Glaucoma is a medical condition that is often referred to as the 'silent thief of sight'. For many people it causes no pain or discomfort. Open angle glaucoma occurs because the pressure in the eye increases. Pressure increases if a structure called the ciliary body produces too much fluid. The fluid flows to a specific area of the eye called the trabecular meshwork. The meshwork looks like a sieve-like structure. Aqueous fluid drains out of the eye through this system. Over production or insufficient drainage causes an imbalance in the eyes ability to regulate its pressure. Although invisible to the naked eye, this pressure can cause damage to the back of the eye at the optic nerve. Left undetected, the rise in eye pressure damages the optic nerve. Your eye-care practitioner may use a special retinal camera to photograph your optic nerve for future reference. Damage to the optic nerve generally occurs slowly. Your practitioner will will use a number of different tests and techniques to detect glaucoma at its earliest stage.