Glaucoma Drainage Devices (Tube Shunts)
What Is a Tube Shunt and How Does It Work
Understanding the basics of this device can help you feel more prepared and confident going into your evaluation. A tube shunt works by redirecting fluid away from your eye through a carefully placed implant rather than relying on your eye's natural drainage system.
Your eye continuously produces a clear fluid called aqueous humor, which circulates inside the eye and normally drains out through a tissue network called the trabecular meshwork. In glaucoma, this drainage system becomes blocked or damaged, causing pressure to build up inside the eye. Over time, that elevated pressure presses on and damages the optic nerve, which carries visual information from your eye to your brain.
A tube shunt bypasses the eye's natural drainage channels entirely. It consists of a thin silicone tube that sits inside the front part of your eye and connects to a small plate positioned on the outer surface of the eyeball, beneath the conjunctiva (the clear tissue covering the white of the eye). Fluid flows through the tube, collects near the plate, and is gradually absorbed by surrounding tissue, keeping pressure at a safer level.
We use two main categories of drainage implants, selected based on your individual needs. Valved devices include a built-in flow restrictor that limits how much fluid can drain at one time, which helps prevent pressure from dropping too low immediately after surgery. Non-valved devices do not have this restrictor and are typically fitted with a temporary suture or stent during surgery, allowing scar tissue to form around the plate and naturally regulate flow over the first several weeks.
Common examples include the Ahmed valved device and the Baerveldt non-valved device. Dr. Anis will recommend the design that gives you the best chance of long-term pressure control based on your type of glaucoma, eye anatomy, and surgical history.
Most patients with glaucoma begin treatment with prescription eye drops, and if those are not enough, we may try laser therapy such as selective laser trabeculoplasty (SLT), minimally invasive glaucoma surgery (MIGS) procedures including micro-stent implants, or a procedure called trabeculectomy. A tube shunt is typically recommended when these earlier steps have not achieved safe pressure levels, or when your eye has features that make simpler surgeries unlikely to succeed.
- Multiple glaucoma medications cannot lower pressure to a safe level
- Laser treatments are no longer effective or are not appropriate for your type of glaucoma
- A previous trabeculectomy has failed or scarred over
- Scarring, inflammation, or other eye conditions reduce the chance of success with other surgeries
In some cases, a tube shunt may be recommended earlier in care depending on the type and severity of your glaucoma.
Who May Need a Tube Shunt
Not everyone with glaucoma will need a drainage device, but there are specific situations where a tube shunt offers the best chance of protecting your vision. Dr. Anis performs a thorough evaluation before recommending any surgical procedure.
If you have already had trabeculectomy or another drainage procedure that healed closed or can no longer control your pressure, a tube shunt may be the right next step. Eyes that have undergone prior surgery often develop excessive scar tissue, which makes repeat trabeculectomy less predictable. Tube shunts tend to resist scarring more effectively because the implant provides a durable, permanent structure for fluid to travel through.
Certain forms of glaucoma are more aggressive and may require a tube shunt earlier in the treatment process. These include conditions that cause rapid or severe pressure elevation that simpler procedures cannot reliably manage.
- Neovascular glaucoma caused by abnormal blood vessel growth from diabetic eye disease or retinal vein blockage
- Uveitic glaucoma from ongoing eye inflammation
- Angle-closure glaucoma that does not respond to laser iridotomy or lens surgery
- Glaucoma following corneal transplant or other complex eye surgeries
- Congenital glaucoma in children when other surgical options have not succeeded
Some eyes have characteristics that make trabeculectomy less likely to work well, such as thin or damaged conjunctiva, extensive scarring from trauma, or active inflammation. In these situations, a tube shunt may be recommended as the first surgical option because its design avoids many of the problems that cause trabeculectomy to fail. If you have had significant prior surgery for retinal detachment, cataracts with complications, or corneal disease, we will carefully evaluate your anatomy to determine whether a drainage device is your safest path to stable pressure control.
