iStents are used as a treatment for glaucoma and, in children, NLD (nasolacrimal duct) obstructions. Stents are very small tubes usually made of plastic, fabric, or metal, which are surgically inserted to relieve obstructions and keep a path open so blood or other fluids can pass. Stenting to help treat glaucoma is used in combination with cataract surgery to reduce pressure inside the eye in certain adult patients who have mild or moderate open-angle glaucoma. Clear fluid in a healthy eye flows freely through the front chamber of the eye and drains out through a mesh of tissue and exit via into a canal at the edge of iris and cornea. If the meshwork becomes blocked or drains slowly, pressure builds up inside the eye to a level that may cause vision loss. A stent creates an opening to allow better drainage. In a healthy child, the nasolacrimal duct allows tears to exit the eye by draining into the nasal passages. In NLD, that duct is blocked or did not open at birth. NLD obstruction usually opens spontaneously by age 12 months. If it cannot be treated with other therapies, if anatomic abnormalities are present or the obstruction is tight, a silicone stent may be placed with the child under general anesthesia.