Glaucoma, which is the second leading cause of blindness in the world, is an optic disease which damages the optic nerves because of the pressure it makes on the eye by overproduction of a fluid called aqueous humor.
Normally, glaucoma is treated with a standard surgery called "trabeculectomy". But in certain cases, where this surgery has a poor chance of success, another option is considered to drain away the surplus eye water. This surgery is done by implanting a silicon tube, called Ahmed Valve, into the front part of the eye to drain out the excess water and lower the pressure it makes on eye. The fluid is then naturally absorbed by the surrounding tissue.
Trabeculoplasty is another procedure to treat glaucoma with laser. However, it is not the best option for the cases which ahmed valve implantation is recommended.