What Is Glaucoma
Glaucoma is one of the leading causes of blindness throughout the world affecting millions of people. Glaucoma is typically a painless disease that results in damage to the optic nerve. The optic nerve is the pathway that carries the images that we see to the brain. If left untreated, the disease can destroy the optic nerve leading to permanent loss of vision. The optic nerve can’t regenerate once it is lost, so early detection and treatment of glaucoma is paramount.
Glaucoma may affect anyone, however there are certain “risk factors”. These include people with advancing age, African-American heritage, a family history of glaucoma, diabetes, near-sightedness, far-sightedness, long term steroid treatment, pigment dispersion and a history of injury of trauma to the eye. Patients with a thin cornea are also at risk for glaucoma. A pachymetry (ultrasound measurement of the corneal thickness) is frequently done in a glaucoma screening.
Types of Glaucoma
There are several types of glaucoma, but the 2 major ones are “open-angle” and “closed-angle”. Open-angle glaucoma is the most common type, occurring in about 3 million Americans. This type of glaucoma occurs slowly over time, and affected individuals often do not know they have in until they begin to experience visual problems. Inside the eye, fluid is continually produced to give our eye its nutrients, and there is a drainage angle called the trabecular meshwork. As the meshwork gets less efficient, the intraocular pressure (IOP) gradually builds and the increase in eye pressure damages the optic nerve permanently.
Many patients ask what is an ideal pressure. Unfortunately, each individuals' pressure tolerance is unique. In fact, a percent of glaucoma patients have a condition known as “normal tension glaucoma” where the nerve suffers loss despite pressures under 21mm Hg. This type of glaucoma is still treated by reducing pressure to even lower levels of pressure to try to arrest further damage. A single pressure reading and visit is not sufficient to detect glaucoma. The rate of change in the optic nerve only is determined with time and visual field and nerve testing periodically.
Closed-angle glaucoma is less common. This differs from the open-angle type in that it can cause symptoms (pain & visual loss) suddenly. An “attack” of closed-angle glaucoma is a medical emergency and needs to be treated immediately with laser. The type that you are at risk for can be determined in the office with a quick test known as gonioscopy. People of Asian decent and those with hyperopia (farsightness) have an increased risk of narrow angle glaucoma.
Diagnosis of glaucoma is confirmed with several in-office tests. First, the intraocular pressure is measured by a tonometer. During the test, the eye is numbed with anesthetic drops. Next the drainage angle is inspected by a mirrored device called a gonioscopy to determine the trabecular meshwork’s health and degree that it is open. Next dilation is performed, and a careful inspection of the optic nerve is performed. A normal nerve has more than 1 million healthy nerve fibers. As glaucoma develops, there is a loss of nerve fibers and the optic nerve develops more cupping. A photo of the optic nerve is often taken to document the health of the nerve and more easily track changes with time. A visual field test is used to track and monitor the brightness of lights in your peripheral vision. This test is repeated at least yearly to detect peripheral vision changes that occur with advancing glaucoma to aid in determining treatment. Finally, an HRT (Heidelberg Retinal Tomograph) may be performed to measure the volume and area of your optic nerve to compare you to other healthy patients, and track any loss of your nerve over time.
Glaucoma can be treated successfully in many ways. Treatment typically involves eye drops, laser and/or surgery. If you have glaucoma, it is highly important to take your drops every day. Never stop the drops without consulting your doctor first. Certain drugs prescribed by your medical doctor may influence your glaucoma, so bring an accurate list of your medicine for each visit. Some patients are treated with laser trabeculoplasty either with the argon laser (ALT) or selective laser (SLT). Other patients with more advanced or rapidly progressive glaucoma with need a trabeculectomy, where a filtration bleb is surgically created and managed to give aqueous a new pathway to drain to lower IOP.
The goal of treatment is to prevent loss of vision or loss of the field of vision. Damage that has already occurred because of glaucoma cannot be reversed, but further damage can be prevented. Since most people with glaucoma experience no noticeable symptoms, an eye examination for glaucoma that includes specialized testing is the MOST important tool in preventing vision loss from the disease.
The key to controlling glaucoma is catching it early. The best way to prevent vision loss from glaucoma is to know your risk factors and to have eye examinations at appropriate intervals. Dr. Walker, one of the few glaucoma fellowship-trained specialists in Bucks County, and Dr. Sucheski will be more than happy to answer any of you questions regarding your risks for glaucoma and if treatment is indicated.