Glaucoma Awareness Month

January is Glaucoma Awareness Month, so I think we all know what this month's post is about. According to the World Health Organization (WHO), glaucoma is the second leading cause of blindness world-wide (1), and Open Angle Glaucoma affects more than 2 million people in the US alone (2).

A cupcake rendition of the optic nerve

What is glaucoma?
Glaucoma is a group of diseases that damage the optic nerve. The optic nerve is like a cable, made of about 1 million nerve fibers, that sends signals from the retina (the tissue that lines the back of the eye) to the brain. When the optic nerve is damaged, permanent vision loss results.

There are many types of glaucoma, the most common of which is Primary Open Angle Glaucoma (POAG). In most cases of glaucoma (but not all!), the pressure within the eye is higher than normal. The eye has a clear fluid, called aqueous humor, that circulates in the front part of the eye and flows out through a structure called the angle (here is a good visual). Through various mechanisms, this fluid may not flow out of the front of the eye properly, leading to elevated eye pressure, or intraocular pressure (IOP). High IOP can slowly damage the optic nerve over time.


How do I know if I have glaucoma?
Most cases of glaucoma do not have symptoms early on. Peripheral vision loss occurs, but by the time you notice this, the disease is substantially progressed and significant, permanent vision loss has occurred. Since there really aren't symptoms to watch out for, early detection during yearly eye exams is key.

There are some factors that increase risk for glaucoma:

• a family history of glaucoma
• being of African-American or Hispanic descent
• older age 
• high eye pressure
• thin corneas

*Note: People of any age, race, or eye pressure level can have glaucoma.

Glaucoma can also result from another disease or condition, like eye trauma or inflammation. Additionally, some studies have shown a relationship between glaucoma and conditions of altered blood flow (ie: sleep apnea, diabetes, migraines, high or low blood pressure).

How is glaucoma diagnosed?
Glaucoma is a complex disease, so many areas need to be looked at to obtain an appropriate diagnosis and management plan. Some procedures that may be involved in the diagnostic/management process:

• Tonometry: A tonometer probe is used to gently measure intraocular pressure (IOP) in millimeters of mercury. "Normal" IOP is typically under 21mmHg, though you can have glaucoma with normal IOPs. You can also have higher than normal IOPs without having damage to the optic nerve.
• Perimetry/Visual Field Testing: A visual field test assesses the function of the optic nerve. When enough nerve fibers are damaged, you develop missing spots in your field of vision. The visual field test picks up these missing spots early on (far, far sooner than you would pick them up on your own). 
• Pachymetry: This test measures the thickness of the central part of your cornea. Thinner corneas not only underestimate eye pressure, but they have also been shown to be a risk factor for glaucoma progression (3,4).
• Gonioscopy: A lens with mirrors is placed on the eye, allowing your eye doctor to get a closer look at the drainage angle of the eye. 
• Dilated fundus exam: Your eye doctor uses a high-powered lens and a slit lamp to evaluate the health of the optic nerve, best viewed through a dilated pupil. Your eye doctor may choose to take photos as well, similar to the one seen below.
• GDx, HRT, OCT: In addition to directly evaluating the optic nerve, there are scans that can be used to image the optic nerve and further assess its structure. These scans give information on the amount of optic nerve tissue loss and the rate of nerve fiber thinning. The structural defects on the optic nerve should correlate with the functional defects in the visual field.

End-stage glaucoma

How is glaucoma treated and managed?
There is no cure for glaucoma, but the damage it causes can be slowed by the use of medications and/or surgery. Of the risk factors mentioned, the only one we can control is eye pressure, so that is the focus of treatment. The goal is to increase outflow of the fluid in the eye, or decrease production of that fluid, or both. This can be achieved using medications (typically eye drops), laser procedures, or glaucoma surgery. The course of treatment depends on both the type and severity of glaucoma.

What about marijuana?  I've been asked this question more than once. Marijuana is not a legitimate form of glaucoma therapy. Yes, a study from 1971 showed that smoking marijuana reduces eye pressure, but only for about 3-4 hours after smoking (5). Glaucoma management requires around-the-clock IOP control. Drops and/or surgery are much more effective at lowering IOP over the long-run and are less detrimental to your health, so I do not consider marijuana an appropriate glaucoma treatment.


What is the prognosis?
Left untreated or uncontrolled, glaucoma can lead to blindness. But the good news is it can be diagnosed on routine eye exams, and it is treatable. See your optometrist at least every 1-2 years, or more frequently if warranted. This is especially important for those with several risk factors. If you are diagnosed with glaucoma, it is important that you are compliant with the treatment and follow-up regimens outlined by your eye doctor. Effective management requires a team effort between you and your eye doctor.


CliffsNotes: Glaucoma is a leading cause of blindness. Know the risk factors and see your eye doctor regularly!

Additional Recommended Resources:

• Glaucoma Research Foundation
• AOA: Glaucoma
• NEI: Glaucoma
• All About Vision: Glaucoma