If you have had a trabeculectomy that is no longer working to control the eye pressure, or if you have a difficult type of glaucoma such as Neovascular Glaucoma (eg from Proliferative Diabetic Retinopathy) or Uveitic Glaucoma, for which trabeculectomies do not work well in the first instance, then an Ahmed implant will help to control the pressure quicker and longer than a trabeculectomy.

A Baerveldt® Implant is a larger drainage device than an Ahmed® implant. In studies comparing an Ahmed® and Baerveldt® implant, the Baerveldt® implant seems to provide a longer lasting pressure lowering effect. However, the downside is that it can sometimes cause the eye pressure to become too low, which is also not healthy for the eye. Also, a Baerveldt® implant does not have a built-in valve system like the Ahmed® Implant, therefore it must be tied off with a dissolvable stitch so that it will not start working until the eye wound heals and the tie dissolves about 4-6 weeks after the surgery. If you need immediate eye pressure lowering, an Ahmed® Implant may be a better choice. However, if your eye pressures can be controlled with eye drops and medications for a few more weeks (depending on your response to medications and your eye nerve health), a Baerveldt® usually provides better pressure lowering for a longer period of time with fewer additional medications and fewer surgical revisions. It is very effective in patients who have high eye pressures despite being on maximum medical therapy with drops and pills.

A ClearPath® is very similar to a Baerveldt® in that it does not have a valve and is has similar sizes. It has a slightly different shape than the Baerveldt® making it somewhat easier to insert with less irritation to the muscles around the eye.

In Ahmed®, Baerveldt® and ClearPath® Implant surgery, an alternate drainage pathway is made to bypass your poorly functioning drainage system. It is like getting "new plumbing" for the eye. All these devices are made of a silicone tube and plate. The tube of the implant (whichever is being used) is inserted into the front of the eye to allow fluid to drain out of the eye and onto the plate. The plate sits on the outside of your eyeball and is stitched securely, just under the surface skin of the eye, called the "conjunctiva". Watery fluid from inside the eye drains through the tube and collects over the plate and just under the conjunctiva. This fluid collection may be visible as a slight bump over the plate, which is hidden by your eyelid. Eventually the fluid is absorbed. You will not notice the fluid draining unless there is a leak, which usually goes away by itself, or may need to be stitched closed. This extra drain in the eye makes the eye pressure lower. However, often it is still necessary to use glaucoma eye drops to get the pressure into an acceptable range.

Ahmed®, Baerveldt® and ClearPath® Implants are all Glaucoma Drainage Devices used to improve the "plumbing" of your eyes and lower eye pressure if medications, laser and trabeculectomy surgery have failed. An Ahmed® Implant has a built in valve that enables it to lower eye pressure immediately after the surgery. This is a fast and effective fix for patients who have high pressures despite taking many eye medications to lower their eye pressures. A few weeks after Ahmed® Implant surgery, when the wound heals over, the pressure may increase and eye drops may have to be restarted to lower the eye pressure. Usually, with some glaucoma eye drops and the Ahmed® implant in place, the eye pressure comes into an acceptable range.

A Baerveldt® and ClearPath® Implants do not have a built in valve like the Ahmed®. They need to be tied off with a dissolvable stitch so that the wound has a chance to heal over, before it starts draining fluid from the eye (once the dissolvable tie disappears). If this is not done, the fluid from the eye will drain too quickly, and flatten the front of the eye, causing a lot of problems. Because they needs to be tied off, these implants do not start working right away. Therefore, they are more appropriate for patients who can wait another 4-6 weeks before pressure is lowered (depending on eye health and medication response). You would need to continue using your glaucoma eye drops and possibly the oral medications as well for the initial 4-6 weeks (sometimes longer). Once the Baerveldt® or ClearPath® implant starts working after the stitch around the tube dissolves, they usually provide better pressure lowering over a longer period than an Ahmed® Implant. At this point, most of the glaucoma medications can be stopped.

These surgeries are done with a local anaesthetic and intravenous (IV) sedation. You will be awake but sleepy during the surgery. This is much safer than using a general anaesthetic. You will not be able to feel anything. If you have any discomfort, more freezing can be used.

The Ahmed® and ClearPath® will not show up on an X-ray, but will be visible on CT scan and MRI images. The Baerveldt® is "radiopaque" and will show up on all three imaging studies. None of these implants have any metal in them, therefore they are safe for use with MRI scanning.

The tube is covered with a piece of graft tissue, which is a piece of donated eye tissue used for transplantation purposes. It may be clear corneal tissue or a white piece of scleral tissue. This is to provide further protection against exposure and to make the wound stronger. This tissue is soaked in strong antibiotics before being used. After a few years, it may need to be replaced if it becomes too thin and the tube starts becoming exposed. This would require a revision of the initial surgery, which would be determined at a follow-up visit. Exposure of the tube may cause irritation, redness or soreness and could be a risk factor for infection, therefore any symptoms like these should be checked by your surgeon or eye health care professional as soon as possible.

Many "sutures" or stitches are used in this surgery. The stitches holding the implant in place are permanent. All the other stitches are dissolvable. You may feel the superficial stitches just after the surgery for a few days. After that, they usually soften up and are less irritating. They usually will disappear after a few weeks, but occasionally your surgeon will remove them during a clinic visit.

