Glaucoma Drainage Devices (Tube Shunts)
Understanding Glaucoma Drainage Devices
Your eye constantly makes a clear fluid called aqueous humor to keep it healthy and inflated. In glaucoma, this fluid cannot drain properly, so pressure builds up and damages the optic nerve over time. A tube shunt creates a new pathway for fluid to leave the eye, bypassing the blocked natural drainage channels.
The device has a thin silicone tube that sits inside the front part of your eye to collect fluid. This tube connects to a small plastic plate we position on the outside of your eyeball beneath the conjunctiva, the clear tissue that covers the white part of your eye. Fluid flows through the tube and collects under the plate, where your body absorbs it naturally, keeping pressure stable.
We use two main categories of drainage implants based on how they regulate fluid flow. Valved devices have a built-in mechanism that restricts how much fluid can drain at once, which reduces but does not eliminate the risk of pressure dropping too low immediately after surgery. Non-valved devices do not have this feature and are commonly fitted with a temporary stent or ligature that we adjust or remove later, allowing scar tissue to form around the plate and control flow over several weeks. During this early period, pressure may run higher until the device begins to drain fully.
Common examples include Ahmed valved devices, Baerveldt non-valved devices, and Molteno non-valved devices, along with smaller-plate options designed for children. Both categories have proven effective in modern practice, and we select the best option for you based on your specific type of glaucoma, your eye anatomy, and your surgical history. We will discuss which design offers you the greatest chance of long-term pressure control during your consultation.
Most people with glaucoma start treatment with prescription eye drops to lower pressure. If drops do not work well enough, we may try laser therapy, minimally invasive glaucoma surgery such as MIGS procedures when appropriate, or a procedure called trabeculectomy. A tube shunt becomes necessary when these earlier treatments fail to protect your vision or when your eye has conditions that make simpler surgeries less likely to succeed. In some cases, a tube shunt may be recommended earlier based on your disease type and eye history, rather than strictly after all other options have failed.
- Multiple glaucoma medications cannot lower your pressure to a safe level
- Laser treatments have stopped working or are not an option for your type of glaucoma
- A previous trabeculectomy failed or scarred over
- Your eye has scarring, inflammation, or other features that reduce the chance of success with other surgeries
Who Needs a Tube Shunt
If you have already had trabeculectomy or another drainage surgery that healed closed or no longer controls pressure, a tube shunt may be our next recommendation. Eyes that have undergone previous surgery often form extra scar tissue, making repeat trabeculectomy less successful. Tube shunts tend to work better in these cases because the plate and tube resist scarring more effectively than the thin openings created in trabeculectomy.
We will review your surgical history and current pressure readings to determine whether a drainage device offers you better long-term control than repeating the same procedure.
Certain forms of glaucoma are harder to control with standard treatments and may benefit from a tube shunt earlier in your care. Neovascular glaucoma, which develops from abnormal blood vessels in the eye, and uveitic glaucoma, caused by chronic inflammation, often require a drainage device because these conditions create aggressive scarring that defeats simpler surgeries.
- Neovascular glaucoma from diabetes or retinal vein blockage
- Uveitic glaucoma from ongoing inflammation
- Congenital glaucoma in children when other surgeries fail
- Angle-closure glaucoma that does not respond to laser or lens surgery
- Glaucoma after corneal transplant or other complex eye surgeries
We may recommend a tube shunt as your first glaucoma surgery if your eye has features that make trabeculectomy risky or unlikely to succeed. Eyes with extensive scarring from prior trauma, thin or abnormal conjunctiva, or active inflammation heal unpredictably after trabeculectomy. A drainage device bypasses many of these issues by using a more durable implant and placing the drainage area farther back on your eye.
If you have had extensive previous eye surgery for retinal detachment, corneal problems, or cataracts with complications, we will evaluate whether a tube shunt gives you the best chance of stable pressure and preserved vision.
Before recommending a tube shunt, we perform a comprehensive eye examination to measure your current eye pressure, assess your optic nerve damage, and test your peripheral vision with a visual field test. We use gonioscopy, a special lens exam, to look at your drainage angle and check for scarring, inflammation, or abnormal blood vessels. We also review your medical history and all glaucoma treatments you have tried.
