Understanding Glaucoma: Causes, Symptoms, and Treatment Options

Posted by: Philadelphia Eye Associates in Eye Health on February 20, 2026

Written by Ommay Farah and edited by Brad Feldman, MD

Glaucoma is one of the world’s most common eye diseases. Glaucoma is an umbrella term for a set of diseases that cause characteristic damage to the optic nerve. The optic nerve connects the eye to the brain and, similar to the spinal cord, cannot recover from damage. Therefore, vision loss from glaucoma is irreversible. In most cases of uncontrolled glaucoma, individuals will lose their peripheral vision before losing their central vision.  

The internal pressure of the eye, which keeps it inflated like a grape rather than shrunken like a raisin, is critical in glaucoma. In most cases of glaucoma, eye pressure, termed intraocular pressure, is too high for the health of the optic nerve.  

Intraocular pressure is maintained by the aqueous humor, a fluid produced by part of the eye called the ciliary body. As the ciliary body produces more aqueous humor, some aqueous humor needs to drain out of the eye through the drainage pipe of the eye called the trabecular meshwork. This drain often becomes clogged in individuals with glaucoma and can lead to an increase in intraocular pressure. This pressure can then lead to optic nerve damage in the form of optic nerve cupping.   

The optic nerve, which is somewhat hollowed out, consists of two parts and can be thought of as a doughnut. The inner region of this doughnut is the optic cup, and the outer dough area is the optic disc. The same way we want a doughnut with the right dough to hole ratio, our optic nerve has an optimal cup to disc ratio. The irregular enlargement of the optic cup is termed optic nerve cupping. The glaucoma leads to cupping and optic nerve damage.  

Our optic nerve plays a key role in sight. It transmits visual signals from our eyes to the brain, specifically the visual cortex, which allows us to perceive the environment around us. This is why damage to the optic nerve can lead to vision loss. 

Glaucoma is diagnosed by analyzing an individual’s optic nerve, intraocular pressure, and peripheral vision deficits. A machine called the Optical Coherence Tomography (OCT) can be used to image the optic nerve and assess optic nerve cupping. Applanation tonometry is used to monitor intraocular pressure, and a visual field machine or automated perimetry machine is used to assess peripheral vision loss.   

A glaucoma diagnosis is managed by close observation, eye drops, or surgical procedures. The eye drops that are used by individuals with glaucoma work to lower the intraocular pressure, thus limiting damage to the optic nerve. 

The two primary types of Glaucoma are Primary Open Angle Glaucoma (POAG) and Angle Closure Glaucoma. In POAG, the drainage system of the eye becomes less efficient as the trabecular meshwork starts to become blocked.Contrasted to this, in Angle Closure Glaucoma the drainage system is partially or completely blocked, thereby limiting fluid drainage from the eye. POAG can often present without symptoms whereas Angle Closure Glaucoma presents with symptoms such as eye pain, headaches, nausea, and increased pressure around the eyes.  

The primary treatments to POAG are often eye drops or Selective Laser Trabeculoplasty (SLT).  In SLT laser energy, applied to the trabecular meshwork, helps to increase the amount of fluid drained from the eye. The full benefits of the SLT procedure may take a couple of months to develop.  

Individuals with Acute or Intermittent Angle Closure Glaucoma often require immediate medical attention. One procedure that is used to treat these individuals is Laser Peripheral Iridotomy (LPI). In this procedure, a laser is used to create a tiny hole in the iris. This hole provides an alternate pathway for fluid to move within the eye and decreases the blockage of the trabecular meshwork. This procedure may provide an immediate decrease in the intraocular pressure for individuals experiencing Acute Angle Closure Glaucoma.  

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1. National Eye Institute. “Types of glaucoma.” National Institutes of Health.
https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/glaucoma/types-glaucoma

2. Mayo Clinic. “Glaucoma: Symptoms and causes.” https://www.mayoclinic.org/diseases-conditions/glaucoma/symptoms-causes/syc-20372839

3. Cleveland Clinic. “Open-angle glaucoma.” https://my.clevelandclinic.org/health/diseases/open-angle-glaucoma