Ahmed®, Baerveldt® and ClearPath® Implant surgery is much different than routine cataract surgery. Often the vision is blurry for weeks after the surgery, but it gradually gets better. Occasionally, especially if you already have very severe glaucoma damage to the optic nerves, you can suffer further permanent vision loss after surgery. This is rare, but can happen, even with 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, 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 implant surgery alone, but higher when cataract surgery or vitrectomy surgery is done at the same time). Double vision right after the surgery is common, but also can sometimes persist after the wounds have healed. Late complications can include exposure of the tube and possible infection as the covering over the tube breaks down over time. (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.

Anaesthetic complications are extremely rare but can happen even with the small amount of intravenous medications and local anaesthetics that are used. Most of the time, if a patient is comfortable, no drugs are used. However, if a patient is nervous and needs something to stay relaxed, a small amount of sedatives and painkillers are used in the intravenous. In some patients, use of local anaesthetics in and around the eye can cause decreased vision, bleeding and nerve changes. These effects are usually temporary and resolve with time. Rarely, there can be permanent damage. In rare patients with multiple medical problems, these drugs can potentially cause cardiac or neurological problems, resulting in serious illness or even death. We are certainly vigilant of any concerns with the use of medications in our patients and are prepared to deal with these kinds of emergencies. However, we cannot always predict when a serious drug reaction will occur. Thankfully, these complications are extremely rare with local procedures.

These are all serious potential risks, however, the reason you are being offered surgery, is because you are already at risk for 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 potential risks.

Ahmed®, Baerveldt® or ClearPath® Implant surgery will ensure a low pressure for several years, usually 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.

Blurred vision often lasts for several weeks after the surgery, even if you have cataract surgery at the same time. It will gradually get better. Ahmed®, Baerveldt® or ClearPath® Implant surgery is much different than routine cataract surgery. If you have cataract surgery at the same time as 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 change your glasses about 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.

Ahmed® Implant surgery may take 45 minutes to an hour. When combined with cataract surgery, it can take just over 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 30-40 minutes to recover, and then will be able to go home. You will be given an appointment to see your surgeon the next day and a detailed instruction sheet before leaving the hospital. Your prescription will be faxed to your pharmacy before your surgery. Your eye will be patched after the surgery. You can take the patch off at home after 5 hours and start using the new eye drops. Usually, the entire visit for day surgery at the hospital will take about 4 hours.

Baerveldt® or ClearPath® Implant surgery may take 45 mins to an hour. When either is combined with cataract surgery, the surgery can take just over an hour to an hour and a half. 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 30-40 minutes to recover, and then will be able to go home. You will be given an appointment to see your surgeon the next day and a detailed instruction sheet before leaving the hospital. Your prescription will be faxed to your pharmacy before your surgery. Your eye will be patched after the surgery. You can take the patch off at home after 5 hours and start using the new eye drops. Usually, the entire visit for day surgery at the hospital will take about 4 hours.

There are a few drops you will need to take after surgery to prevent infection and control inflammation. Your glaucoma drops are stopped after Ahmed implant surgery. The Ahmed Implant usually starts working right away to lower the eye pressure. Sometimes the pressure is very low right after the surgery. However, often, healing and scarring cause the pressure to gradually creep up again about 3-4 weeks after the surgery. At this time, it is necessary to restart some or all of the glaucoma drops. The implant along with the eye drops will lower the pressure to an acceptable range. Occasionally, no further glaucoma drops are required after surgery. If you were taking oral medications before the surgery, these can be stopped after surgery and usually do not need to be restarted.

After Baerveldt® or ClearPath® implant surgery, you will still need to continue your glaucoma drops for at least 6-8 weeks after the surgery until the implant starts working. If you are taking oral medications to lower your eye pressure, you will be advised if you need to continue taking them or not, based on your eye pressure the day after surgery. There are also a few drops you will need to take after surgery to prevent infection and control inflammation. Once the dissolvable stitch around the tube has disappeared and the tube starts draining fluid from your eye, the eye pressure will decrease. This usually happens after 6-8 weeks. You will be instructed to stop all or some of your glaucoma eye drops and medications at that time.

The implant is permanently implanted in your eye. Rarely, if it was causing infection, shifting position or becoming exposed, it would be removed.

Usually you do not feel anything. It becomes part of your eye and does not feel any different. Occasionally, a cyst develops over the implant that my cause it to feel bumpy. In this case, the surgery may have to be revised.

Yes, sometimes, there is a cyst or scar tissue that develops over the plate of the implant which "blocks" the filter. In this case, the eye pressure can increase again. Cutting out the cyst or scar tissue can help lower the pressure again and allow the implant to drain fluid again properly. This surgery is done under local anaesthetic and takes about 15-30 minutes.

Sometimes, the graft tissue covering the tube can degrade and become visible and exposed. In this case, a revision must be done to cover the tube properly again with new graft tissue. This revision is done under local anaesthetic and takes about 45 minutes to an hour, since the dissection is often very tedious. For this reason, sometimes your surgeon may consider doing a revision with new tissue when the covering is looking very thin before the tube gets exposed. This takes less time, the recovery is faster and any risk of infection from an exposed tube is prevented.

These procedures are reasonably comfortable and well tolerated.

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.

After surgery, it is normal to feel some discomfort and irritation from the superficial stitches, and some light sensitivity after Ahmed or Baerveldt Implant surgery. It is unusual to "feel" the implant since it is buried under your surface skin. The vision is usually blurry right after surgery for several weeks.

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.