- Tonometry to measure intraocular pressure
- Ophthalmoscopy to examine your optic nerve for glaucoma damage
- Visual field testing to map any vision loss
- Gonioscopy to inspect the drainage structures inside your eye
- Ultrasound or imaging if we need to see deeper structures
Preparing for and Undergoing Tube Shunt Surgery
We will review all your medications and supplements during your preoperative visit. You should continue using your glaucoma eye drops unless we tell you otherwise, because stopping them before surgery can cause pressure spikes. If you take blood thinners such as aspirin, warfarin, or other anticoagulants, we will coordinate with your primary doctor or prescribing clinician to decide whether you need to adjust them. Do not stop blood thinners on your own, because plans vary by your medical indication and the specific agent, and stopping without guidance can be dangerous.
Let us know about any herbal supplements you use, as some can affect bleeding or interact with anesthesia. We may ask you to avoid eating or drinking for several hours before your procedure, depending on the type of anesthesia planned.
Because you will receive numbing and possibly sedating medication, you cannot drive yourself home after surgery. Arrange for a family member or friend to take you to and from the surgical center. Plan to rest quietly for a few days afterward, and have someone available to help with daily tasks like cooking and shopping while your vision is blurry.
- A responsible adult to drive you home and stay with you the first night
- Comfortable clothing that does not pull over your head
- A clean space at home to store and use your postoperative eye drops
- Time off work or school, often at least one week depending on your job and recovery
Most tube shunt surgeries use local anesthesia with sedation, meaning you may be lightly drowsy and relaxed or more deeply sedated while we numb the area around your eye. We inject numbing medicine near your eye or use a combination of numbing drops and injections to ensure you feel no pain during the procedure. General anesthesia may be used for children or adults who cannot remain still or prefer to be fully asleep.
Our anesthesia team monitors your vital signs throughout surgery to keep you safe and comfortable. You may recall some pressure or movement sensations, but you should not experience sharp pain.
Once your eye is fully numb, we begin by making a small opening in the conjunctiva to access the white part of your eyeball. We carefully position the drainage plate on the surface of your eye, usually in the upper outer area, and secure it with tiny sutures. Next, we create a narrow tunnel into the eye and thread the silicone tube through it. Depending on your anatomy and corneal health, the tube may be placed in the anterior chamber at the front of your eye, behind the iris in the sulcus area, or farther back in the pars plana with a vitrectomy if needed. We position the tip where it can collect fluid without touching your iris or cornea.
We may temporarily cover the tube or tie a suture around it, or place a stent inside it, to control flow in the first few weeks while your body forms a controlled scar around the plate. Finally, we close the conjunctiva over the device with dissolvable stitches and apply antibiotic ointment and a protective shield. The entire implant remains hidden under the surface tissues, so only we can see it during your exams.
The procedure typically lasts between 45 minutes and 90 minutes, depending on the complexity of your case. Tube shunts are usually done one eye at a time, because same-day surgery in both eyes is uncommon and only considered in special situations. After surgery, you rest in a recovery area for about an hour while the sedation wears off and we check your pressure. Most patients go home the same day with a patch or shield over the eye and detailed instructions for aftercare.
You will receive prescriptions for antibiotic and anti-inflammatory eye drops to start the next day. We schedule your first follow-up visit within one to two days to make sure your eye is healing well and your pressure is in a safe range.
Risks and Possible Complications
As with any eye surgery, tube shunt implantation carries risks in the early healing period. Some complications are fairly common and can be managed with medication adjustments or minor procedures, while others are more serious and require urgent attention. We monitor you closely in the first weeks to detect and treat these problems early.
- Hypotony, or pressure that drops too low, which can cause blurred vision or other issues
- Shallow anterior chamber if fluid drains too quickly or leaks from the wound
- Choroidal effusion or choroidal hemorrhage, fluid or bleeding in the layers behind the retina
- Hyphema, bleeding into the front chamber of the eye that usually clears on its own
- Early high pressure and hypertensive phase, especially with non-valved devices before full drainage begins
- Tube blockage from blood, fibrin, or other debris
- Wound leak requiring additional sutures or tissue patch
- Infection or severe inflammation needing intensive treatment
- Need for additional procedures such as stent or ligature adjustment or anterior chamber reformation
While most patients do well long-term, complications can occur months or years after surgery. Regular follow-up allows us to detect these changes and intervene before vision is affected. Some late problems require medication adjustments, laser or needle procedures, or surgical revision.
