MIGS- glaucoma surgery advances

1. ADVANCES IN
GLAUCOMA
SURGERY - MIGS
DR. PRIYANKA RAJ

2. INTRODUCTION
• Trabeculectomy remains the 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 are required 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. Increasing Trabecular
Outflow

8. 1. Ab Interno Procedures

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 of the 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: iStent have 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 electrocautery device 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 blood reflux (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: Whitening of 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
• It is 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. Ab Externo

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 canal deroofed
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 high resolution 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-to mid-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 SCthe microcatheter
is withdrawn  SCE replaces the suture
stent

25. • Advantage:
 canaloplasty easy
 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. Subconjunctival
Implants

28. EX-PRESS Glaucoma Filtration Device
• 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 efficacy of 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
• flexible needle 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. Suprachoroidal
Shunts

33. • Principle:
• there is 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
• 6.35 mm 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% IOP reduction
• 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 device is 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
• the third 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 polypropylent curved 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 of a 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 operative techniques 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.