What is it and Why do people have this test?

When patients have high pressure, it can be due to an imbalance between the amount of fluid produced in the eye and the amount that leaves the eye. When fluid leaves the eye, it exits through a part of the eye called the drainage angle. If the drainage angle is narrow or obstructed, fluid cannot easily leave and the internal eye pressure rises.

In order to examine your drainage angle, we perform a procedure called “Gonioscopy”. This allows us to examine the angle which is otherwise hidden from our view. The drainage angle is located under the edge of the opaque sclera (white part of the eye) where it turns into the clear cornea. For this procedure, which is performed at the biomicroscope, the eyes are anesthetized with drops and a gonioscopy lens is placed upon the cornea. This is a special lens with mirrors built into it through which we can view the drainage angle.

All patients with glaucoma will undergo gonioscopy when their disease is first being evaluated. In this way the doctor can differentiate between open angle glaucoma and closed angle glaucoma. The outcome of this will have a major impact upon the choice of treatment.

Gonioscopy will be repeated at various times during the course of treatment to make sure that the drainage angle has not narrowed and that there are no other obstructions to the outflow of fluid.

- Lawrence M. Hurvitz, M.D.