››The traditional assumption has been that episcleral venous pressure (±8 mmHg) accounts for the lower limit of IOP achievable by eliminating the resistance of the meshwork-juxta- canalicular complex. Since IOP outcomes with Trabectome and Glaukos are usually higher, it is obvious that we do not fully understand the physiology of the outflow channels and aqueous veins.

››Surely, future studies, hopefully including randomized trials or other well-done comparative studies, will clarify the specific indications for all of these devices.

References

 1. Ophthalmic Technology Assessment (OTA) Aqueous Shunts in Glaucoma. Ophthalmic Technology Assessment, American Academy of Ophthalmology 115(2008):1089-1098.

 2. Minckler D (1999) Study design scheme, structured abstract sections and study design worksheets, [appendix to instructions for authors; page 185]. Ophthalmology 106:185–206.

 3. Minckler DS, Vedula SS, Li TJ, Mathew MC, Ayyala RS, Francis BA (2006) Aqueous shunts for glaucoma (Cochrane review). Cochrane Database Syst Rev–(2):CD004918.

 4. Wilson MR, Mendis U, Smith SD, et al. (2000) Ahmed glaucoma valve implant vs trabeculectomy in the surgical treatment of glaucoma: A randomized clinical trial. Am J Ophthalmol 130:267–273.

 5. Wilson MR, Mendis U, Paliwal A, et al. (2003) Long-term follow-up of primary glaucoma surgery with Ahmed glaucoma valve implant versus trabeculectomy. Am J Ophthalmol 136:464–470.

 6. Lima FE, Magacho L, Carvalho DM, et al. (2004) A prospective, comparative study between endoscopic cyclopho-

tocoagulation and the Ahmed drainage implant in refractory glaucoma. J Glaucoma 13:233–237.

 7. Gedde SJ, Schiffman JC, Feuer WJ, et al.; For the Tube versus Trabeculectomy Study Group (2007) Treatment outcomes in the Tube versus Trabeculectomy Study after one year of follow-up. Am J Ophthalmol 143:9–22.

 8. Heuer DK, Heuer DK, Lloyd MA, et al. (1992) Which is better? One or two? A randomized clinical trial of single-plate versus double-plate Molteno implantation for glaucomas in aphakia and pseudophakia. Ophthalmology 99:1512–1519.

 9. Hamard P, Gayroud JM, Kopel J, et al. (1997) Treatment of refractory glaucomas by transscleral cyclophotocoagulation

using semiconductor diode laser. Analysis of 50 patients followed-up over 19 months. J Fr Ophthalmol 20:125–133.

10.Fankhauser F, Kwasniewska S, Van der Zypen E (2004) Cyclodestructive procedures. I. Clinical and morphrological aspects: a review. Ophthalmologica 218:77–95.

11.Neely DE, Plager DA (2001) Endocyclophotocoagulation for management of difficult pediatric glaucomas. J AAPOS 5:221–229.

12.Gayton JL, Van der Karr M, Sanders V (1999) Combined cataract and glaucoma surgery: Trabeculectomy versus endoscopic laser cycloablation. J Cat Refract Surg 25:1214–1219.

13.Gandolfi S, Traverso CF, Bron A, et al. (2002) Short-term results of a miniature draining implant for glaucoma in combined surgery with phacoemulsification. Acta Ophthalmol Scand Suppl 236:66.

14.Minckler DS, Baerveldt G, Alfaro MR, et al. (2005) Clinical results with the Trabectome for treatment of open-angle glaucoma. Ophthalmology 112:962–967.

15.Minckler DS, Baerveldt G, Ramirez MA, et al. (2006) Clinical results with the Trabectome, a novel surgical device for treatment of adult open-angle glaucoma. Trans Am Ophthalmol Soc 104:40–50.

16.Minckler DS (1997) Glaucoma drainage devices, horsehair to silicone. American Academy of Ophthalmology Glaucoma Day Symposium, Chicago, IL, October 1996. 100 Years of Progress in Glaucoma, Chapter 19, Lippincott-Raven, Philadelphia, pp 287–292.

