Glaucoma is a group of eye conditions that damage the optic nerve, a bundle of nerve fibers that connects the eye to the brain. This damage is often caused by abnormally high pressure inside the eye (intraocular pressure), but it can also occur with normal eye pressure. If left untreated, glaucoma can lead to irreversible vision loss and blindness.
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.
Regular monitoring and adherence to the treatment plan are essential for managing glaucoma and preserving vision.