Before recommending a tube shunt, we perform a detailed evaluation using several diagnostic tools to fully understand your glaucoma and your eye's anatomy. This allows us to make the most informed surgical plan for your specific situation.
- Tonometry to measure your intraocular (eye) pressure
- Gonioscopy, a special lens examination to view the drainage angle inside your eye
- Automated visual field testing to map any areas of vision loss
- Color stereoscopic optic-nerve photography to document and track nerve damage
- Optical coherence tomography (OCT) to measure the thickness of optic nerve tissue in detail
Preparing for Tube Shunt Surgery
Careful preparation helps your surgery go smoothly and supports the best possible recovery. We will walk you through every step at your preoperative visit so you know exactly what to expect.
Continue using your glaucoma eye drops unless Dr. Anis specifically tells you to stop, because discontinuing them before surgery can cause a dangerous spike in pressure. If you take blood thinners such as aspirin, warfarin, or other anticoagulants, we will coordinate with your primary care physician to determine whether any adjustments are needed. Never stop blood thinners on your own, as this depends on your medical history and the specific medication involved.
Tell us about any herbal supplements you take, since some can affect bleeding or interact with anesthesia. You may be asked to avoid eating or drinking for several hours before surgery depending on the type of anesthesia planned.
Because you will receive numbing medication and possibly sedation, you will not be able to drive yourself home after surgery. Plan to have a trusted adult take you to and from the surgical center and stay with you on the first night.
- Arrange for a driver and overnight support from a family member or friend
- Wear loose, comfortable clothing that does not need to be pulled over your head
- Set up a clean, organized space at home for your postoperative eye drops
- Plan for at least one week away from work, depending on your job and how quickly you recover
Most tube shunt surgeries are performed with local anesthesia and sedation, meaning you will be relaxed and comfortable while the area around your eye is completely numbed. You may feel gentle pressure or movement but should not experience sharp pain. General anesthesia is used for children and adults who are unable to remain still or who prefer to be fully asleep during the procedure. Our anesthesia team monitors you throughout the surgery to keep you safe and comfortable.
Once your eye is fully numb, we make a small opening in the conjunctiva to access the surface of the eyeball. The drainage plate is positioned on the outer surface of the eye, usually in the upper outer area, and secured with tiny sutures. A narrow silicone tube is then threaded into the eye through a carefully created tunnel. Depending on your anatomy, the tube tip may be placed in the anterior chamber (the front space of the eye), behind the iris, or farther back in the eye if needed.
We may temporarily restrict flow through the tube with a suture or stent while your body forms a controlled layer of scar tissue around the plate. The conjunctiva is then closed with dissolvable stitches, and a protective shield is placed over your eye. The entire implant rests beneath the surface tissue and will not be visible when you look in the mirror. The procedure typically takes between 45 and 90 minutes, and most patients go home the same day.
Risks and Possible Complications
Like any surgical procedure, tube shunt surgery carries risks that we discuss openly with every patient. Most complications can be managed effectively with close monitoring and timely treatment, which is why your follow-up appointments are so important.
Some changes in the first days to weeks after surgery are fairly common and manageable, while others require prompt attention. We schedule frequent early follow-up visits specifically to catch and address these issues quickly.
- Hypotony (pressure that drops too low), which can blur vision and cause other structural changes
- Shallow anterior chamber if fluid drains too quickly or leaks from the wound
- Hyphema (bleeding into the front chamber of the eye), which usually clears on its own
- Elevated pressure during the early healing phase, particularly with non-valved devices
- Tube blockage from blood, fibrin, or debris
- Wound leak requiring additional sutures or a tissue patch
- Infection or significant inflammation needing intensive treatment
Some complications develop gradually over months or years after surgery. Regular follow-up allows us to detect these changes early and take steps to protect your vision before lasting damage occurs.
