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Glaucoma Surgery

Surgery to relieve increased intraocular pressure is needed in animals with glaucoma where medical therapy alone will not treat the problem.

There is normally an equal rate of secretion of fluid into the eye and then drainage of the fluid out of the eye into the blood stream. In glaucoma the problem is usually continued secretion of fluid in the eye continues with little reduction while the drainage of fluid from inside the eye is reduced. Consequently the pressure in the eye rises damaging ocular structures.

If medications fail to increase the fluid outflow or reduce fluid secretion we have to use surgical techniques to overcome the pressure rise.

Most commonly we use a laser to selectively destroy some of the cells in the eye producing fluid. This technique can either be performed surgically inside the eye using a very small endoscope to view the cells being destroyed and to deliver the laser energy to the cell. Alternatively the laser can be applied to the outside of the eye (the sclera) over the area with the cells inside the eye and the destructive energy focused at the level of the cells. A freezing probe (cryosurgery probe) can be used to achieve the same effect.

Either approach does create inflammation in the eye and may increase the pressure in the even more for a few days after the surgery. To prevent this happening we use an implant into the front chamber of the eye to drain fluid in the days after the laser procedure. Various implants are available – most have been designed for human glaucoma surgery and modified for our needs in animals. Some of the implants have special valves attached which are sutured to the outside of the back part of the eye. The valve regulates the intraocular pressure.

If the implant or valve becomes plugged with inflammatory cells form the laser procedures we can inject a material into the front part of the eye to re-establish the implant patency. Should the valve become encapsulated in scar tissue any time after surgery we can re-operate to remove the scar and re-establish valve patency

No treatment for glaucoma is 100% successful. Most animals need some continued medical therapy even after surgery. These treatments do however offer some hope of continued vision in animals despite a difficult disease for all species.