On March 4, 2016, the United States Food and Drug Administration (FDA) announced that it would allow the marketing of the Triggerfish® Sensor, a “smart” contact lens that may help eye doctors identify the best time of day to measure a patient’s intraocular [i.e., within the eye] pressure, or IOP. Elevated IOP is often associated with the optic nerve damage that is characteristic of glaucoma.
The FDA granted this approval via the de novo premarket review pathway, a regulatory pathway for low- to moderate-risk medical devices that are not substantially equivalent to an already legally-marketed device.
About the Triggerfish “Smart” Contact Lens
The Triggerfish® Sensor (pictured above) is a soft hydrophilic [i.e., composed of plastics called hydrogels that absorb water] contact lens that monitors eye pressure in glaucoma. It was developed by Sensimed AG, a Swiss technology company that designs and develops micro-systems for medical devices.
The Triggerfish® lens is a sensor that monitors changes in the curvature of the cornea, the transparent dome-shaped tissue that forms the front part of the eye. According to Sensimed, these changes in the cornea correspond directly to fluctuations in intraocular pressure, which is characteristic of certain types of glaucoma.
Eye pressure data from the Triggerfish® lens is transmitted wirelessly to a small adhesive antenna placed on the face near the eye. The antenna then transmits the data to a portable recorder worn by the patient. The lens can be worn continuously for one 24-hour period. You can view a diagram of the Triggerfish system at the Sensimed AG website.
When the patient returns to his or her eye doctor, the data is transferred from the recorder to the doctor’s computer via Bluetooth technology for immediate analysis. Data provided by the Triggerfish lens allows the doctor to observe peaks in patients’ eye pressure, which can vary throughout the day. This information can be used to optimize the type, dosage, and timing of glaucoma medications to better control intraocular pressure.
[Editor’s note: More recent research indicates that intraocular pressure (IOP) rises and falls throughout the day and night. It is often lower during waking hours (called diurnal) when doctors typically see patients, and higher at night (called nocturnal) when patients are usually asleep.]
More about Glaucoma
Glaucoma is a group of eye diseases that damage the optic nerve and is one of the leading causes of vision loss and blindness. Open-angle glaucoma is the most common (but not the only) form of glaucoma.
The eye continuously produces a fluid, called the aqueous (or aqueous humor), that must drain from the eye in order to maintain healthy eye pressure. Aqueous humor is a clear, watery fluid that flows continuously into, and out of, the anterior (or front) chamber of the eye, which is the fluid-filled space between the iris and the cornea. It is the aqueous that helps to bring nutrients to the various parts of the eye.
Aqueous fluid drains from the anterior chamber through a filtering meshwork of spongy tissue along the outer edge of the iris (called the trabecular meshwork), where the iris and cornea meet, and into a series of “tubes,” called Schlemm’s canal, that drain the fluid out of the eye. Problems with the flow of aqueous fluid can lead to elevated pressure within the eye.
In primary open-angle glaucoma, the filtering meshwork may become blocked or may drain too slowly. If the aqueous fluid cannot flow out of the eye, or flow out quickly enough, pressure builds inside the eye and can rise to levels that may damage the optic nerve, resulting in vision loss.
Most eye care professionals define the range of normal intraocular pressure (IOP) as between 10 and 21 mm Hg [i.e., millimeters of mercury, which is a pressure measurement]. Most persons with glaucoma have an IOP measurement of greater than 21 mm Hg.
If you have been diagnosed with glaucoma, it is critical to maintain the treatment plan prescribed by your eye doctor. You can read more about glaucoma medication regimens and additional treatments at What Are the Different Treatments for Glaucoma?, What are the Different Types of Glaucoma?, and Patient’s Guide to Living with Glaucoma on the VisionAware website.
Vision Loss from Glaucoma
Glaucoma results in peripheral (or side) vision loss initially, and as this field loss progresses, the effect is like looking through a tube or into a narrow tunnel. This constricted “tunnel vision” effect makes it difficult to walk without bumping into objects that are off to the side, near the head, or at foot level.
A living room viewed through a constricted visual field.
Source: Making Life More Livable. Used with permission.
Glaucoma is an especially dangerous eye condition because most people do not experience any symptoms or early warning signs at the onset. Glaucoma can be treated, but it is not curable. The damage to the optic nerve from glaucoma cannot be reversed.
Clinical Trials and Research Supporting the Triggerfish
There have been two United States-based Triggerfish clinical trials, entitled Sensimed Triggerfish Safety and Tolerability and Efficacy of 24-Hour Intraocular Pressure Fluctuation Recording with the Sensimed Triggerfish Contact Lens Sensor, both conducted at the University of California, San Diego Shiley Eye Institute. Additional clinical trials/studies have been conducted in Belgium, Canada, Denmark, France, Germany, Poland, Israel, India, Spain, and Switzerland.
The purpose of the Triggerfish Safety and Tolerability trial was to evaluate the level of comfort/discomfort in the study eye after wearing the Triggerfish lens for a 24-hour period, in addition to documenting any side effects.
The purpose of the 24-Hour Intraocular Pressure Fluctuation trial was to evaluate the safety and effectiveness of the Triggerfish lens in recording accurate fluctuations in intraocular pressure.
In addition, new research in the journal Ophthalmology, entitled Visual Field Change and 24-Hour IOP-Related Profile with a Contact Lens Sensor in Treated Glaucoma Patients concludes that “Intraocular pressure-related parameters obtained with 24-hour recording with a contact lens sensor (CLS) were associated with the rate of visual field progression in treated glaucomatous eyes. This technology may be useful in detecting eyes at higher risk of glaucoma progression while receiving treatment.”
The FDA Triggerfish Announcement
Excerpted from FDA permits marketing of device that senses optimal time to check patient’s eye pressure, via the FDA Newsroom:
The U.S. Food and Drug Administration today allowed marketing of a one-time use contact lens that may help practitioners identify the best time of day to measure a patient’s intraocular pressure (IOP).
“The Triggerfish gives the clinician 24-hour continuous monitoring of changes in IOP patterns that otherwise could not be obtained,” said William Maisel, M.D., M.P.H., acting director of the Office of Device Evaluation in the FDA’s Center for Devices and Radiological Health. “This information can help determine the most critical time of day for the clinician to measure the patient’s IOP.”
The device does not actually measure IOP, is not intended to be a diagnostic tool, and is not used to correct vision.
Glaucoma is a leading cause of vision loss and affects an estimated 3 million Americans. Many patients have no symptoms until significant vision has been lost, and this loss is irreversible. IOP varies throughout the day and may not be abnormally high when the patient is at an eye care professional’s office having an eye exam. For example, it is common for IOP to increase during sleep when the patient is lying down.
The Triggerfish is indicated for use in adults age 22 and older under the direction and supervision of a health care professional.
Clinical data supporting the marketing authorization of the Triggerfish included several studies of the safety and tolerability of the contact lenses and the effectiveness of the device measurement. The effectiveness of the device was demonstrated by showing an association between the Triggerfish device output and IOP fluctuation.
The most common temporary side effects were pressure marks from the contact lens, ocular hyperemia (red eyes) and punctate keratitis (irritation of the cornea).