Glaucoma: Causes, Symptoms, Types, and Treatment

Glaucoma occurs due to optic nerve damage. The nerve gradually loses function, causing blind spots to develop in the visual field. The exact cause of this is unknown, but it is believed that nerve damage usually occurs due to increased pressure in the eyes.

Eye pressure increases due to the build-up of internal fluid (aqueous humor) that flows throughout the eyes. The fluid drains through a tissue called the trabecular meshwork at the angle where the iris (colored part of the eye) and cornea meet. If there is an overproduction of the fluid or if the fluid doesn’t drain properly, the fluid builds up causing increased eye pressure.

Risk factors of glaucoma:

• High intraocular pressure (eye pressure)
• Age over 60 years
• Black, Asian, or Hispanic races 
• Family history of glaucoma
• Diabetes
• Heart disease
• Hypertension (high blood pressure)
• Sickle cell anemia
• Corneas that are thin in the center
• Myopia (Extreme nearsightedness) or hypermetropia (farsightedness)
• Trauma
• History of eye surgery
• Taking corticosteroid medications, especially eye drops, for a long time

There are several types of glaucoma. These include:

• Open-angle glaucoma: This is the most common form of the disease. The drainage angle formed by the cornea and iris remains open, but the trabecular meshwork is partially blocked, causing eye pressure to gradually increase. It may be asymptomatic until vision loss occurs.
• Angle-closure glaucoma: This is also called closed-angle glaucoma. It occurs when the iris bulges, narrowing or blocking the drainage angle formed by the cornea and iris. Angle-closure glaucoma may occur suddenly (acute angle-closure glaucoma), which is a medical emergency, or gradually (chronic angle-closure glaucoma).
• Normal-tension glaucoma: The optic nerve gets damaged despite the eye pressure being normal. The exact cause is unknown. It could be due to optic nerve sensitivity or decreased blood supply to the optic nerve.
• Glaucoma in children: It may be caused by drainage blocks or a developmental eye abnormality.
• Pigmentary glaucoma: Activities such as running, jogging, or other sports can cause pigment granules from the iris to dislodge and deposit in the trabecular meshwork, blocking fluid drainage and causing increased eye pressure.

The signs and symptoms of glaucoma vary depending on the type and stage of your condition:

Open-angle glaucoma:

• Patchy blind spots on the peripheral (sides) or central vision, usually in both the eyes
• Tunnel vision in the advanced stages

Acute angle-closure glaucoma:

• Severe headache and eye pain
• Nausea and vomiting
• Blurring of vision
• Halos around lights
• Redness of eyes

The damage caused by glaucoma can't be reversed. However, early treatment and regular follow-ups can help delay the progression or prevent vision loss, especially in the early stages. Treatment options include:

Prescription eye drops:

• Prostaglandins: These increase the drainage of the aqueous humor (fluid in the eye), resulting in decreased eye pressure.
• Beta-blockers: These reduce the production of fluid in the eyes, resulting in decreased eye pressure.
• Alpha-adrenergic agonists: These reduce the production of eye fluid and increase the drainage of fluid. 
• Carbonic anhydrase inhibitors: These reduce the production of fluid in the eyes. 
• Rho-kinase inhibitor: This suppresses the enzyme, rho kinase, responsible for the fluid increase. 
• Miotic or cholinergic agents: These increase the drainage of eye fluid. 

Oral medications: Oral medications such as carbonic anhydrase inhibitor may be prescribed.

Surgery and other therapies:

• Laser therapy: Laser trabeculoplasty may be done for open-angle glaucoma. A small laser beam is used to open clogged channels in the trabecular meshwork.
• Trabeculectomy: A part of the trabecular meshwork is removed.
• Drainage tubes: A small tube/shunt is inserted in the eye to drain excess fluid and lower eye pressure.
• Minimally invasive glaucoma surgery (MIGS): These procedures reduce eye pressure and usually require less postoperative care and have less risk than trabeculectomy or installing a drainage device. They can be combined with cataract surgery. 

Treating acute angle-closure glaucoma: This is a medical emergency and usually will require both emergency medical and laser or other surgical procedures. Laser peripheral iridotomy is a procedure in which a small opening is created in the iris, resulting in improved drainage.

Treatment of underlying medical conditions: Treatment of medical conditions such as diabetes and hypertension that make you prone to glaucoma.