17.Lewis RA, von Wolff K, Tetz M, et al. (2007) Canaloplasty: circumferential viscodilation and tensioning of Schlemm’s canal using a flexible microcatheter for the treatment of open-angle glaucoma in adults: interim clinical study analysis. J Cataract Refract Surg 33(7)1217–1226.

Core Messages

››The Ex-PRESS glaucoma shunt can be used as a pressure lowering device in patients who have failed prior glaucoma surgery, or as a primary procedure.

››The Ex-PRESS has been widely adopted but has not replaced trabeculectomy.

››The procedure for implantation is similar to standard mitomycin-C trabeculectomy surgery.

››The Ex-PRESS shunt offers unique advantages and disadvantages over trabeculectomy, especially in terms of complications.

40.1  How Often Is the Ex-PRESS Mini-Shunt Being Used in Place of More Traditional Glaucoma Surgery? Have Glaucoma Specialists Adopted this Surgery?

surgery centers to treat primary, secondary, pseudophakic, and refractory glaucomas. Advocates of its use cite more reliable outcomes, which are attributed to the uniformly sized outflow path for aqueous flow. Those who have not adopted it cite the increased cost incurred by using a device during surgery that is billed as a trabeculectomy, and the small number of prospective randomized controlled trials to show its superiority over trabeculectomy [1].

Summary for the Clinician

››Many eye surgeons and glaucoma specialists have utilized the Ex-PRESS mini-shunt in their surgical practice for many different types of glaucoma.

››Those who have not adopted it cite a prior lack of prospective­ randomized control trials and its cost.

The Ex-PRESS™ (Optonol Ltd, Neve Ilan, Israel) is a miniature stainless steel glaucoma implant approved by the FDA in March 2002 that has been in use since then all over the world for the treatment of glaucoma. Currently in the U.S. alone, over 14,000 implantations have been performed in hospitals and ambulatory

M. R. Moster

Thomas Jefferson University School of Medicine, Wills Eye Institute, 840 Walnut Street, Philadelphia, PA 19107, USA

e-mail: moster@willsglaucoma.org

40.2  What Is the Ex-PRESS Mini-Shunt and How Does It Work?

The Ex-PRESS glaucoma implant is a 400 µm stainless steel (Fig. 40.1) MRI compatible and biocompatible device [2]. It was designed with the intention of offering an accurate, repeatable, and safe alternative to the primary surgical standard of care, which for decades has been the trabeculectomy. Similar to trabeculectomy, the shunt reduces intraocular pressure (IOP) by diverting aqueous humor from the anterior

Fig. 40.1  Ex-PRESS features. Despite its miniature size, the Ex-PRESS features several major structural elements. Axial orifice: a conduit for draining aqueous humor from the anterior chamber to the intrascleral space. External plate: prevents excessive

penetration. A spur: prevents extrusion of the Ex-PRESS™ from the eye. Transverse orifices: near the distal end, which constitute an alternative conduit for aqueous humor drainage in case of occlusion of the primary (axial) opening of the shunt by the iris

chamber to the subconjunctival space in order to form a filtration bleb [3]. Mitomycin C (MMC) use during the procedure is recommended to prevent scarring. The device’s unique flow-modulating design and the scleral flap under which it is implanted, control postoperative aqueous flow. Filtering surgery with the Ex-PRESS mini-shunt is a safe and standardized procedure compared to classic trabeculectomy in that it is as effective as trabeculectomy [4].

Originally the Ex-PRESS manufacturer recommended placing the device directly under the conjunctiva, but due to excessive hypotony, exposure, and other adverse effects, this technique has been abandoned [5–7]. Dahan and Carmichael first recommended implanting the Ex-PRESS shunt under a 5 × 5 mm partial thickness scleral flap, similar to a standard limbus-based guarded trabeculectomy [8]. Placing the Ex-PRESS under a half thickness scleral flap provides resistance to aqueous flow and prevents erosion. No iridectomy is required. In their initial case series of 24 eyes, MMC was placed under the scleral flap in all cases. They noted a 46%

decrease in IOP and a significant reduction in the need for medications at 1 year. However there was still a 20.8% hypotony rate with two patients (8.3%) developing choroidal effusions – one of which required drainage. In an effort to decrease the incidence of hypotony further, we recommend placing the MMC on the sclera (0.4 mg/cm3 for 1.5 min) prior to fashioning the scleral flap to avoid toxicity from MMC.

