Implants For The Treatment of Glaucoma

The answer to Glaucoma treatment when prescription eye drops are not successful. Between the backside of the cornea (clear covering over the front of the eye) and the lens, your eye is getting an internal bath.

The clear “bathwater” is called the aqueous humor (or simply aqueous). Its function is to nourish the eye’s interior structures. The aqueous circulates between the iris and lens, through the pupil, and into the area between the iris and cornea. Then it drains out at the site where the iris and cornea meet (the angle). The angle is made up of a net-like structure called the trabecular meshwork (or trabeculum). From the trabeculum, the aqueous flows into a canal and thence to the blood stream.

Aqueous production and flow is a constant process. Unfortunately, it is not always flawless. Sometimes it’s a case of an over-production of aqueous, and the drainage can’t keep up. Other times the problem lies in the trabeculum, where the structure is inadequate or faulty, and outflow is slowed. Whatever the cause, the result is the same: pressure builds up in the eye from the excess fluid.

While the aqueous humor is physically limited to the anterior chamber, the effects of increased pressure inside the eye (intraocular pressure, or IOP) is not. In some cases, the pressure builds up to the point where ocular structures are damaged. Like a hose with a knot in it, the weakest area is the spot where destruction will occur. In the eye, the most vulnerable area is the optic nerve. The increased IOP is transferred back through the eye, and nerve damage may result.

Nerve damage from the high pressure typically occurs in pretty much the same way in every eye. The pattern is so classic that it has become a cornerstone in diagnosing the disease in which elevated IOP has caused nerve damage and vision loss: glaucoma. Glaucoma is usually treated first with medication. One drop twice a day may be all that is necessary to restore equilibrium and prevent further damage. If medication is not successful, surgery may be needed. One such procedure includes another type of implant, the drainage valve or filtering implant.

The filtering implant has two parts. The first is a tiny tube, called a seton, which is inserted into the anterior chamber. The second part is a plastic plate which is sutured into place between the sclera (white of the eye) and conjunctiva (membrane that covers the sclera). The seton conducts aqueous out of the anterior chamber. The plate keeps a drainage reservoir open to receive the excess fluid. This is especially useful in patients who tend to form scar tissue that would close off a reservoir without an implant.