There are 2 main categories: Valved Devices and Non-Valved Devices.
Valved devices are designed to allow controlled aqueous humor outflow once intraocular pressure (IOP) exceeds a specific threshold, helping prevent early postoperative hypotony (excessively low IOP). They are particularly useful in high-risk glaucomas or eyes prone to developing low pressures.
Non-valved devices lack a built-in flow control mechanism. Instead, they rely on the resistance offered by the fibrous capsule that forms around the implant several weeks after surgery. Because they allow unrestricted flow, surgeons must temporarily block or restrict flow early post-op to prevent hypotony (dangerously low IOP). Once a fibrous capsule forms (usually 4–6 weeks), controlled flow begins.
Valved devices begin regulating IOP immediately after surgery, making them ideal for cases where rapid pressure reduction is needed.
Built-in Flow Restriction
The integrated valve mechanism prevents excessive aqueous outflow, reducing the risk of early postoperative hypotony.
No Need for Flow-Modulating Sutures
Unlike non-valved implants, valved devices do not require ligatures, stents, or staged opening, simplifying the surgical process and postoperative care.
Shorter Surgical Time
The procedure is typically faster and technically less complex compared to non-valved implant surgeries that require meticulous flow control techniques.
Ideal for High-Risk Eyes
Valved implants are especially useful in -Neovascular glaucoma, Uveitic glaucoma, Post-traumatic eyes, and Eyes with thin sclera or poor healing capacity.
Reduced Early Complication Risk
Due to controlled early flow, there’s a lower incidence of choroidal detachment, flat anterior chamber, and hypotony maculopathy.
Superior Long-Term IOP Control
Non-valved implants typically provide lower and more sustained IOP compared to valved devices—especially beneficial in advanced or refractory glaucoma cases.
Larger Plate Surface Area
Devices like the Baerveldt (350 mm²) or AADI (350 mm²) have larger end plates, allowing greater surface area for filtration and more efficient aqueous absorption over time.
Lower Medication Dependence
Patients with non-valved implants are less likely to require long-term glaucoma medications compared to those with valved devices.
Fewer Mechanical Failures
Without internal valve components, non-valved implants have no risk of valve malfunction or blockage, leading to more reliable performance in the long term.
Greater Efficacy in Pediatric and Congenital Glaucoma
Non-valved devices are often favoured in children or complex congenital glaucoma due to their competent pressure-lowering effect.
More Cost-Effective Options Available
Ideal for Eyes Needing Lower Target Pressures
In cases where IOP must be reduced to single digits or low teens, non-valved implants are often more effective than valved devices.
RECENT NON-VALVED DEVICE
The Ahmed Clear Path is an innovative, newer non-valved drainage implant that offers a simplified surgical approach, effective pressure control, and potential reduction in medication dependence. Unlike the Ahmed Glaucoma Valve (AGV), which uses a mechanical valve to control flow and may risk hypotony, the Clear Path features a non-valved design for consistent outflow. Compared to the Aurolab Aqueous Drainage Implant (AADI), this is a cost-effective, non-valved alternative. The Clear Path offers easier implantation and improved flow dynamics due to its unique structure. Its ease of use, safety profile, and clinical effectiveness make it a preferred choice for refractory cases.
The tube shunts excess fluid from the front of the eye to a plate (positioned under the conjunctiva), where the fluid is absorbed gradually, helping to reduce intraocular pressure.
The procedure typically takes 45–90 minutes and is usually performed under local anaesthesia with sedation or general anaesthesia, depending on the patient’s condition.
You shouldn’t feel pain during the surgery due to anaesthesia. Some mild discomfort, foreign body sensation, watering, or redness is normal after surgery, but this usually improves within a few days.
Infection, bleeding, double vision, Hypotony (too low IOP), Tube blockage, Cataract progression are some of the complications expected after tube surgery. Most complications are manageable with medication or additionalprocedures if needed.
Yes, Possibly. Many patients require fewer medications after surgery, but some may still need drops to maintain target pressure, especially over time.
No, the implant is placed under the conjunctiva (the white part of the eye), so the tube and plates are generally not visible to others.
Sometimes, very rarely, the tube can become blocked or displaced. This may require surgical revision. Regular follow-up visits help detect and manage such issues early.
Most glaucoma drainage implants are designed to last a lifetime, although their effectiveness may gradually decline over time. Some patients may need additional treatments later on.
Yes. Glaucoma tube implants are MRI-safe and do not interfere with airport security or air travel.
No, it does not cure glaucoma, but it can help control intraocular pressure and prevent further vision loss. Regular monitoring is still necessary.
