AQ Shunt

 

The AQ Shunt is a drainage device implanted in the outer layer of the eye to relieve over-pressurization caused by glaucoma. The objective of the AQ Shunt is to provide the world’s safest, most effective, long-term solution to glaucoma.

Glaucoma is one of the leading causes of blindness, affecting more than 67 million people worldwide. To understand glaucoma and its devastating effects, it is important to understand how the eye works. The front part of the eye is filled with a clear fluid (called aqueous humor) made by the ciliary body. Normal intraocular pressure (IOP) levels range from 12-15 mm Hg (millimeters of mercury). Positive pressure, generally above 6 mm Hg, is needed to keep the retina attached to the back of the eye and to nourish the cornea and lens which have no blood vessels. This fluid flows out the eye’s drainage system (trabecular mesh work of drainage canals around the outer edge of the iris). Production, flow, and drainage of this fluid is an active, continuous process. In most types of glaucoma, the eye’s drainage system becomes clogged so the fluid cannot drain. As the fluid builds up, it causes increased pressure inside the eye. Pressure above 21 mm Hg can be dangerous and glaucoma patients often have pressures well above 30 mm Hg. Left untreated, high pressure damages the optic nerve and can result in gradual or sudden blindness.

Unfortunately, this debilitating disease is currently neither preventable nor curable. The only treatment is to lower the pressure. As a first line of defense, topical medication, eye drops and oral medicines, are usually prescribed to help either increase the exit of fluid from the eye or decrease the production of fluid in the eye. Patients can expect to take one to four doses per day indefinitely to maintain proper pressure. This is an extremely inconvenient and expensive proposition for patients, and the drugs themselves have many side effects. "Studies have revealed that more than 40% of patients miss 10% of their doses, and 15% miss more than half. Skipping even a few doses can greatly increase the risk of visual loss" (Reuters Health, Dec 2001).

If drugs fail to control the pressure, surgical procedures are usually performed to cut through or remove tissue from the eye to allow increased outflow of aqueous humor. The common problem with all surgical procedures is the associated build-up of scar tissue which decreases fluid outflow, necessitating repeated surgeries. To overcome blockage caused by scar tissue formation, ophthalmologists may recommend a drainage (shunt) implant that has a tube connected to a plate. The tube end is inserted into the anterior chamber of the eye to keep the channel through the trabecular meshwork open. The plate end of the shunt is inserted between the sclera and the conjunctiva to create a pocket that when pressurized with aqueous fluid forms a blister-like (spherical) cavity called a bleb. A fibrous capsule forms around the cavity, allowing Aqueous humor to slowly vent through its walls and reduce the pressure inside the eye.

Conventional wisdom among shunt developers is that the spherical blister is a necessary structure to prevent excessive outflow of fluid. However, the blister causes significant complications, all due to the blister’s presence. The four leading complications with the use of shunt devices are initial hypotony (pressure too low), diplopia (double vision), choroidal involvement (vascu­lar supply to the retina becomes engorged with blood at the risk of bleeding and detachment) and fibrosis of the filtration capsule (the outer layer of the capsule becomes too thick to effectively vent fluid). These four vision threatening complications account for a published cumulative complication rate >60% of the total number of large-plate shunt surgeries! While millions are diagnosed with glaucoma, only about 0.05% per year are treated with shunt implants. Only after a patient has failed to respond to the drugs and also failed other surgical options is the patient considered for a shunt implant. Therefore, shunts are currently employed as a last resort to save the patient’s vision. The main impediment to widespread use of these implants is due to the compli­cations. We have overcome this problem by changing implant geometry.

Our patented AQ Shunt implant defies conventional wisdom, using split-tube geometry to make a more efficient cylindrical filtration capsule than the spherical blister capsules created by large tube-plate shunts

All photography provided by Jared Chambers

 
 

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