Lucy Q. Shen, MD, is an instructor in ophthalmology at Harvard Medical School and a glaucoma specialist at Massachusetts Eye and Ear Infirmary, both in Boston. She has been awarded a Harvard Medical School Catalyst grant in support of her research.
My eagle-eyed neighbor likes to crow about the fact that, at 60-something, she still doesn’t need glasses for reading or driving. She’s so pleased by this that she hasn’t bothered to visit an eye doctor in many years—an attitude that I consider to be dangerously shortsighted. Reason: Glaucoma, the number-two cause of blindness in the US, often causes no early symptoms…yet unless the condition is detected early, permanent vision loss is likely.
The good news is that a five-minute, in-office laser procedure can successfully treat glaucoma in many cases, I heard from Lucy Shen, MD, a Harvard Medical School instructor and glaucoma specialist at Massachusetts Eye and Ear Infirmary. But of course, to take advantage of that option, you first have to have given your eye doctor a chance to discover the problem! Glaucoma risk increases with age, which is one reason why the American Academy of Ophthalmology recommends getting a baseline comprehensive eye exam at age 40, plus regular follow-up exams.
Glaucoma basics: In most cases, glaucoma develops when an imbalance in the production and drainage of fluid in the eye allows pressure to build up within the eye. The abnormally high intraocular pressure (IOP) damages the optic nerve that carries visual information from the eye to the brain, resulting in progressive and irreversible vision loss.
Though there are various types of glaucoma, by far the most common is open-angle glaucoma (so we’ll focus on that type now and cover other types at a later date). Open-angle glaucoma occurs when the trabecular meshwork, a system of microscopic drainage channels encircling the iris, slowly become clogged with debris and dysfunctional, and thus cannot drain eye fluid effectively. Note: We’re talking about fluid inside of the eye. “Many patients think this is related to tearing—but tearing is because the fluid made on the surface of the eye does not drain well through a channel outside of the eye, on the eyelid,” Dr. Shen explained.
With open-angle glaucoma, optic nerve damage is slow and painless and peripheral (side) vision is affected first. That is why people often don’t notice a problem until a significant portion of their vision is irretrievably lost.
Once the condition is detected, the first line of treatment usually consists of medicated eyedrops that reduce production of eye fluids and/or help increase drainage. Oral medications, such as certain diuretics, also may be used. If those treatments don’t halt the disease—or if the patient develops an allergy to the eyedrops, as happens with about 5% to 10% of patients in her practice Dr. Shen said—the ophthalmologist may recommend a procedure called laser trabeculoplasty to improve the drainage function of the trabecular network and thus reduce IOP.
Sight-saving laser treatment: The procedure generally is done in the ophthalmologist’s office. After administering eye-numbing drops, the doctor positions a special contact lens on the eye to control blinking, reduce small eye movements and facilitate focusing of the laser. Then the laser is aimed at the trabecular meshwork, the internal drainage area of the eye, in a procedure that takes about five minutes. Though it is not painful, some patients report feeling a little sore afterward, Dr. Shen said.
There are two laser options. With argon laser trabeculoplasty (ALT), a high-energy laser typically is applied in evenly spaced spots over the trabecular meshwork, causing shrinkage that creates openings to improve drainage. However, because tiny scars can eventually form, ALT cannot be repeated in the same area even if IOP eventually rises again. Recent advance: The newer selective laser trabeculoplasty (SLT) uses a lower-energy laser to selectively target the trabecular meshwork. It stimulates the cells in the drainage channels to clean up the debris that is compromising drainage. Because scarring is unlikely, SLT can be repeated to keep pressure under control—which is one reason why Dr. Shen uses SLT instead of ALT.
Possible complications after ALT or SLT, though rare, include inflammation, pain, temporary cloudy vision and a potential rise in IOP. To minimize risks: Ask the ophthalmologist you are considering how many patients he or she has treated and the treatment success rate, defined as achieving a 30% reduction in IOP. You want a doctor whose success rate is around 80% or better. Also ask how many of the doctor’s patients have needed to be treated a second time. Ideally, the majority of patients are treated only once—but do understand that it is not uncommon to require additional laser treatment.
Important: Even after successful ALT or SLT, most patients still need medication to keep open-angle glaucoma from progressing. And of course, follow-up eye exams are essential to protect vision.