Tonometry is a test to measure the pressure inside your eyes, or intraocular eye pressure (IOP). High eye pressure can damage the delicate nerve fibers in the back of your eye, and can sometimes result in blindness.

Elevated eye pressure isn't directly related to macular degeneration, but it's performed to rule out other conditions, like glaucoma. This is important so that it can be determined for sure if vision loss is coming from a disease of the macular or other parts of the eye.