The XEN® Gel Stent comes in two different lumen (internal diameter of the stent) sizes, XEN®45 (45 micron lumen size) and XEN®63 (63 micron lumen size). The larger the lumen, the more fluid can pass through. Your surgeon will review the pros and cons of using one size over the other and which option would be safest and most effective for you.

The XEN® Gel Stent is made out of porcine collagen, therefore it is not radio-opaque and does not have any metal in it. It will not be seen on an X-ray or CT scan. Theoretically, if the MRI images are very focused, it may be visible on an MRI. It can be seen on an ocular ultrasound or OCT of the anterior chamber of the eye.

It is safe to have an MRI with a XEN® implant since it is not made out of metal.

A XEN® Gel Stent can be implanted into the eye from the inside of the eye (ab interno), or from the outside (ab externo). Generally, implantation from the inside is faster, but can also be technically challenging and therefore, most surgeons prefer to implant from the outside of the eye. This allows for dissection of the surface tissues of the eye to avoid plugging of the stent as in is implanted. Mitomycin C is an anti-metabolite drug used during this surgery to reduce scarring and surgical failure (see below for details). After surgery, 5-fluorouracil, another anti-metabolite, may also be used an an eye injection to reduce scarring. These treatments may be performed at follow-up clinic visits.

In general, XEN® implant surgery has similar potential complications when compared to traditional trabeculectomy surgery for glaucoma. However, the complications are less frequent, recovery is faster, vision is less blurry for less time, and there are overall less frequent post-operative visits.

Vision is blurry after the surgery but there is a faster recovery compared with trabeculectomy surgery. Rarely, especially if you already have very severe glaucoma damage to the optic nerve, you can suffer further permanent vision loss after surgery. This is rare, but can happen, even with routine, uncomplicated surgery. Other possible complications can include very high or very low pressures after surgery, over drainage of fluid causing collapse of the front chamber of the eye (rare with XEN®45; can occur with XEN®63 but can be prevented with the use of a partial suture plug), wound leak, accelerated development of cataract, bleeding during or after surgery (which can be minor or major causing usually temporary but sometimes permanent vision loss), infection (rare but when severe can cause loss of the eye) or retinal detachment (rare with XEN® surgery alone, but higher when cataract surgery or vitrectomy is done at the same time). Rarely, the XEN® implant can become exposed and require removal to prevent infection. (Please note: This is not an exhaustive list, but covers the most note-worthy potential risks.)

Please note that although this is a scary list of possible complications, most of these issues are treatable with reasonable ultimate outcomes. If you encounter a complication, every effort will be made to remedy the situation as much as possible, including further medication, laser or further surgery as needed. Your surgeon will discuss these options with you. Your patience and cooperation is greatly appreciated during this time since this will help the healing process immensely.

Mitomycin C (MMC), a drug used in chemotherapy, has been a useful tool in glaucoma surgery to prevent scarring of the tissues around the stent, causing it to be plugged. MMC is used either as a minute injection prior to dissection of the conjunctiva (outer tissue later of the eye), or applied with MMC soaked sponges under the conjunctival and Tenons (fascial layer) after it is opened up. If sponges are placed, they are removed after a certain number of minutes, and the area is thoroughly rinsed. Care is taken to avoid exposing the edges of the wound and the inside of the eye to MMC. Without the use of MMC, the XEN® implant would eventually become blocked due to scarring, filtration would stop and the surgery would be unsuccessful.

These medications are anti-metabolites that prevent new cell growth. They are used to stop fibroblasts or scar-making cells from growing. They can sometimes affect the growth of normal cells, and cause delayed healing, persistent wound leak or thinning of the surrounding tissues, or corneal roughness and irritation. These drugs are used on the surface of the eye and are applied cautiously to prevent problems with the wound. However, if they get inside the eye, which is extremely rare due to the way they are used, they can potentially cause damage to the cornea, lens and other structures in the eye. A non-healing wound leak will be repaired by your surgeon since it can lead to infection, bleeding or very low pressures that all can cause poor vision or vision loss. Symptoms of such problems would be eye pain, excessive tearing, redness, or vision loss. If you experience these symptoms, you should contact your surgeon's office, or after hours, go to Misericordia Health Centre or your local emergency department as soon as possible.

