Glaucoma is a leading cause of vision loss worldwide, but understanding how it affects the eye starts with a basic knowledge of eye anatomy. This disease mainly damages the optic nerve due to increased inner eye pressure, or intraocular pressure (IOP), often without noticeable symptoms in its early stages. By exploring the eye’s structure, the role of fluid drainage, and how glaucoma leads to vision loss, we can better understand why early detection and treatment are so important.*

The Eye’s Anatomy

The eye is a sophisticated organ designed to capture and process light. Specifically:

• The outermost layer, the sclera, provides structural support. 
• The cornea at the front acts as a protective, transparent window. 
• The iris, the colored part of the eye, controls how much light enters through the pupil. 
• Behind the iris, the lens focuses light onto the retina, which converts images into electrical signals. 
• These signals travel through the optic nerve, which transmits them to the brain for interpretation.

The fibers that form the optic nerve converge at the optic disc, a structure at the center of the retina. This area is particularly vulnerable to glaucoma-related damage, which can lead to vision impairment and loss over time.

The Eye’s Drainage and Pressure Regulation

The front part of the eye contains a clear fluid called aqueous humor, produced by the ciliary body. This fluid nourishes the eye and helps maintain its shape. It drains through the trabecular meshwork and other tiny canals, creating a balance between fluid production and outflow.

IOP depends on this delicate balance. A normal IOP ranges between 12 and 22 mmHg. If fluid drainage is obstructed, IOP increases, placing pressure on the optic nerve. Proper drainage is essential for maintaining healthy vision and preventing conditions like glaucoma.

How Glaucoma Causes Vision Loss

Glaucoma develops when the eye’s drainage system becomes inefficient, usually through some type of blockage, leading to fluid buildup and increased IOP. This pressure damages the delicate nerve fibers in the optic disc, causing it to develop a cupped shape—a key sign of glaucoma that doctors look for during eye exams.

Initially, glaucoma affects peripheral (side) vision, making early symptoms hard to detect. Over time, vision loss can progress to central vision. Once lost, sight cannot be restored. While high IOP is a major risk factor, some people develop glaucoma even with normal pressure levels, indicating that other underlying mechanisms are also at play.

Because glaucoma often develops gradually and painlessly, regular eye exams are essential for early detection. If glaucoma is caught early, treatments such as eye drops, laser therapy, or surgery can help maintain vision and slow the disease’s progression.

*Glaucoma Research Foundation. (n.d.). Eye Anatomy. https://glaucoma.org/articles/eye-anatomy 

Responsum Health closely vets all sources to ensure that we always provide you with high-quality, reliable information. We do not, however, endorse or recommend any specific providers, treatments, or products, and the use of a given source does not imply an endorsement of any provider, treatment, medication, or procedure discussed within