Editor’s note: January is National Glaucoma Awareness Month, and VisionAware is bringing you critical information about management of this serious eye condition.
Glaucoma is a diverse group of eye diseases that leads to a characteristic form of damage to the optic nerve. Elevated eye pressure is the primary known risk factor for glaucoma nerve damage and is caused by a buildup of fluid known as the aqueous humor. In a healthy eye, this fluid provides nourishment to cells before flowing out into the bloodstream through a drainage system made up of the primary outflow pathway, the trabecular meshwork, and the smaller uveoscleral pathway. When the drainage system is blocked, intraocular pressure increases can put a person at risk of developing glaucoma. Therefore, the mainstay of glaucoma therapy has been the use of eye drops that either decrease the production of the aqueous humor or increase the outflow in order to stabilize the intraocular pressure (IOP).
After 20 Years, Major Medical Breakthroughs
Today’s commonly used glaucoma medications were approved in the 1970s. Other medications with different chemical compounds followed, but until now, there had been no major medical breakthrough since 1998. With the FDA approval of two new medications, Aerie Pharmaceutical’s Rhopressa and Bausch + Lomb/Nicox’s Vyzulta, 2018 promises to usher in a new era for glaucoma treatments.
Dr. Louis Cantor, Professor of Ophthalmology and Jay C. Lucile, L. Kahn Chair of Glaucoma Research and Education at Indiana University School of Medicine are not surprised at the excitement generated in the field as these medications emerge from the pipeline onto the market. Dr. Cantor served as the Principal Investigator in the clinical trials for both drugs at the university’s Glick Eye Institute, which has long demonstrated a commitment to bringing novel therapeutic advances to glaucoma. "The medications we have had until now have been great tools. But with Rhopressa and Vyzulta, we have some better options for patients whose needs were not being met."
Rhopressa
Rhopressa (netarsudil ophthalmic solution 0.02%) reduces IOP specifically by improving outflow of the trabecular meshwork, a pathway from which most of the aqueous humor drains. Medications commonly used today target only the secondary drainage system, the uveoscleral pathway, or reduce aqueous production. Rhopressa is a safe and effective alternative to medications that targeted the trabecular meshwork but were mostly abandoned 20 years ago due to adverse side effects.
In addition, Rhopressa also has a unique advantage in treating normal tension glaucoma, which results in damage to the optic nerve despite only slight elevations in intraocular pressure. Patients with this type of glaucoma have a much lower baseline for IOP, but current medications are limited in their ability to lower the eye pressure further and to protect the health of the optic nerve.
The added benefit of this eye-drop is that it is used only once daily instead of requiring multiple applications in a 24-hour period. Dr. Cantor recognizes that eye drops are not always easy to use and trying to manage a routine involving a multitude of drops with different colored caps can be daunting. "Hopefully the simplified, once-a-day treatment will encourage patients to stick to the prescribed regimen."
Vyzulta
Vyzulta (latanoprostene bunod 0.024%) works to lower intraocular pressure by opening the uveoscleral pathway much like other prostaglandin analogs such as Xalatan, Lumigan, Travatan-Z, and Zioptan. But an innovative component of the drug is the presence of nitric oxide, which dilates blood vessels. Stabilizing eye pressure is critical to preserving vision, yet recent research has shown that an insufficient blood supply to the optic nerve may also contribute to the onset of glaucoma.
Dr. Cantor explains, "Many glaucoma patients have auto-regulatory deficits meaning their systems are unable to regulate blood flow to the optic nerve. Vyzulta works to lower pressure while simultaneously dilating blood vessels to improve blood flow. There is even speculation that future clinical studies will prove that the medication has a neuroprotective effect—making the optic nerve more resistant to damage."
A Renaissance in Glaucoma Research
Vyzulta and Rhopressa have arrived on a wave of new insights into the causes of glaucoma and other therapies. While scientists are confident that the medications are effective, they are still exploring the minutiae of how they work. "The development of these new medications combined with the explosion in the surgical arena with micro-invasive glaucoma surgery seem to signal a renaissance in the field of glaucoma treatments," Dr. Cantor said. Researchers, doctors and, of course, their patients have cause to celebrate.