Summary for the Clinician

››The Ex-PRESS glaucoma shunt is a stainless steel device with a flow-modulating design.

››This device is MRI compatible.

››The device does not cause inflammation as the stainless steel is biocompatible.

››The Ex-PRESS shunt can be used as an alternative to trabeculectomy in patients who have had prior ocular surgery or as a primary procedure.

40.3  What Are the Ex-PRESS

Mini-Shunt’s Dimensions?

How Is It Implanted?

There are several models of the Ex-PRESS minishunt. Detailed information can be seen in Table 40.1. The Ex-PRESS shunt’s length is only 2.4–2.9 mm with an internal lumen diameter choice of either 50 or 200 µm. The Ex-PRESS glaucoma implant allows for restricted aqueous humor flow from the anterior chamber to the subconjunctival space, thereby reducing the IOP. More commonly, models with the 50 µm lumen are used for filtering surgery and are introduced through the limbus with a disposable preloaded inserter (Fig. 40.2) [9]. A 27-gauge needle for the R50

model, or a 25-gauge needle for the P50 is needed to create the anterior chamber entrance for the device. A scleral flap of one-third to one-half scleral thickness is necessary for the success of the procedure, as it will protect the device from erosion through the conjunctiva and help restrict aqueous flow in the early post-op period. Typically, MMC 0.4 mg/cm3 (although other concentrations can be used per the surgeon’s preference), is applied under the conjunc­tiva and tenons capsule for 1.5 min before the scleral flap is outlined (Fig. 40.3). Scleral flap size is usually 4 mm in both width and height (Fig. 40.4). The entry point into the anterior chamber is at the grey line where the junction of the cornea and sclera meet (Fig. 40.5). Entry into the anterior chamber is made when the chamber is inflated to an IOP of about 20 mmHg through a previously placed paracentesis. The needle entry is directed parallel to the iris and posterior to the cornea so that

Fig. 40.4  The scleral flap is usually 1/2 to 1/3 scleral thickness and 4 × 4 mm in dimension

Fig. 40.5  The shunt is inserted through a previously made opening with either a 27or 25-gauge needle (depending on model used) at the grey line. When the Ex-PRESS enters the anterior chamber there is a slight tactile “pop” when the shunt’s spur clears the cornea and is solidly within the anterior chamber. Firm pressure on the inserter causes immediate release of the device

the corneal stroma is not involved in the insertion. Perfect positioning of the device is obtained when the shunt is in the mid-anterior chamber and flush with the sclera (Fig. 40.6). In it’s final position the device should not produce corneal striae or be buried within iris stroma. When the Ex-PRESS is properly positioned immediate flow is noted through the 50 µm lumen. Aqueous flow is directed posteriorly and can be further modified by adjusting either the permanent or releasable sutures at the scleral flap (Fig. 40.7). The goal is to assure immediate aqueous flow, thereby forming a low, diffuse posterior filtering bleb with microcyst formation

Fig. 40.6  The Ex-PRESS external plate should lie flush with the sclera. There is immediate egress of aqueous noted through the 50 µm conduit

Fig. 40.7  The flow of aqueous should be directed posteriorly and can be modified with placement of sutures. Adjustable or laserable sutures work equally well

within the first 1–2 days. When using a fornix based flap (suture closure at the limbus), extreme care is advised to assure a water tight wound. If there is leakage at the limbus (positive Seidel test), it is unlikely that a posterior bleb will form and the procedure will likely fail (Fig. 40.8). A bandage contact lens or additional sutures are recommended to rectify this situation. Similar to a trabeculectomy, a combination of steroids, antibiotics, and occasionally non steroidal drugs are used post operatively. The antibiotics are stopped at 1 week, and the steroids are tapered over 4–6 weeks. This procedure can be done easily with a combination of topical and subconjunctival anesthesia known as the blitz anesthesia technique [10]. Typically, 2% lidocaine