Glaucoma is the leading cause of irreversible blindness in the world and the United States.
The number of people with glaucoma worldwide is estimated to be over 70 million and is expected to increase to over 110 million by 2040. It currently affects more than 3 million people in the United States and is the leading cause of blindness in both African American and Hispanic populations. This is despite the fact of a low overall prevalence of 3.5 percent.
Glaucoma belongs to a class of eye diseases known as optic neuropathy. There are two main types of glaucoma: open angle and narrow or closed angle. The “angle” is the opening where the fluid drains from the eye. In narrow angle, the channel is blocked and the fluid can’t exit. With open angle, the channel is not obstructed. In the western world, 90 percent of glaucoma is of the open angle type.
Vision loss is caused by progressive damage to the optic nerve. The eye is similar to a video camera. It is connected to the vision center in the brain by a cable that is called the optic nerve. The nerve is a bundle of about 1 to 1.5 million nerve fibers. In glaucoma, for a reason we still do not fully understand, these fibers begin to die off. Without proper treatment, the number of fibers will continue decline and, with that, the patient’s vision.
It used to be thought that the loss of nerve fibers was the result of a high pressure inside the eye. Studies have shown that damage can actually occur at normal or even low pressures. Current thinking is that an elevated pressure is a risk factor for glaucoma but not the disease itself. As it is the only risk factor that can be treated, all current treatment of glaucoma involves lowering the eye pressure. This can be achieved by using topical medication (drops), laser therapy, surgery or a combination of treatments. Successful treatment will lower the pressure to the point that no further nerve fibers and, hence, vision will be lost.
There are three main reasons why people go blind from this disease. First, they are not diagnosed. Recent studies have estimated about 1 million people in the United States with glaucoma are currently undiagnosed. Although many factors are involved here, the two main culprits are lack of symptoms until very late in the disease and failure to routinely have a thorough eye examination.
The second reason is that patients are notoriously non-compliant with their therapy. There have been many papers, articles and even YouTube videos about this. But the bottom line is this—no treatment is effective if it is not used.
Finally, treatment has to be sufficient to slow or stop disease progression. If therapy is inadequate, the benefit of accurate diagnosis and compliance will suffer.
Glaucoma can be diagnosed at any age, but is more common after the age of 40. Vision loss is completely preventable with early diagnosis and proper treatment. This cannot happen without routine eye examinations. A minimum examination would consist of a measurement of eye pressure and a dilated stereoscopic evaluation of the optic nerve. If there is evidence of increased risk, a more detailed investigation would include formal test of the visual field and optic nerve imaging.
Remember—glaucoma is known as the “silent thief of sight” as there are no symptoms until late in the disease. If you are over 40, have a family history of glaucoma or any other risk factors, make sure to have your eyes examined regularly.
Dr. John J. O’Donnell Jr. is an optometrist with Premier Eye Care Group. For more information, visit www.premiereyes.com.
