EX-PRESS implantation is â€œstraightforwardâ€

[caption id='attachment_5' align='alignright' width='300' caption='The EX-PRESS Glaucoma Filtration Device is a stainless steel, biocompatible device designed to be placed typically under a scleral flap']

[/caption] Trabeculectomy has been a stable procedure for glaucoma surgeons for years, but it is not without its issues. There are a variety of intraoperative issues that the surgeon is challenged with, including intraoperative anterior chamber shallowing, tissue trauma, and bleeding. Post-op, there are issues related to hypotony, shallowing of the anterior chamber, choroidals, hyphema, and bleb-related issues. Additionally, the surgeon needs to consider the patientâ€™s visual recovery and post-op interventions. Filtration devices have been developed to help overcome some of these challenges. In using glaucoma filtration devices, the goal is maintaining or improving efficacy and en- hancing surgical procedure safety and predictability. Implantation of the EX-PRESS Glaucoma Filtration Device (Alcon, Fort Worth, Texas) is straightforward and, with some pearls, easily mastered. In my opinion, it is an advancement over standard trabeculectomy. The step-by-step technique de- scribed has been used for more than 5 years.

Device specifics and indications

The EX-PRESS Glaucoma Filtration Device is a stainless steel, biocompatible device, about 2.5 mm in length, designed to be placed under a scleral flap. Biocompatibility is not an issue, as the device is made of the same material as cardiac implants. Itâ€™s been demon- strated as being â€œMRI safeâ€ up to 3 Tesla. Itâ€™s available in two lumen sizes, 50 microns and 200 microns. My preference is the 50-micron lumen size as it affords control. The 200-micron version has no resistance to flow but may be less likely to become blocked. Lumen blockage is rare with either lumen size and if it occurs, it can be lasered or managed with intraocular tissue plasminogen activator (TPA).

The EX-PRESS Glaucoma Filtration Device is indicated as a treatment for patients suffering from glaucoma, and for whom there is an indication, according to the physicianâ€™s judgment, for filtering surgery. For those surgeons just starting out, the ideal patient might be a pseudophakic patient with an open angle, where there is a lot of room to work with and where positioning may be less of an issue.

Surgical technique

First, administer topical lidocaine. During the surgical procedure, the surgeon should look for limbal anatomy, where the scleral fibers can be seen. Then, look for the blue zone and the clear cornea. It is important to position the flap and size it according to where the EX-PRESS device will be implanted. EnsureÂ that there is a reasonably sized flap around the implant. The thickness will ensure good control of flow post-op. Another pearl is to avoid making a thin flap, as the flap thickness will affect the deviceâ€™s success.

Under the scleral flap, a pilot hole is made with a 26-gauge (if using a hypodermic needle) or 25-gauge EdgePlus Trocar Blade (Alcon) opening into the anterior chamber. This is a critical part of the procedure to en- sure adequate positioning of the implant. Enter at the anterior spur at the level of the iris plane, facilitated with the eye pointing down. There is no need to remove a block of sclera or a large piece of tissue as in trabeculectomyâ€”that can create more trauma. Furthermore, the small pilot hole prevents the AC from shallowing during the procedure, which is a concern with trabeculectomy.Â An iridectomy is also not required with the EX-PRESS device. Rotate the implant about 90 degrees to place the implant along the long axis of the pilot hole. Rotate the EX-PRESS device to its final position when it is inside the eye. The back plate needs to be flush with the scleral bed. By planning the scleral flap around the point of insertion of the EX-PRESS device, surgeons get good lateral and posterior overlap of the flap after they complete the procedure.

Instrumentation

Some of the instruments used to implantÂ the EX-PRESS device include the A-OK Full Handle 15 Degrees (Alcon). The 15-degree blade is useful for the scleral outline, and theÂ Clear Cut HP Crescent DB (Alcon) is useful for the lamellar dissection of the flap, which is similar to a tunneling technique. The 25- gauge EdgePlus Trocar Blade makes a nice pilot hole for the EX-PRESS device P-50 model.

