a clear corneal incision spare the conjunctiva. They allow direct visualization of internal anatomical landmarks and can be combined with cataract surgery also. They also allow maintenance of the anterior chamber by virtue of being micro incisional, along with causing little anatomical distortion, refractive change and hence, have increased safety. 2. cause minimal trauma to the target tissue, anatomically and physiologically. exhibit a high degree of biocompatibililty. 3. The surgical procedure shows at least a modest efficacy initially.
- 4. 4. They arerequired to have a high safety profile and avoid the serious complications seen with conventional surgical procedures. 5. The procedure has rapid recovery and should minimally impact the patients’ quality of life. Ease of use and a steep learning curve are also desirable features in MIGS.
- 5. MEACHANISM OF ACTION 1.INCREASE OUTFLOW by creating a new drainage channel into the subconjunctival space by forming an external bleb such as Ex-PRESS glaucoma implant, Fugo blade transciliary filtration 2. INCREASE THE CONVENTIONAL TRABECULAR OUTFLOW into the Schlemm’s canal as with trabecular micro-bypass stent (Glaucos iStent), trabectome, Excimer laser trabeculotomy (ELT), canaloplasty and Fugo Blade goniotomy 3. INCREASE THE UVEOSCLERAL OUTFLOW into the suprachoroidal space (CyPass Shunt, SOLX Gold shunt).
- 7.
- 8. 1. Ab InternoProcedures
- 9. Glaukos iStent ® •1 x 0.3 mm heparin coated titanium implant • Inserted through the trabecular meshwork (TM) into Schlemm’s canal (SC) • FIRST FDA approved trabecular bypass stent • Indications: in conjunction with cataract surgery for the reduction of intraocular pressure (IOP) in adult patients with mild-to-moderate open- angle glaucoma currently treated with ocular hypotensive medication. • L-shaped device + pointed tip penetrates the TM+ 1 mm long trough that rests in the Schlemm’s canal + “snorkel” that faces the anterior chamber • implanted with the use of a disposable inserter via gonioscopic guided approach from a paracentesis site. • Multiple iStents can also be implanted at once and have shown good efficacy (Syney Trial)
- 10. ADVANTAGE • maintenance ofthe bypass patency by virtue of its heparin coating. COMPLICATIONS 1. mild hyphaema from the Schlemm’s canal 2. transient IOP spike 3. corneal edema 4. stent malposition 5. lumen obstruction by blood clot or iris 6. inability to implant the stent 7. vitreous incarceration 8. need for second surgery.
- 11. • EFFICACY: iStenthave shown greater number of subjects achieving ≥20% IOP reduction with iStent combined with cataract extraction versus cataract surgery alone in patients of open angle glaucoma. • 2nd generation iStent iStent inject conical design. • 3rd generation iStent iStent Supra developed for placement in the suprachoroidal space.
- 12. Trabectome • 19.5-gauge electrocauterydevice with a disposable hand piece connected to a console, with irrigation and aspiration controlled by a foot pedal. • Under gonioscopic guidance, 90 -120 degrees of the trabecular meshwork and inner walls of schlemm’s canal is cauterised and stripped to create a direct communication between the anterior chamber of the eye and Schlemm’s canal. • Studies have reported significant IOP reduction with Trabectome similar to trabeculectomy either alone or in combination with phacoemulsification in open angle glaucoma
- 13. COMPLICATIONS: 1. Intraoperative bloodreflux (100%) 2. goniosynechiae formation 3. membrane growth • IOP levels achieved: in range of low to mid-teens mean reduction approximating 30% over a 6-month follow up Note: the higher the IOP was before surgery, the greater the IOP reduction. FDA approved (2004) lead to IOP elevation
- 14. Excimer Laser Trabeculotomy •utilizes the energy of a XeCl pulsed excimer laser (308 nm wavelength) connected to a quartz fiber-optic probe. • Creats multiple microperforations in the TM and inner wall of SC to increase aqueous outflow. • The probe tip is bevelled at 65 degrees to aid the placement of the tip against the angle. 8- 10 laser punctures spaced 500µ apart over 90 degrees are created under gonioscopic or endoscopic visualizaton • It delivers a mean energy of 1.2 mJ over 80 ns duration with each pulse.
