Glaucoma is the second leading treatable cause of blindness in the United States. Like other chronic disorders, the eye disease often requires long-term medication.
The most common form, open-angle glaucoma, develops when the clear, watery liquid (called aqueous humor) that circulates through the front part of the eye can’t adequately drain because the structurethough which it flows out becomes partially blocked. As a result, the pressure in the eye (known as intraocular pressure, or IOP) rises, which can damage the optic nerve and lead to blindness.
Lowering IOP can protect the optic nerve and help preserve vision. Prescription eyedrops that reduce IOP are usually the first choice of therapy for newly diagnosed glaucoma patients. These solutions work by improving drainage of aqueous humor from the eye or slowing down fluid production.
Fortunately, the array of treatments to lower IOP is growing. The recent approval of two novel drugs and broader use of some surgical techniques give people with glaucoma more treatment options. In 2017, the FDA approved the first new classes of glaucoma medications since the 1990s.
Latanoprostene bunod eyedrops
The first new drug, latanoprostene bunod (Vyzulta), is a once-daily eyedrop that’s nearly identical to latanoprost (Xalatan, Xelpros, generic), which has been around for more than 20 years. Both drugs contain a prostaglandin-like substance. They belong to the most frequently used class of glaucoma drugs, which work by improving the drainage of aqueous humor.
Unlike latanoprost, however, latanoprostene bunod is a dual-action drug—it also reduces IOP by promoting the release of nitric oxide, a molecule that appears to improve aqueous humor drainage by a different mechanism.
The FDA approved latanoprostene bunod based on the results of two clinical trials. In the trials, the new drug lowered IOP slightly more than latanoprost and timolol (Timoptic, Betimol), a beta blocker commonly used to treat glaucoma.
Latanoprostene bunod carries a risk for eye redness and irritation and an increase in iris pigmentation. The drug also promotes eyelash growth, which may be more noticeable when only one eye is treated.
The FDA also approved netarsudil (Rhopressa), the first in a new class of drugs called rho kinase inhibitors. These once-daily eyedrops appear to lower IOP by reducing aqueous humor production andincreasing fluid drainage. A study published in the February 2018 issue of American Journal of Ophthalmology found that netarsudil lowered IOP as effectively as timolol, but only in patients who started with an IOP of 25 mm Hg (millimeters of mercury) or less. Normal pressure ranges between 12 mm Hg and 20 mm Hg.
In clinical trials, about half of users experienced eye redness. Other side effects include whorl-shaped deposits on the cornea and burst blood vessels under the thin membrane that covers the white of the eye.
Unfortunately, neither new drug is yet covered by Medicare. However, it’s worth checking your Medicare Part D’s formulary—the list of drugs your plan covers—to see whether either drug is added in2019. Both drugs are expensive if you pay out of pocket: One 2.5 ml (milliliters) eyedropper of netarsudil costs upward of $230 for about a 25-day supply, and a 5 ml eyedropper of latanoprostene bunod costsmore than $360 for about a 50-day suppl
Glaucoma surgery: in wider use
While most glaucoma patients use eyedrops, laser therapy, which increases the drainage of fluid in the eye, is a reasonable option for some, suggests the American Academy of Ophthalmology. Such patients include those who may miss or skip drug doses because they have memory problems, have difficulty applying the drops, or can’t tolerate drugs.
IOP can also be reduced using a surgical procedure known as trabeculectomy, though it’s usually only offered when pressure isn’t lowered with drug or laser therapy.In addition, doctors are increasingly recommending a surgical implant early in the course of glaucoma that in the past was mainly reserved for hard-to-treat cases. An aqueous shunt is a tiny flexible tube that a surgeon inserts near the front of the eye. The shunt takes in aqueous humor, which drains out near the back of the eyeball, allowing the fluid to be absorbed by surrounding tissues.
A variety of aqueous shunts are available, though there’s too little comparison data to say which is most effective, according to an analysis published in 2017 by the Cochrane Database of Systematic Reviews. The study authors also concluded that research is not sufficient to assess whether aqueous shunts lower IOP better than trabeculectomy; the review didn’t compare shunts to laser treatments.
This article first appeared in the January 2019 issue of UC Berkeley Health After 50.