Intraoperative viscoelastics vs. air bubble

[caption id='attachment_6' align='alignright' width='300' caption='Ensure adequate flap overlap lateral and posterior to the EX-PRESS device to allow control of aqueous flow']

[/caption] I donâ€™t routinely use viscoelastic intraoperatively, unless there is positive pressure. If there is further concern for hypotony (which should be reduced with the device), filling the AC with viscoelastic at the end of the proce- dure may ease some of the concern. The type of viscoelastic is also important. The smaller the lumen size, the more likely the viscoelastic used will last longer or wonâ€™t be as necessary. Post-op, if you do need to refill the anterior chamber, the viscoelastic will tend to stay in the eye longer with an EX-PRESS device in place versus in a trabeculectomy. Thus, less viscoelastic may be required. Alternatively, an air bubble may be placed, which also lasts longer with the EX-PRESS device, again pointing to the added control of the device versus trabeculectomy.

Suturing

Suture tension is another important consideration because hypotony can still occur, although Iâ€™ve found fewer instances of hypotony with the EX-PRESS device than with a trabeculectomy. This could also be a factor for those who are just starting to use the device. The need to do suture lysis may be less frequent with the EX-PRESS device than with trabeculectomy (in my hands).

[caption id='attachment_7' align='alignright' width='300' caption='Suture tension is important because hypotony can still occur']

[/caption] I recommend using 10-0 nylon sutures for scleral flap sutures and 10-0 vicryl for con- junctival closure in a running horizontal mattress technique, which I think provides a nice closure. This provides a firm conjunctival closure, prevents leakage early in the procedure, and reduces the amount of tension on the bleb. Anecdotally, this may help with that morphology and can help prevent overriding bleb that can occur in the conjunctiva. For the scleral flap, two sutures should be placed in each corner, with a slipknot that can be locked. If more control is needed over flow, place additional sutures. Slipknots can help with adjusting the tension accordingly, since they can be easily tightened or loosened. To check the flow, continuously inject balanced salt solution; you can also inject some balanced salt solution into the side port to check on flow.

Wound management

Wound healing modulation is an important part of the success of the EX-PRESS device im- plantation procedure. Whatever type of wound-healing modulation that one uses or applies during trabeculectomy for controlling fibrosis should be applied for the EX-PRESS device. If a certain agent is appropriate for the particular indication and risk factors for the patient, then the same agent would be applied with the EX-PRESS device. As surgeons become more familiar with the procedure, the device, and the technique, wound manage- ment may be less of an issue. Regarding pre- and post-op medications and wound healing management, the surgeon can use the same regimen as for trabeculectomy, being careful during post-op bleb assessment.

Pearls

Blebs sometimes have to be needled. The needling technique we use for blebs is very similar with the EX-PRESS device, although itâ€™s not necessary or easy to enter the anterior chamber. Steroids and other wound-healing modalities would be applied here accordingly.

Summary

Anatomical landmarks, flap design and thick- ness remain important in this procedure. Additionally, entry points for the device are important, as well as the angle entered. In summary, there are several key steps in implanting the EX-PRESS Glaucoma Filtration Device. First, the surgeon should identify the landmarks. When we look at the sclera first, a white glistening band, this should be the highway you follow and your landmark. The blue zone is next, followed by the clear cornea. Remember those landmarks. The critical point in the technique with the EX-PRESS device is to aim at the anterior aspect of that spur. If you fail to identify this spur and rely on other landmarks, you can get into a little trouble. Finally, be sure to enter at the level of the iris plane. Itâ€™s been my experience that itâ€™s impor- tant to position the flap and size it according to where the implant will go. Approximate the scleral spur so you can plan a flap that will cover the area reasonably well. Identify the surgical limbus and use that as your entry point. I prefer about 1 mm on either side to ensure adequate flow control. Be sure to secure the flap for additional resistance. We still want to ensure that we have a reason- able size flap around the implant. By planning around the point of insertion, we can ensure we have good lateral and posterior overlap of the flap when we close the procedure.