- Tube erosion through the overlying conjunctiva, which may require a patch graft procedure
- Tube blockage from scar tissue forming over time
- Tube shift or migration causing irritation or contact with other eye structures
- Corneal endothelial damage if the tube moves too close to the inner surface of the cornea
- Double vision or eye movement changes if the plate affects nearby eye muscles
- Cataract progression in patients who still have their natural lens
- Encapsulated bleb (a thick scar around the plate) that gradually limits drainage
- Serious internal eye infection (endophthalmitis), which is rare but requires urgent treatment if it occurs
Recovery and Aftercare
A smooth recovery depends on following your postoperative instructions carefully and keeping every scheduled appointment. We support you closely throughout the healing process and are always available when concerns arise.
It is completely normal for your eye to be red, swollen, and uncomfortable in the first few days after surgery. You may notice a gritty sensation, mild aching, or a feeling of fullness around your eye. Your vision will likely be blurry initially due to swelling and the ointment used during surgery, and some extra floaters or light sensitivity are common as your eye adjusts.
- Redness that slowly fades over several weeks
- Mild to moderate discomfort that typically improves with over-the-counter pain relievers
- Blurred or hazy vision for the first one to two weeks
- Light sensitivity that gradually decreases as healing progresses
After surgery, you will use antibiotic drops to prevent infection and steroid drops to reduce inflammation and control scarring around the device. We provide a detailed schedule that often starts with frequent dosing and tapers slowly over several weeks to months. Always wash your hands before instilling drops, tilt your head back, gently pull down your lower eyelid, and apply one drop at a time without letting the bottle tip touch your eye.
Taking your drops exactly as prescribed is one of the most important things you can do for a successful outcome. Skipping doses or stopping early can lead to infection or excessive scarring that blocks the tube. Because steroid drops can raise eye pressure in some patients, we monitor your pressure at every visit and adjust your regimen as needed. Bring all your bottles to each appointment so we can review your current schedule.
Certain activities need to be avoided while your eye heals to prevent injury, infection, and pressure spikes that could stress the surgical site. Your specific restrictions may vary based on your recovery, and Dr. Anis will give you personalized guidance.
- Do not rub or press on your eye, even if it itches
- Avoid swimming, hot tubs, and saunas for at least four weeks
- Avoid heavy lifting over ten pounds or strenuous exercise in the early weeks
- Wear your protective eye shield at night to prevent accidental contact while sleeping
- Avoid dusty or dirty environments that could irritate your eye
- Do not use eye makeup until specifically cleared by Dr. Anis
- Shower carefully and avoid getting water directly into the operated eye early on
We will see you one to two days after surgery for your first postoperative check, then again at one week, and at regular intervals over the following months. At each visit, we measure your eye pressure, examine the device position, and check the optic nerve. Some visits may involve minor procedures to optimize fluid flow, such as suture removal or adjustment.
Contact us immediately if you experience sudden vision loss, severe pain that does not improve, rapid worsening of redness or swelling, heavy discharge, new flashing lights, or a curtain-like shadow across your vision. These symptoms can indicate serious complications including infection, bleeding, very high or very low pressure, or retinal detachment, all of which require same-day evaluation. If you cannot reach our office promptly, seek urgent eye care right away.
Long-Term Outcomes and Monitoring
A tube shunt is a long-term solution that requires ongoing monitoring to ensure it continues working well for your eye. Most patients experience meaningful pressure reduction and vision stabilization, though outcomes vary based on the type and severity of glaucoma and individual healing patterns.
Clinical evidence shows that tube shunts can effectively lower eye pressure in many patients over several years. Success is generally measured by achieving a target pressure level, with or without additional glaucoma medications, and without requiring further surgery. It is important to understand that a tube shunt can slow or stop the progression of vision loss, but it does not restore sight that glaucoma has already taken.
Patients with neovascular or uveitic glaucoma, or those with multiple prior surgeries, may have different outcomes compared to patients with primary open-angle glaucoma. Some people eventually need additional procedures, medication changes, or a second drainage device if pressure rises again over time. Following your drop schedule, attending all appointments, and reporting any changes early are the most important things you can do to protect your vision long-term.
Even after your eye has completely healed, we continue monitoring you every three to six months for life. During these visits, we measure your intraocular pressure, examine the tube and plate, and assess your optic nerve using color stereoscopic photography and OCT imaging. We also check your visual field with automated testing to detect any subtle changes before they affect your daily vision.
