A leading cause of irreversible vision loss for people aged 60 and older, glaucoma is a serious eye condition affecting more than an estimated 3 million people in the United States. It is typically marked by an abnormal buildup of fluid inside the eye which increases intraocular pressure. This elevated pressure in turn can damage the optic nerve, the pathway through which the images are transmitted to the brain for processing. Unchecked, the condition can lead to irreversible vision loss.
In its early stages of development, glaucoma typically has few symptoms, making it difficult to detect before serious damage has been done. In fact, some estimates suggest that as many as 50 percent of Americans with glaucoma are unaware they have the condition. This underscores the importance of having routine glaucoma screenings if you meet certain risk factors.
Generally speaking, glaucoma is an age-related eye condition. There are exceptions, such as glaucoma caused by trauma or infection, but most cases affect people over the age of 40.
African Americans have a higher incidence rate of glaucoma than Caucasians. In fact, glaucoma-related blindness is considerably more prevalent (up to six times the rate) among African Americans. Mexican Americans also face an increased risk of glaucoma, though not comparable with the incidence rate for African Americans.
It is an inherited disease, meaning that if you have a family history of glaucoma, you are at increased risk. Additional risk factors include thin corneas or people with thinning of the optic nerve, general health conditions such as diabetes, obesity and circulatory problems, and other eye issues like extreme myopia and hyperopia.
If you are over 40 and have one or more risk factors for glaucoma, you should be screened every one or two years. Early detection is key to preventing significant vision loss.
Although glaucoma is marked primarily by increased ocular pressure, not all patients have increased pressure. Indeed, in Japan and other parts of Asia, most patients have normal pressure. Normal pressure is generally considered above 12 and below 21 mmHg. Further, it is still unknown whether elevated pressure appears only in the more advanced disease state and remains normal (undetected) during the initial stages. As such, diagnosis requires more than simply measuring the pressure inside the eye. A complete eye exam is required in order to conclusively diagnose glaucoma.
During your comprehensive glaucoma screening, an ophthalmologist will inspect a range of things, including:
- Intraocular pressure
- Corneal thickness
- Peripheral vision
- Optic nerve health
- The drainage angle of the eye
Newer diagnostic techniques include high resolution imaging of the back of the eye and improved technology for testing central vision, such as contrast sensitivity.
Open-angle vs. Angle-closure
There are two categories of glaucoma: open-angle and angle-closure.
Open-angle glaucoma: The most common type of glaucoma, primary open-angle develops slowly and asymptomatically. The “angle” refers to the drainage angle for discharging watery fluid from the eye. A healthy drainage angle allows fluid to flow freely from the eye, helping to maintain normalized pressure. In the case of open-angle glaucoma, fluid is not getting adequately drained from the eye and pressure builds.
Angle-closure glaucoma: Also called “closed-angle” or “narrow-angle,” it is a far less common type of glaucoma. Unlike the slow, asymptomatic development of open-angle glaucoma, angle-closure is an acute form of the condition, meaning that the disease progresses quickly. This is caused when the drainage angle is completely blocked, and the fluid cannot drain from the eye, leading to a rapid increase in pressure. Also, unlike the open angle variety which is asymptomatic in the early stages, closed-angle glaucoma can be painful due to the high pressure levels in the eye. Angle-closure glaucoma is often an eye emergency requiring immediate medical attention to relieve the pain and to prevent blindness.
Signs and Symptoms
Given the asymptomatic development of early-stage glaucoma, the disease often progresses significantly before it is detected. For many years, it was believed that glaucoma affected primarily peripheral vision and central vision was left unharmed until very late in the disease. Contrary to this dogma, research now shows that loss of peripheral vision is not an early indication of the disease, and that the full range of vision (peripheral and central) is often affected. Further, the visual field tests are not sensitive to early vision losses. By the time glaucoma is detected by a peripheral field test in many patients, more than half of the optic nerve fibers are damaged or have perished. Research is ongoing to perfect better tests for central vision that can detect the disease in earlier stages.
Symptoms of the disease can include:
- Blurred vision
- Reduced ability to see in low contrast situations, like a garage at night
- Eye pain
- Eye redness
- Vision loss
As noted earlier, an acute case of glaucoma, often associated with angle-closure, may cause severe eye pain (or pain in the forehead), nausea and vomiting, in addition to the other symptoms listed.
Unfortunately there is no curative treatment for glaucoma vision loss. Treatment is therefore focused on slowing the progression of the disease and limiting further damage. Eye drops or pills used to lower the eye pressure are the most commonly used treatments. Daily use can help to lower intraocular pressure and minimize optic nerve damage.
In some cases laser surgery may be used to improve the fluid drainage from the eye and reduce pressure. This type of procedure is called trabeculoplasty. A more aggressive procedure, referred to as trabeculectomy, requires the surgeon to use a scalpel as opposed to a laser to open the drainage channels. More recently, a procedure called MIGs has been developed which incorporates the use of small implants or stents inserted by the surgeon into the drainage channel to improve outflow. For angle-closure patients, iridotomy is used to create microscopic holes in the iris to relieve the blockage and help flow to the drainage angle.
The effects of treatment range depending on how advanced glaucoma is and other factors including the health (both vision and general) of the patient.