- 15. • END-POINT: Whiteningof the TM followed by blood reflux from the laser site following laser ablation • The lack of circumferential flow in the SC may limit its efficacy, as well as the theoretical possibility of closure of these microholes. • NOT yet approved by FDA • IOP decrease of 38.6% after 5 years, higher reduction when combined with cataract surgery
- 17. Hydrus Microstent • Itis an “intracanalicular scaffold” • 8 mm long device • made of a highly elastic biocompatible material called nitinol • 3 windows along its length and is open on its posterior surface • It is inserted into Schlemms canal across the TM during cataract surgery • proximal 1mm inlet of the microstent left outside the SC, facing the anterior chamber to bypass the TM.
- 18. • Intracanalicular stent,dilating approximately one quadrant of the SC increases aqueous outflow from the anterior chamber to SC by bypassing the TM and by dilating the canal • INDICATIONS: mild to moderate glaucoma in conjunction with cataract surgery • FDA approved (2018) • HORIZON trial • the device reduced IOP by 7.5 mmHg, approximately 2.3 mmHg more than the cataract surgery-only group • COMPLICATIONS: 1. device obstruction 2. worsening of visual field mean deviation by 2 dB or more 3. BCVA loss of more than 2 ETDRS lines
- 19.
- 20. Canaloplasty • Non-penetrating +bleb-independent procedure • Aqueous outflow is enhanced by circumferential 360 distention of the Schlemm’s canal done with viscous material like Healon GV through a microcatheter. • Also establishes circumferential flow within the SC and stretches the TM. • The microcatheter is 200 µm in diameter and has an optical fibre illuminated beacon tip to assist in guidance
- 21. • Schlemm’s canalderoofed trabeculo-descemetic window created microcatheter advanced into the Schlemm’s canal full length of the canal is visco-dilated 10-0 polypropylene suture is sutured to the distal tip of the microcatheter and looped through the canal suture is then tightened to ensure that it stretches the Schlemm’s canal and TM circumferentially.
- 22. • Intraoperative highresolution ultra-biomicroscopy can confirm the placement of this suture. • US-FDA approved • CONS: technically more difficult Expensive time-consuming procedure efficacy is limited by the resistance of SC and episcleral venous pressure. • Complications 1. hyphema 2. elevated IOP 3. descemet’s detachment 4. conjunctival scarring 5. bleb formation
- 23. IOP reduction: alone:lower-tomid-teens combined with cataract surgery 30-65% # Phacoemulsification combined with canaloplasty gives superior results over canaloplasty alone.
- 24. Stegmann Canal Expander •9.0 mm long • made of polyimide • placed into Schlemm’s canal • creates a permanent distension of the TM. • Each stent occupies one quadrant of the SC circumference. • Due to its fenestrated nature SCE is patent to aqueous humor. • placed in a similar fashion as canaloplasty. • viscodilation of the SCthe microcatheter is withdrawn SCE replaces the suture stent
- 25. • Advantage: canaloplastyeasy no ‘cheesewiring’ of the suture under tension. • The superficial scleral flap is sutured very tightly as in canaloplasty to prevent bleb formation and to force the aqueous humour leaving through the physiological drainage system. • Complications: 1. descemet’s tear 2. postoperative IOP spike 3. Hyphema 4. iris prolapse
- 27.
- 28. EX-PRESS Glaucoma FiltrationDevice • It is a small, stainless steel implant less than 3 mm in size which diverts aqueous from the anterior chamber into the subconjunctival space similar to a conventional trabeculectomy • inner diameter of 50 μm for providing non-valved restricted aqueous outflow. • inserted under a partial thickness scleral flap using its device inserter, after making an opening into the anterior chamber under the scleral flap with a 25-27 gauge needle (400 microns outer diameter).
- 29. • IOP-lowering efficacyof ExPRESS shunt as compared to conv entional trabeculectomy (39.9%–46.6%). • INDICATION: patients who have uncontrolled glaucoma, including those who have failed prior medical and conventional surgical treatments. • Those patients who have very narrow angles, neovascular glaucoma, uveitis or severe dry eye are not good candidates for this implant. The higher cost of this implant is a matter of consideration when deciding for primary Ex- PRESS implant insertion.
- 30. AqueSys XEN implant •soft flexible hydrophilic gelatin tube • inner diameter of 65 microns. • It is placed via ab interno into the subconjunctival space, where it hydrates and swells in place, thus preventing migration. • The idea is to create a subconjunctival filtration bleb without opening the conjunctiva. • There is no published data yet about the device.
