This surgery involves placement of a flexible tube inside the eye that drains aqueous humor, the fluid inside the eye, to an external reservoir. The Ahmed valve is a type of tube-shunt that has a valve to regulate the amount of fluid drained from the eye. This type of surgery is often performed in people with glaucoma resulting from diabetes or in people with corneal transplants. It can also be performed when a prior trabeculectomy has failed, or if a person has a high likelihood of forming scar tissue in the eye.
Tube-shunt surgery – How Well It Works Sixty to 85% of tube-shunt surgeries are successful in lowering eye pressure. Many people undergoing tube-shunt surgery require continued use of glaucoma medications in order to achieve sufficiently low eye pressures. Some people require additional treatment or surgery over time.
Tube-shunt surgery – What To Expect During & After Surgery Generally, tube-shunt surgery is performed on an outpatient basis. It is performed under local anesthesia in which medicine is administered intravenously to relax the patient. A numbing shot is administered under the eye to prevent pain and eye movements during surgery. The surgery takes about 30 minutes, although the whole pre and post-operative process may take a few hours.
Immediately after surgery, the eye is patched, and an eye shield, a hard covering, is placed over the eye. The doctor’s assistant will remove these the following day. Until this time the patient does not require any eye medications in the operated eye. On the day of surgery and for at least 2 weeks patients need to avoid any activity that might jar the eye, such as bending, lifting, or straining. Additionally, the eye shield should be worn at night for 2 weeks in order to avoid any external pressure on the eye.
On the day after surgery, it is normal for the vision to be extremely blurry after the eye patch and shield are removed. It is also normal for the eye pressure to range anywhere from zero to 30 on the first day after the operation, as it takes a few days for the filter to function optimally. At this time, instructions will be given regarding post-operative eye drops. For most patients this will include Pred Forte drops for 4-6 weeks and an antibiotic drop for 1-2 weeks. All other should be discontinued in the operated eye.
Post-operative visits will take place with the doctor about once a week for four weeks. If the tube is filtering excess fluid, injections may be necessary to regulate the pressure. Usually there is mild discomfort after tube-shunt surgery. This usually resolves as the stitches dissolve. . Pain is not typical and should be brought to the doctor’s attention immediately.
Tube-shunt surgery – Risks The most common problem after tube-shunt surgery is the formation of scar tissue that interferes with the proper function of the device. Other complications include, but are not limited to, blurring of the vision for several weeks (usual), worsening of pre-existing cataract, infection (rare), bleeding (rare), droopy eyelid (rare), corneal swelling (rare) and double vision (rare). In certain instances, the surgery can result in eye pressures that are too low. In these cases, injections to the eye or additional surgery may be necessary to regulate the pressure.