- Tube erosion through the overlying conjunctiva requiring a patch graft
- Tube blockage from scar tissue or inflammatory debris
- Tube malposition or migration, sometimes causing irritation or damage to other structures
- Corneal endothelial damage if the tube touches the inner cornea, or chronic endothelial cell loss leading to corneal decompensation over time
- Diplopia or double vision and motility disturbance if the plate affects nearby eye muscles
- Cataract progression in patients who still have their natural lens
- Encapsulated bleb, thick scar around the plate that limits drainage
- Persistent low pressure causing vision problems or structural changes
- Chronic inflammation or infection around the device, though rare with proper care
- Risk of endophthalmitis, a severe infection inside the eye, especially if the tube erodes
Recovery and Aftercare Following Surgery
It is normal for your eye to be red, swollen, and uncomfortable for the first few days after surgery. You may notice a gritty or scratchy sensation, mild aching, or a feeling of fullness around your eye. Your vision will be blurry at first, both from swelling and from the ointment we use. You might see extra floaters or shadows as your eye adjusts to the device.
- Redness that gradually fades over several weeks
- Mild to moderate discomfort that improves with over-the-counter pain relievers
- Blurred or hazy vision for the first week or two
- Light sensitivity that decreases as healing progresses
You will use antibiotic drops to prevent infection and steroid drops to reduce inflammation and control scarring. We will give you a detailed schedule, often starting with drops every few hours and then gradually tapering over several weeks or months. Always wash your hands before using drops, tilt your head back, pull down your lower lid, and apply one drop without letting the bottle touch your eye.
Using your drops exactly as prescribed is critical to successful healing. Missing doses or stopping too soon can lead to infection or excessive scarring that blocks the device. Steroid drops can raise eye pressure in some patients, so we monitor your pressure closely at every visit and adjust your medications as needed. Keep all your drop bottles clean, store them as directed, and bring them to every follow-up appointment so we can review your regimen.
Activity restrictions vary by surgeon and your individual healing, but most patients are asked to avoid actions that could jar the eye, raise pressure suddenly, or introduce bacteria for the first few weeks. Do not rub or press on your eye, even if it itches. Skip swimming, hot tubs, and saunas until we clear you, as these can cause infection. Avoid heavy lifting, straining, or bending over, because these actions increase eye pressure and stress the healing tissues.
- No eye rubbing or touching the surgical area
- No swimming, diving, or water sports for at least four weeks
- No heavy lifting over ten pounds or strenuous exercise in the early weeks
- Wear your protective eye shield at night to prevent accidental injury
- Avoid dusty or dirty environments that could irritate your eye
- Avoid eye makeup until your surgeon clears you
- Shower carefully and avoid getting water directly in your eye early on
- Ask your surgeon when it is safe to drive, because this depends on your vision recovery
- Avoid sleeping on the operated side initially if advised
We will see you one or two days after surgery for your first postoperative check. During this visit, we measure your eye pressure, examine the device position, and make sure there are no early complications. You will return again at one week, then at regular intervals over the first few months. We may adjust your drop schedule, remove sutures, or perform minor procedures to optimize fluid flow through the tube.
Keeping every appointment is essential because we monitor your pressure closely and catch problems early. Even after your eye has healed, you will need lifelong follow-up visits every few months to ensure the device continues working properly.
Call our office immediately if you notice sudden vision loss, severe pain that does not improve with over-the-counter medicine, or a large increase in redness or swelling. These symptoms can signal serious complications like infection, bleeding inside the eye, or very low or very high pressure. A sudden shower of new floaters, flashing lights, or a curtain across your vision can indicate retinal detachment and requires urgent evaluation. If you cannot reach us promptly, seek urgent or emergency eye care the same day.
- Sudden decrease in vision or complete vision loss
- Severe or worsening eye pain
- Heavy discharge, especially yellow or green
- Rapidly increasing redness or swelling
- Nausea, vomiting, or headache with eye pain
- New or worsening light sensitivity with decreasing vision
Long-Term Outcomes and Monitoring
Clinical studies show that tube shunts can successfully lower eye pressure in many patients over several years. Success is usually defined as achieving a target pressure reduction with or without additional glaucoma medications, and sometimes without needing further surgery. However, outcomes vary widely depending on your type of glaucoma, how advanced the disease is, whether you have had previous surgery, and which device is used.