These routine checks allow us to catch problems such as tube blockage, excessive scarring around the plate, or changes in drainage early enough to address them effectively. We may adjust your medications or recommend a minor procedure if your pressure trends in the wrong direction.
Many patients continue to use one or more glaucoma drops after tube shunt surgery, particularly those with advanced or aggressive disease. The device significantly reduces pressure in most cases, but may not eliminate the need for all medications. We reassess your drop regimen at every visit and aim to use the smallest number of medications needed to keep your pressure safely controlled.
Some patients are eventually able to stop all glaucoma drops if the device maintains excellent pressure control on its own. Others use fewer drops than before surgery, which can improve daily quality of life and reduce medication side effects. Our goal is always to find the simplest, most effective plan for your long-term eye health.
Frequently Asked Questions
Here are answers to questions patients often have after learning they may need a tube shunt. These responses are meant to help you think through practical decisions and know when to seek care quickly.
The drainage plate is secured to the surface of the eyeball with sutures, and the tube itself is carefully positioned during surgery, making significant movement uncommon. In rare situations, trauma to the eye or gradual changes in surrounding tissue can cause a slight shift in tube position. We check the tube placement at every follow-up visit, and if a shift causes irritation or affects how the eye drains, we can address it with a minor repositioning procedure.
The device sits beneath the conjunctiva and is typically covered by your upper eyelid, so you will not see it when looking in the mirror. Some patients notice a faint, painless firmness in the area where the plate rests, but this is rarely bothersome. You should not feel the tube inside your eye once healing is complete, and it does not interfere with blinking or normal eye movement. If you ever notice a new or unusual sensation in that area, let us know so we can examine it.
Trabeculectomy creates a small flap in the wall of the eye that allows fluid to filter out and pool in a tiny blister-like space called a bleb. A tube shunt uses a permanent silicone implant to direct fluid through a tube to a plate, where it is absorbed. The implant tends to be more resistant to scarring than the delicate opening created in trabeculectomy, which is why we often prefer it in eyes with prior surgery, inflammation, or other factors that increase the risk of trabeculectomy failure. Both procedures aim to lower pressure, but they are suited to different situations.
Most modern glaucoma drainage devices are made from non-magnetic materials such as silicone and medical-grade plastics, and the majority are considered MRI safe or MRI conditional depending on the specific model and the strength of the scanner. Always tell your MRI technologist and radiologist that you have a glaucoma implant before your scan. If possible, bring your implant identification card or a copy of your operative report so the imaging team can verify the device type and follow the appropriate safety protocols.
If your pressure rises because the tube becomes blocked or scar tissue forms around the plate, there are several options available to us. We may increase or change your glaucoma medications, use a laser or needle procedure to break up scar tissue, or perform a minor surgical revision to clear or reposition the tube. In cases where the first device can no longer provide adequate pressure control, implanting a second drainage device in a different area of the eye is sometimes the right solution. The key is catching these changes early through regular monitoring, which is why lifelong follow-up matters so much.
If a tube shunt is not appropriate for your situation, or if additional pressure lowering is needed beyond what the device can provide, there are other surgical options we can discuss. Cyclodestructive procedures, such as micropulse laser therapy, reduce the amount of fluid the eye produces by targeting the ciliary body (the tissue that makes aqueous humor). In select cases, newer minimally invasive techniques or combination surgeries may also be considered. Every decision is based on your specific eye anatomy, disease stage, and treatment history, and we will make sure you understand all the options available to you.
Trusted Glaucoma Care at Rhode Island Eye Institute
If your current glaucoma treatments are no longer keeping your eye pressure under control, we are here to help you understand your options and take the next step with confidence. Our team brings fellowship-trained expertise, advanced diagnostics, and a full range of glaucoma treatments together in one practice, so you can receive comprehensive care without being referred elsewhere. We invite you to schedule a consultation at Rhode Island Eye Institute and let us create a personalized plan to protect your vision for the years ahead.