The reason you are being offered surgery, is because you are already at risk of losing more vision if your eye pressure remains uncontrolled. You are being offered surgery at this point because the benefits of doing surgery now, outweigh the possible risks.

Successful XEN® surgery will ensure a low pressure for several years, sometimes requiring extra glaucoma drops to help keep the pressure down. Unfortunately, this effect may last 5 to 10 years (or more or less) and then another procedure or a revision of the surgery will have to be done to maintain an acceptable eye pressure. It is important to understand, that glaucoma is a progressive disease that changes over time. Regular monitoring and check-ups will ensure that you are keeping up with the changes. Although we cannot cure glaucoma, we can treat it effectively to help prevent significant vision loss during your lifetime.

In order to work, the XEN® tube has to remain unplugged. Unfortunately, especially in the early part of the recovery period, our body's natural tendency to close wounds will sometimes cause too much scarring around the implant. This can lead to blockage of the implant. During the surgery, your surgeon will use Mitomycin C, an anti-scarring medication used in chemotherapy, in very minute doses to prevent scarring. However, despite this, excessive scarring can still occur. Therefore, in the weeks right after surgery, careful monitoring and extra treatment is done to make sure the XEN® heals without too much scarring. You should expect several visits with your surgeon during this time.

These steps may include: putting you temporarily (or in some cases permanently) back on glaucoma drops, or doing a series of 5-FU (Fluorouracil) injections to the superficial surface of the eye. 5-Fluorouracil is another anti-scarring, chemotherapy medication used in minute doses to work against aggressive scarring in the early days or weeks after the surgery. At GEM Clinic, it is done in the office, on a weekly or biweekly basis for up to 5 injections (or as needed). Occasionally, you may need a revision if the XEN® stops working due to being plugged by a thick scar.

After all these efforts, if you still do not have good pressure control, you may need to have another type of surgery called Glaucoma Drainage Implant (Device) surgery with either an Ahmed or Baerveldt Glaucoma Drainage Device.

If you are having glaucoma surgery for the first time, XEN® implant surgery is a good initial step that does not involve as much disssection as with a traditional trabeculectomy. When a XEN® implant works well, it can lower the pressure to almost as low as the trabeculectomy with less potential complications. It is usually a shorter operation than both the trabeculectomy and the Ahmed and Baerveldt surgeries, with less frequent follow-ups. However, if you need to have a second glaucoma surgery, an implanted device may be the appropriate next step.

Routine XEN® surgery will take about 20-30 minutes (longer if any problems arise). When combined with cataract surgery, it can take up to an hour. You will need to be at the hospital 1.5 hours before your surgical time so that the hospital staff can get you ready for the surgery. After your surgery, you will have about 30 minutes to recover, and then will be able to go home. Usually, the entire visit for day surgery at the hospital will take about 4 hours.

You will be well frozen with local anaesthetic around the eye, therefore you should not feel anything during surgery. If you do have any discomfort or pain, you will be able to tell your surgeon this, and more anaesthetic will promptly be applied.

It is normal to feel some discomfort and irritation from the superficial stitches, and some light sensitivity after surgery. The vision is usually blurry initially.

Symptoms such as severe pain, headache, vision loss, nausea and vomiting are unusual. If you experience any of these symptoms, you should contact your surgeon's office, or go back to Misericordia Health Centre immediately.

XEN® implant surgery is much different than routine cataract surgery. Blurred vision after XEN® implant surgery (alone or combined with cataract surgery) can last for several weeks after the surgery with steady improvement. When you have cataract surgery combined with any type of glaucoma surgery, you will need to get your glasses updated about 2 months after the surgery when things are stable. In comparison, when you have cataract surgery alone, you can update your glasses at least 1 month after surgery.

Rarely, especially for people who already have severe damage to their optic nerves from glaucoma, surgery can worsen vision permanently. This is rare, but can happen even with uncomplicated surgery. This may happen because the optic nerve in a person with advanced glaucoma may be too weak to tolerate the surgical trauma. Sometimes, a decision is made to avoid surgery, since the risk of losing vision is too high. However, in most cases, if there is persistently high eye pressure, surgery must proceed regardless of the risks, in order to prevent further damage to an already weakened nerve. Your surgeon will discuss the risks and benefits of surgery with you ahead of time, so that you can make an informed decision for your future eye health.