Patients with neovascular glaucoma, uveitic glaucoma, or multiple prior surgeries may have different success rates than those with primary open-angle glaucoma and no previous operations. Some patients eventually need additional procedures, adjustments, or even a second drainage device if pressure rises again. Most people experience significant pressure reduction and stabilization of their vision with a tube shunt, though the device does not restore vision already lost to glaucoma. Long-term outcomes are generally better in patients who follow their drop schedules, attend all appointments, and report problems early.
Even after your eye has fully healed, we will monitor you every three to six months for life. During these visits, we measure your intraocular pressure, examine the appearance of the tube and plate, and check your optic nerve and visual field. We look for signs that the device is draining too much or too little fluid, or that scar tissue is forming in a way that could block flow.
We may perform imaging tests or use special lenses to see the tube tip inside your eye. These routine checks allow us to detect changes early and adjust your medications or recommend additional procedures if needed to maintain stable pressure.
Many patients still require one or more glaucoma eye drops after tube shunt surgery to reach their target pressure. The device significantly reduces pressure in most cases, but it may not eliminate the need for all medications, especially in advanced or aggressive glaucoma. We tailor your drop regimen to your individual pressure goals and reassess it at every visit.
Some people eventually stop all glaucoma drops if their device maintains excellent pressure control on its own. Others use fewer medications than before surgery, which can improve their quality of life and reduce side effects. We will work with you to find the simplest regimen that keeps your pressure safe and your vision stable.
Frequently Asked Questions
The drainage plate is securely sutured to the surface of your eyeball, and the tube is carefully positioned and often anchored as well, so movement is uncommon. In rare cases, trauma to the eye or gradual tissue changes can cause the tube to shift slightly, and we monitor for this at every visit. If the tube does move enough to cause problems, we can reposition it with a minor surgical procedure.
You should not see the device when you look in the mirror because it sits beneath the conjunctiva and is usually covered by your upper eyelid. Some patients notice a slight, painless elevation or firmness in the area where the plate rests, but this rarely causes discomfort. You will not feel the tube inside your eye, and it should not interfere with blinking or moving your eye once healing is complete.
Both procedures create a new drainage pathway to lower eye pressure, but they work in different ways. Trabeculectomy makes a small flap in the eye wall to let fluid filter out and form a bleb, a blister-like area under the conjunctiva. A tube shunt uses a permanent silicone implant to direct fluid to a plate, which tends to resist scarring better than the delicate trabeculectomy opening. We may choose a tube shunt if you have factors that make trabeculectomy less likely to succeed, such as previous surgery or inflammatory conditions.
Most current glaucoma drainage devices are made from non-magnetic materials like silicone, polypropylene, or other plastics that are generally safe in MRI machines, though some are MRI safe and others are MRI conditional depending on the model and scanner strength. Always inform your MRI technologist and radiologist that you have a glaucoma implant, and bring your implant card or operative note details if available so they can confirm the device type and follow site protocols.
If your pressure rises because the tube becomes blocked or too much scar tissue forms around the plate, we have several options. We may adjust your glaucoma medications, use a laser or needle to open scar tissue, or perform a minor surgical revision to clear the tube or reposition it. In some cases, we may need to implant a second drainage device in a different area of your eye if the first one can no longer provide adequate control.
If a tube shunt is not suitable for you or if your glaucoma requires additional pressure lowering, we may consider cyclodestructive procedures such as micropulse laser treatment to reduce fluid production by the ciliary body. In select cases, repeat trabeculectomy, newer minimally invasive techniques, or combination surgeries may be options. We will discuss all alternatives that may help preserve your vision based on your individual eye condition and treatment goals.
Getting Help for Glaucoma Drainage Devices
If you have been told you need a tube shunt or your current glaucoma treatments are not controlling your pressure, your ophthalmologist is ready to discuss your options and answer your questions. We will perform a thorough evaluation, explain the surgery in detail, and create a personalized treatment plan to preserve your vision for the long term.