Many people are familiar with the word “glaucoma” and they associate it with the eyes, but a large majority are unaware of the significance of the disease and how it can affect daily life. Glaucoma truly is a disease where the less you know about it, the more it can hurt you. It is one of the leading causes of blindness in the world according to the World Health Organization. In the United States, the most common form of glaucoma is open-angle glaucoma. This is a silent disease that slowly causes loss of peripheral vision and can eventually lead to blindness. It’s called “silent” because symptoms are almost always absent until the disease reaches an advanced stage. Sadly, once vision loss occurs from glaucoma, it’s irreversible.
Risk factors for glaucoma include high eye pressure, increasing age, poorly controlled blood pressure, untreated sleep apnea, and diabetes. People who have parents or siblings with glaucoma are also at higher risk for the disease. Glaucoma occurs in people of all races, however those of African-American and Hispanic descent are at greater risk. In Caucasians, glaucoma is present in an average of 2 out of every 100 individuals. This risk, however, increases by as much as 10 fold in individuals over the age of 75.
Glaucoma is best diagnosed by an eye doctor during a dilated eye examination. By using drops to dilate the pupils, this allows the doctor a window to see the vital structures in the back of the eye, including the optic nerve and retina. Glaucoma technically is an optic neuropathy–meaning a disease of the optic nerve, the nerve that transports the visual “message” from the eye to the brain. As damage occurs from glaucoma, the optic nerve usually changes appearance and this change can be detected by the examiner, especially when a doctor can follow a patient over time with regular eye examinations. If a patient has risk factors for the disease and the doctor has suspicion based on examination findings, additional testing will often be performed to help evaluate a patient’s true risk and confirm the presence or absence of damage. Common tests performed include visual field testing that meticulously maps a patient’s peripheral vision and optic nerve imaging to measure the optic nerve itself or retinal layers around the optic nerve. Corneal pachymetry is also very helpful–this measures the thickness of the cornea, the clear dome at the front of the eye—since studies have shown that patients with thin corneas are at greater risk of glaucoma. In addition to the above, an exciting advance in the field of glaucoma detection is pattern VEP/ERG that’s now available at Eye Doctors of Lancaster. This testing was only previously done at large academic centers and was very costly and time-consuming, but with technology and statistical modeling breakthroughs, it’s now available in the office and can help detect early damage from glaucoma as much as 8 years prior to other testing methods.
Treatment for glaucoma presently consists of one primary goal—lowering eye pressure (intraocular pressure or IOP for short). IOP is determined by a balance between the volume of fluid made inside the eye vs the volume of fluid that leaves the eye over a given time. This fluid, called aqueous humor, is independent of the tear film that lubricates and protects the surface of the eye. Aqueous is made in the ciliary body which is located behind the iris, the colored part of the eye. It circulates through the pupil into the front segment of the eye called the anterior chamber, then drains out of the eye and into the veins of the eye socket (orbit) through an anatomic landmark called the angle of the eye.
Lowering IOP can be done by one of 3 methods: medication, laser and surgery. Because of increased risks, traditional glaucoma surgery is reserved for patients in whom glaucoma is worsening despite maximal medical treatment. Therefore, this discussion will focus on treatment using medications and/or laser. Although oral medications are available to treat glaucoma, bothersome side effects usually limit their use, so most glaucoma medications today are topical in the form of eye drops. These drops either reduce aqueous production, increase aqueous drainage or both. There are several different families of medicated eye drops, but just like medications for blood pressure control, each type of eye drop needs to be applied at least once daily and sometimes up to 3 times daily to keep the eye pressure controlled.
Instead of or in addition to medication, laser treatments can be done to lower IOP. Although different types of lasers are used for various eye diseases, the type primarily used for open angle glaucoma is called laser trabeculoplasty. Traditionally, this was performed by an argon laser (ALT) that would burn tiny openings in the angle of the eye to allow aqueous to drain into the veins of the orbit more easily. Over the last several years, however, an exciting advance has been made in laser technology called Selective Laser Trabeculoplasty (SLT). The laser energy (fluence) required for the SLT procedure is 4000 times less per laser pulse and lasts only 3 nanoseconds. This tiny amount of energy is absorbed by pigmented cells in the angle and causes no surrounding thermal damage. Instead, microscopic changes in the cells stimulate the body to remove debris from the angle. An analogy Dr. Donnelly likes to use with his patients when describing this procedure is that SLT sends a message to the body to clean out the drain and lower IOP “just like removing a clump of hair in a bathtub drain allows water to exit the tub more quickly”.
The laser effect usually reaches maximum IOP reduction after 8-12 weeks. One of the great things about SLT aside from its safety is that any IOP reduction that occurs persists for many months and even several years without the need for a patient to remember to use medicated eye drops every day. Once the IOP begins to rise months to years later, SLT can be repeated with good success. Eye Doctors of Lancaster is proud to have invested in this technology for the benefit of our glaucoma patients. SLT is performed in the office after numbing drops are applied, it is painless, and the procedure takes only about 10 minutes to complete. If you have glaucoma and wish to see if this procedure may be for you or if you would like a thorough medical eye exam, please call to schedule an appointment with Dr. Steven Donnelly or Dr. Theodore Jones at Eye Doctors of Lancaster.
Cataracts and Glaucoma
It is not uncommon for patients to develop both cataracts and glaucoma, especially later in life. In addition to the use of medications and SLT to lower intraocular pressure as discussed above, patients can now consider treatment with an iStent at the time of cataract surgery. Unlike traditional glaucoma surgery, the natural wall of the eye is not violated (except for the microscopic cataract surgery incision), so the long term risks of infection and hypotony (meaning the eye pressure dropping too low) is no higher than cataract surgery alone. Click here to learn more about the iStent.