Glaucoma is a group of chronic and progressive eye diseases that gradually damage the optic nerve. Essential for good vision, the optic nerve transmits electrical signals from the light-sensitive retina to the brain. Usually, glaucoma-related vision loss begins at the very outer edges of the visual field, then slowly begins to impact central vision.
The most frequently diagnosed type of glaucoma is open-angle glaucoma. Other, less common types include acute angle-closure glaucoma, normal-tension glaucoma, and pigmentary glaucoma.
What Are the Signs of Glaucoma?
After the optic nerve is damaged, it can take months or years for noticeable symptoms to develop. Because many types of glaucoma do not produce early warning signs, the condition is sometimes referred to as the “silent blinder.”
When symptoms do occur, they can vary depending on the type and stage of the condition:
- Open-angle glaucoma – Patchy blind spots in peripheral vision
- Acute angle-closure glaucoma – Sudden and severe eye pain, headaches, nausea and vomiting, blurred vision, and rainbow-like halos around lights
- Normal-tension glaucoma – Blurred vision that gradually worsens
- Pigmentary glaucoma – Blurred vision during intense physical activities
What Causes Glaucoma?
In many cases, glaucoma is caused by excessive pressure inside the eye (intraocular pressure), which can result from a problem with the eye’s drainage system. When fluid cannot freely drain from the eye, it may build up at the front of the eye, increase intraocular pressure, and ultimately damage the optic nerve.
The causes of glaucoma can vary based on its type:
- Open-angle glaucoma – Develops as tiny deposits build up in the eye’s drainage canals
- Acute angle-closure glaucoma – Occurs when the angle between the iris (colored part of the eye that controls light exposure) and cornea (clear outer part of the eye) is too narrow
- Normal-tension glaucoma – Affects people with normal intraocular pressure for unknown reasons
- Pigmentary glaucoma – Develops when pigment fragments flake off the iris and enter the clear fluid between the lens and the cornea (aqueous humor)
What Are the Risk Factors for Glaucoma?
Glaucoma can develop at any age, but it is most common in adults 60 and older. Diabetes significantly increases the risk of glaucoma due to a complication known as diabetic retinopathy, which causes abnormal blood vessels to grow out of the retina and prevents fluid from properly draining from the eye.
In addition to age and diabetes, other risk factors for glaucoma include:
- A family history of glaucoma
- High blood pressure
- Long-term corticosteroid use
- Nearsightedness (increases the risk of open-angle glaucoma)
- Farsightedness (increases the risk of closed-angle glaucoma)
- A previous eye injury
- Previous eye surgery
How Is Glaucoma Diagnosed?
Like many other eye diseases, glaucoma can be detected during a comprehensive eye exam, which may include:
- A tonometry test to measure intraocular pressure
- A dilated eye exam or imaging test to check for optic nerve damage
- A visual field test to check for areas of vision loss
- A pachymetry to measure corneal thickness
- A gonioscopy to inspect the eye’s drainage angle
How Can Glaucoma Be Prevented?
The key to preventing glaucoma-related vision loss is detecting the condition early. Toward that end, many experts recommend having a routine eye exam and glaucoma test performed by an ophthalmologist at the following frequencies:
- Every 1 to 2 years after age 35 for high-risk individuals
- Every 2 to 4 years before age 40
- Every 1 to 3 years between ages 40 and 54
- Every 1 to 2 years between ages 55 to 64
- Every 6 months to 12 months after age 65
How Is Glaucoma Treated?
To lower intraocular pressure, an ophthalmologist may prescribe eye drops, such as:
- Prostaglandins – Increase the outflow of eye fluid
- Beta-blockers – Reduce the production of eye fluid
- Alpha-adrenergic agonists – Reduce the production of eye fluid and increase the outflow of eye fluid
- Carbonic anhydrase inhibitors – Reduce the production of eye fluid
- Rho kinase inhibitors – Suppress the rho kinase enzymes responsible for eye fluid production
- Miotic or cholinergic agents – Reduce the production of eye fluid
If eye drops do not sufficiently lower intraocular pressure, an ophthalmologist may prescribe an oral medication, such as a carbonic anhydrase inhibitor in pill form, to further reduce the production of eye fluid.
Other treatment options for glaucoma include laser-assisted and minimally invasive surgical procedures, such as:
- Micro-invasive glaucoma surgery (MIGS) with iStent© – Often performed during cataract surgery, MIGS involves the implantation of a tiny titanium device at two sites in the front of the eye to create two bypasses for the outflow of eye fluid through the eye’s natural drainage system.
- Selective laser trabeculoplasty (SLT) – Using short pulses of low-energy light, an ophthalmologist targets the pigment in specific cells of the affected eye. In response, the body’s natural healing mechanisms rebuild the cells. The rebuilding process improves eye drainage and lowers intraocular pressure.
- Laser peripheral iridotomy (LPI) – Using a laser, the surgeon makes a tiny opening in the iris to widen the pathway to the drain of the eye.
- Trabeculectomy – The surgeon makes a tiny opening underneath the upper eyelid to serve as a drainage point for excess eye fluid.
- Drainage tubes – Tiny prosthetic devices are implanted in the eye to help drain eye fluid.
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