About Dr Brian Ang

Glaucoma Treatment With The XEN Gel Stent

Why is implantation of the XEN Gel Stent necessary?

A XEN Gel Stent is implanted in patients with worsening glaucoma or uncontrolled high eye pressure despite being on medications.

(Image adapted from the internet)

Fluid in the eye (aqueous) is produced by the ciliary body, and drains out through the trabecular meshwork (drainage pathway) in the drainage angle. Sometimes the trabecular meshwork becomes unable to cope, preventing aqueous from draining out easily. This causes pressure to build up in the eyeball. When the pressure in the eye is too high, it can cause optic nerve damage and permanent vision loss – this is called glaucoma.

The XEN Gel Stent reduces eye pressure, which in turn reduces the risk of further optic nerve damage from glaucoma.

See Related: Surgical treatments for glaucoma

What does the XEN Gel Stent do?

The XEN Gel Stent is made of porcine gelatin material, and measures 6 mm long. It is inert and will remain permanently in the eye.

In contrast to traditional glaucoma surgery, implantation of the XEN gel stent is quicker, easier to perform, with less risk of complications. The pressure control achieved is similar to that of standard trabeculectomy.

Implantation of the XEN Gel Stent involves:

● Making self-sealing incisions in the clear front window of the eye (cornea).
● Applying an anti-scarring medication (mitomycin-C) to prevent scarring
● Implanting the XEN Gel Stent through the drainage angle, so that the
   external part of the stent sits in the space under the skin of the eye
   (subconjunctival space) while the internal part of the stent remains within
   the eyeball.
● This allows aqueous to drain out of the eye into the subconjunctival space in
   a controlled manner to form an elevation called a bleb. The aqueous in the
   bleb is eventually absorbed by the surrounding blood vessels.

The procedure takes approximately 20 minutes, with no stitches required.

(Images adapted from the internet)

See Related:

Trabeculectory surgery for glaucoma

Drainage tube shunt surgery for glaucoma

What are the potential risks?

(Image adapted from the internet)

XEN Gel Stent implantation has a success rate of around 70-80%. Most complications can be treated, although sight-threatening complications may occur rarely (less than 1 in every 100). These can sometimes occur even if the operation has been carried out perfectly.

If you have severe glaucoma, there is a risk of completely losing all vision due to the stress of the procedure (this is called snuff-out).

Risks during surgery:

 Bleeding into the eye. If bleeding is severe, the operation may be
    discontinued, and will need to be completed on another day.
● Failure of the XEN Gel Stent to be implanted in the correct position.
● Damage to other parts of the eye. This will prolong the surgery and your
   eye may take a few months to recover instead of a few weeks.

Risks after surgery, where treatment does not involve another procedure:

● Bruising of the eye or eyelids. This is quite common.
● Allergy to the post-surgery eye drops, causing redness and irritation of
   the eye and eyelid.
● Low pressure in the eye (hypotony). This usually settles over the course
   of several weeks to months. Occasionally, it can be severe and cause
   reduced vision in the long term.

Risks after surgery, where treatment requires another surgical procedure:

● Failure. Scarring around the XEN Gel Stent prevents aqueous from draining
   out of the eye. During your postoperative visits, you may receive multiple
   injections of anti-scarring medication (5-fluorouracil) around the stent to try
   to prevent the scar tissue from forming. Sometimes, the scar tissue needs
   to be cut with a blade or needle to free up the stent (needling procedure).
● High pressure in the eye. The pressure can be reduced by needling the
   scar tissue obstructing the XEN Gel Stent. If the pressure remains
   persistently high, you may require pressure-lowering drops or tablets.
● Infection inside the eye (endophthalmitis). This is the most serious
   complication and may cause permanent sight loss despite treatment with
   antibiotics and surgery.
● Cloudiness of the lens in the eye (cataract). This can be treated with
   cataract surgery.
● Droopiness of the eyelid (ptosis). This is usually mild. However if this
   causes problems, the eyelid can be lifted by tightening the eyelid muscle
   (ptosis surgery).

See Related: Risks and complications of glaucoma surgery

What should I expect?

Implantation of the XEN Gel Stent is a hospital-based day case procedure performed under local anesthetic. The operation is usually performed one eye at a time.

Before surgery:

On the day of your procedure, please take all your usual medications unless otherwise advised. You will need to fast for at least 6 hours before your procedure. You will not be able to drive home on the day of the procedure, so you will need to arrange for someone to take you home. Please allow at least 3 to 4 hours in the hospital.

Before the XEN Gel Stent implantation, you will receive the following:
● Eye drops to constrict the pupil. These can take up to 30 minutes to work.
● Cannula inserted into a vein, usually at the back of your hand.
● Local anesthetic eye drops prior to the anesthetic injection.
● Local anesthetic injection into the eye socket to fully numb the eye.

During surgery:

To reduce the risk of infection, povidone iodine antiseptic is used to clean your eye and eyelashes, a sterile drape will cover your face, and a sterile clip will keep your eyelids open.

You will be awake during surgery, but you should not feel any pain. If you feel discomfort or pain, additional local anesthetic can be given. It is normal to notice bright lights or colors, hear buzzing and beeping sounds, and feel cold water running down your cheek or ear.

You will need to lie relatively still for up to 30 minutes for the operation. At the end of surgery, you may feel a sting due to an injection.

After surgery:

After the operation, a pad and shield will be placed over your eye. The pad and shield can be removed the next day, and you can start your postoperative eye drops. These comprise:

● Steroid anti-inflammatory eye drops (Prednisolone or Dexamethasone)
   2-hourly for 4 to 6 weeks. These drops will be decreased gradually over
   several months.
● Antibiotic eye drops (Chloramphenicol) 4 times daily for 1 week.

You will need to stop your glaucoma eye drops (if any) to the operated eye. However, please continue your usual eye drops to the non-operated eye.

Over the next few weeks, you will experience blurriness, discomfort, sensitivity to light, and blood around the eye. These will gradually improve over several weeks with the eye drops. Please avoid strenuous activity during this period.

You will be reviewed the next day, and then weekly for a few weeks after surgery. During these visits, you may receive injection of an anti-scarring medication (5-fluorouracil) around the bleb. The visits (and injections) will become less frequent as the eye settles.

Please contact the clinic immediately if you experience pain or a sharp drop in vision.

See Related: 

Patient guide to bleb revision surgery

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