Causes
The primary cause of glaucoma is often elevated intraocular pressure (IOP), which results from a buildup of fluid (aqueous humor) in the front part of the eye. This fluid normally drains out through a mesh-like channel called the trabecular meshwork. When this drainage system doesn't work properly, fluid accumulates, increasing pressure inside the eye. Types of glaucoma and their causes include:- Primary Open-Angle Glaucoma (POAG): This is the most common type. The drainage angle of the eye (where the iris and cornea meet) is open, but the trabecular meshwork is not draining fluid effectively. The cause is often unknown, but it's linked to genetics and age.
- Angle-Closure Glaucoma (Acute or Chronic): This type occurs when the drainage angle is blocked, either suddenly (acute) or gradually (chronic), preventing fluid from leaving the eye. This can happen if the iris bulges forward, narrowing or blocking the angle.
- Normal-Tension Glaucoma: In this type, optic nerve damage occurs even with normal eye pressure. It's thought to be related to fragile optic nerves or reduced blood flow to the optic nerve.
- Secondary Glaucoma: This type develops as a complication of another medical condition or factor, such as:
- Eye injury or trauma
- Certain medications (e.g., long-term corticosteroid use)
- Other eye conditions (e.g., inflammation, tumors, advanced cataracts)
- Systemic diseases (e.g., diabetes, high blood pressure)
- Congenital Glaucoma: A rare form present at birth or developing in early childhood due to abnormal development of the eye's drainage system.
Symptoms
Glaucoma is often called the "silent thief of sight" because, especially in its most common form (POAG), it typically has no symptoms in its early stages. Vision loss usually begins with peripheral (side) vision, which often goes unnoticed until significant damage has occurred. Symptoms, if present, can include:- Primary Open-Angle Glaucoma:
- Usually no symptoms in early stages.
- Gradual loss of peripheral vision.
- Tunnel vision in advanced stages.
- Acute Angle-Closure Glaucoma (a medical emergency):
- Sudden, severe eye pain.
- Blurred vision.
- Halos around lights.
- Redness of the eye.
- Nausea and vomiting.
- Other types of glaucoma: Symptoms may vary depending on the specific type and underlying cause.
Diagnosis
Regular comprehensive eye examinations are crucial for early detection of glaucoma, especially for individuals at higher risk. Diagnosis typically involves:- Tonometry: Measures intraocular pressure (IOP).
- Ophthalmoscopy (Dilated Eye Exam): The doctor examines the optic nerve for signs of damage, such as cupping (an indentation in the optic nerve head).
- Perimetry (Visual Field Test): Measures peripheral vision to detect any blind spots caused by optic nerve damage.
- Gonioscopy: Examines the drainage angle of the eye to determine if it's open or closed.
- Pachymetry: Measures the thickness of the cornea, which can influence IOP readings.
- Optical Coherence Tomography (OCT): Provides detailed images of the optic nerve and retinal nerve fiber layer to detect early changes.
Treatment
Glaucoma damage is irreversible, so treatment focuses on preventing further vision loss by lowering intraocular pressure.- Medications (Eye Drops): These are the most common initial treatment.
- Prostaglandin analogs: Increase fluid outflow (e.g., latanoprost, travoprost).
- Beta-blockers: Decrease fluid production (e.g., timolol).
- Alpha-adrenergic agonists: Decrease fluid production and increase outflow (e.g., brimonidine).
- Carbonic anhydrase inhibitors: Decrease fluid production (e.g., dorzolamide, brinzolamide).
- Rho kinase inhibitors: Increase fluid outflow (e.g., netarsudil).
- Combination drops: Combine two different medications.
- Laser Treatment:
- Selective Laser Trabeculoplasty (SLT): For open-angle glaucoma, a laser is used to improve drainage through the trabecular meshwork.
- Laser Peripheral Iridotomy (LPI): For angle-closure glaucoma, a small hole is made in the iris to open the drainage angle.
- Surgery: If eye drops or laser treatment are not sufficient, surgical procedures may be performed.
- Trabeculectomy: Creates a new drainage pathway for fluid to leave the eye.
- Glaucoma drainage devices (shunts): Small tubes are implanted to drain fluid from the eye.
- Minimally Invasive Glaucoma Surgery (MIGS): A newer category of procedures that use tiny devices to improve fluid outflow, often performed in conjunction with cataract surgery.
Keeping Glaucoma Treatment Working
Glaucoma treatment fails far more often from drops that are missed or poorly instilled than from drops that do not work. The pressure target is individual, the damage is silent, and the only proof that treatment is working is a visual field and nerve scan that stays the same year after year.
Getting the drop in, and keeping it there
One drop is enough; a second washes the first away. Close the eye for a minute afterward and press gently on the inner corner against the nose to keep it out of the bloodstream. Wait at least five minutes between different drops, and use any gel last. A prostaglandin drop such as latanoprost works once a day at bedtime, and evening timing matters because pressure runs highest overnight and in the early morning.
Side effects worth knowing before they alarm you
Latanoprost lengthens and darkens the lashes, can slowly deepen the color of a hazel or green iris, and darkens the skin around the eye; these are cosmetic and expected. Timolol and other beta-blocker drops are absorbed enough to slow the heart and narrow the airways, so they are avoided in asthma, COPD, and slow heart rhythms.
Laser first is now a reasonable choice
Selective laser trabeculoplasty lowers pressure about as well as a first drop, needs no daily adherence, and can be repeated, which is why many ophthalmologists now offer it before drops rather than after them. Combined cataract removal and minimally invasive glaucoma surgery is an efficient route when cataracts also need treatment.
Medications that raise pressure or close the angle
Steroids in any form, including nasal sprays, inhalers, skin creams, and joint injections, raise eye pressure in susceptible people, so anyone with glaucoma on long-term prednisone or a steroid inhaler needs pressure checks. In narrow-angle eyes, decongestants, motion sickness pills, older antihistamines, and bladder medications such as oxybutynin can trigger angle closure; ask before starting them. Sudden severe eye pain with a red eye, halos, blurred vision, and nausea is acute angle closure and needs an emergency room the same hour.
Follow-up, driving, and family
Pressure checks every few months and visual field and nerve fiber scans once or twice a year are how progression is caught while there is still vision to save; a stable field is the goal, not a particular number. Loss of side vision affects driving before it affects reading, which our driving safety for older adults guide addresses. First-degree relatives, and Black and Hispanic adults, carry a higher risk and benefit from earlier dilated exams. Diabetes and sleep apnea raise risk as well. Our ophthalmology team coordinates monitoring, and our silent thief of sight article covers screening. The National Eye Institute and the Glaucoma Research Foundation publish patient guidance on drops and procedures.
If you have glaucoma and have missed drops or a follow-up in the past year, schedule a visit.