Diamond Y. Tam
Physiologic aqueous outflow pathways include the conventional outflow
pathway and the uveoscleral outflow.
Whereas surgical procedures such as canaloplasty and trabecular bypass
stents aim to enhance conventional outflow, new devices such as the Gold
Micro-Shunt implant (Solx) augment aqueous outflow into the suprachoroidal
space from the anterior chamber.
Two models — the GMS and the GMS Plus — differ in size and
width of the drainage channels, with the latter being larger. The shunt
consists of two leaflets fused together, vertically concealing channels in the
body of the device that connect the anterior openings to the posterior
openings. The width of the channels in both models is 25 µm. However, the
height of the channels in the GMS model is 44 µm compared with 68
µm in the GMS Plus.
Insertion of the shunt begins with a fornix-based conjunctival peritomy
of about 4 mm in the area of intended shunt placement with an anterior lip of
conjunctiva left behind. A horizontal scleral incision of about 3.5 mm is then
fashioned, usually 2 mm from the limbus, and carried out to a near
full-thickness depth, where the blue hue of choroid is visible through a thin
layer of sclera.
This incision may need to be more posterior in highly myopic eyes or
eyes with large anterior segments. Intraoperative gonioscopy can also be useful
to assist in ascertaining that the incision is created at the appropriate
distance from the limbus.
|A 95% thickness scleral cut-down is created after a
conjunctival peritomy to set the depth for the scleral tunnel
|A scleral tunnel incision is created
forward to fashion the pocket in which the shunt will sit.
|A full thickness incision has been made,
and choroid is visible at the posterior edge of the scleral tunnel
|Gonioscopy is a helpful adjunct during
surgery to assess the position of the shunt in the anterior
|A postoperative slit-lamp photograph of a
patient with the shunt visible. Note also the failed subconjunctival filter
|A postoperative photograph using a
gonioscopy lens to view the shunt.
Images: Tam DY, Ahmed
A deep 95% thickness scleral tunnel is carried forward until the scleral
spur is then performed without entering the anterior chamber. A separate
corneal paracentesis incision should then be made to decompress the eye. The
remaining thin layer of sclera overlying the choroid at the base of the initial
incision is then cut, exposing the choroid.
A minute volume of suprachoroidal lidocaine should then be carefully
administered with a blunt cannula posteriorly, along with a small volume of
suprachoroidal viscoelastic. Through the previously created paracentesis
incision, the anterior chamber is formed with viscoelastic, most importantly in
the area of the anticipated shunt placement.
A horizontal entry is then made into the anterior chamber at the level
of the scleral spur through the previously created scleral tunnel incision. The
shunt is then brought onto the field and positioned in the scleral pocket
Pushing the implant forward so the posterior edge clears the scleral
incision and then tucking the posterior edge into the suprachoroidal space
enables correct positioning. The anterior aspect of the shunt should be
positioned in the anterior chamber while the posterior aspect rests in the
suprachoroidal space posteriorly.
A 27-gauge needle or Sinskey hook may be used to manipulate the shunt
both externally and through the anterior chamber to achieve the desired
The anterior aspect of the shunt is crescent-shaped with a positioning
hole in which a Sinskey hook can be placed to assist with positioning. With an
intraoperative gonioscopy lens, the anterior drainage openings should be
visible and clear of angle structures. The posterior drainage openings should
also not be visible externally and completely located in the suprachoroidal
Once satisfactory position has been achieved, the scleral incision
should be closed in a watertight fashion using interrupted 10-0 nylon sutures,
typically four or five sutures. The conjunctiva is then closed with a running
horizontal mattress suture using 10-0 Vicryl suture with a vasectomy needle,
again in a watertight fashion.
Early results promising
The Gold Micro-Shunt is a new device designed to enhance uveoscleral
outflow by providing a conduit for aqueous to exit the anterior chamber,
through the shunt and into the suprachoroidal space.
Early experience appears to show a high safety profile with reasonable
efficacy. Data that have been released by Solx in patients with at least one
prior failed incisional glaucoma procedure showed a 33% reduction in IOP at
1-year follow-up of 39 patients who received the GMS model with a preoperative
IOP of 27.4 ± 4.7 mm Hg as compared with 18.1 ± 4.7 mm Hg
postoperatively. Forty patients who received the GMS Plus model showed similar
IOP reduction from 25.5 ± 6 mm Hg to 18 ± 2.5 mm Hg.
Topical medication usage was also decreased in the GMS group from 1.97
± 0.74 to 1.5 ± 0.94, while the GMS Plus group began
preoperatively at 2.25 ± 0.84 and decreased medication usage to 0.85
± 0.9 at 1-year follow-up. Studies are currently under way to determine
its efficacy and safety profile as compared with traditional surgical
- Ike K. Ahmed, MD, FRCSC, can be reached at Credit Valley EyeCare,
3200 Erin Mills Parkway, Unit 1, Mississauga, Ontario L5L 1W8, Canada;
+905-820-6789; fax: +905-820-0111; e-mail:
email@example.com. Dr. Ahmed is
a consultant for Solx.
- Diamond Y. Tam, MD, can be reached at
firstname.lastname@example.org. Dr. Tam has no
direct financial interest in the products discussed in this article, nor is he
a paid consultant for any companies mentioned.