- 31. InnFocus Microshunt • flexibleneedle like tube • made of a highly biocompatible material SIBS, with fins halfway across its length to act as stopper to minimize aqueous leakage and to prevent internal migration of the tube. • The internal diameter of this tube is 70 μm. • inserted using the ab-externo approach through a small scleral pocket into the anterior chamber, making a thin needle tract.
- 32.
- 33. • Principle: • thereis a pressure gradient of 1-5 mmHg between the anterior chamber and the suprachoroidal space, the pressure in suprachoroidal space being lower creates a unidirectional flow towards the suprachoroidal space. • Various suprachoroidal shunts have been developed and are undergoing trail for efficacy for favourable results.
- 34. CyPass micro-shunt • 6.35mm fenestrated tubular shunt with an external diameter of 510 microns, made of polyimide • designed for use with cataract surgery. • inserted into the suprachoroidal space and promotes aqueous outflow across the uveoscleral pathway. • It is inserted via transcameral over a guidewire with a special tip that disinserts the ciliary body from the scleral spur to create a controlled cyclodialysis, and the device is then inserted in the cleft created.
- 35. • 30-35% IOPreduction • Complications: 1. Transient hyphema 2. hypotony 3. postoperative inflammation 4. Endothelial cell loss • 26-37% IOP reduction. (>80% patients) • FDA approved (2016) recalled in 2019
- 36. SOLX Gold Microshunt •gold has excellent biocompatibililty and inertness in the human eye. • It is a nonvalved flat plate drainage device, made of 24-karat medical-grade gold • measuring 3.2 mm x 5.2 mm x 44 µm thick, weighing 6.2 mg, composed of two leaflets joined together vertically • inserted into the suprachoroidal space to shunt aqueous from the anterior chamber. • It includes 19 microchannels (10 closed, 9 open) for aqueous to percolate • can be opened more with laser energy after surgery, if a further IOP decrease is desired.
- 37. • The deviceis positioned through a fornix-based conjunctival flap and under a 4 mm full-thickness scleral dissection into the created suprachoroidal space by ab-externo route. • MODEST IOP lowering • Complications: 1. transient hyphema 2. Choroidal detachment 3. corneal edema due to endothelial-shunt 4. over-filtration causing exudative retinal detachment • HIGH FAILURE rate: formation of a thin inflammatory membrane obstructing the anterior holes
- 38. iStent Supra • thethird generation Glaukos device for ab-interno implantation into the suprachoroidal space in both phakic and pseudophakic eyes. It has a lumen of 0.16-0.17 microns, made of heparin-coated polyethersulfone and a titanium sleeve.
- 39. Aquashunt • a polypropylentcurved device with a tapering edge, implanted ab-externally that has a single large lumen as compared to multiple small channels in SOLX Gold microshunt. • full thickness scleral incision expose the suprachoroidal space. The shunt is advanced through the suprachoroidal space using a custom inserter, breaking attachments between the ciliary body and the scleral spur to enter the anterior chamber. • The distal end of the device is tucked underneath the sclera, posterior to the scleral incision and the device is sutured to the sclera in order to secure its position.
- 40. STARflo • made ofa sheet of porous silicon material (STAR) with an anvil-like head to prevent its extrusion, placed in suprachoroidal space via ab-externo approach (partial thickness scleral flap). • The head is implanted in the anterior chamber at the anterior aspect of the scleral flap, and a full thickness scleral incision is made at the posterior edge of the flap to allow the body to be inserted into the suprachoroidal space. • The scleral and conjunctival flaps are sutured tightly to avoid leakage of aqueous and bleb formation. • Early postoperative complications included bleb formation, hypotony, choroidal hemorrhage
- 41. CONCLUSION • Current operativetechniques for ab-interno MIGS require direct gonioscopy, intraoperative manipulation of microscope and patient head tilting. Better intraoperative surgical techniques may reduce the existing complications with these newer procedures. • Most of the existing studies have used these devices in conjunction with cataract surgery. • The efficacy of most microinvasive devices is modest in comparison to trabeculectomy or glaucoma drainage devices, but their advantage over these invasive surgeries lie in their better safety profiles. • Hence they are best suited for early to moderate, uncomplicated glaucoma cases, and not for advanced glaucomatous damage where IOP requirement is in low teens.