When you get your eyes checked, you get to read rows of tiny numbers and make a bunch of “Better A, or better B?” choices as the technician or doctor tests selected pairs of lenses to get your subjective feedback. Chances are good that you also rest your chin in a hard plastic cup and braced yourself for a brief puff of air on each eye. That air puff is from a tonomoter and its purpose is to measure the pressure in your eye, aka your “intraocular pressure (IOP)”. A high IOP can be a sign of impending glaucoma. You don’t want to mess with glaucoma, even if Rachel on “Friends” couldn’t sit still for the eye puff test, because glaucoma is the second leading cause of blindness (after cataracts), according to the World Health Organization. One issue with the eye puff test, however, is that IOP isn’t static; it can rise and fall during the day.
Swedish company SENSIMED’s Triggerfish has been developed to provide non-invasive measurements of IOP for a 24 hour period, including sleeping. This data allows medical professionals to see a full day’s variation of pressure in your eye. Triggerfish has three components. The first piece is a contact lens with an embedded micro-sensor that measures changes in the circumference of your eye; it gets bigger as internal pressure increases. The lens does not have a battery but the wirelessly communicates the circumference data to an adhesive patch-like antenna that is worn around the eye socket. The antenna is connected by thin cable to a recorder held in a pouch suspended a necklace worn around your neck or attached to your belt. After the 24 hour period, the recorder goes back to the doctor’s office and the data is transmitted via Bluetooth for study. Triggerfish is not currently approved for use in the United States although it is approved in Canada, several countries each in Central and South America, Asia, and the near east, as well as most of Europe.
Glaucoma is known as the “silent thief of vision” because the disease develops so slowly people often don’t recognize the gradual diminished vision that usually occurs. Tests at Columbia University with Triggerfish have recently been published in Ophthalmology*, the journal of the American Academy of Ophthalmology which showed a correlation between frequency and spikes in intraocular pressure during a 24 hour period and developing glaucoma and underscore the need for more than just a single puff in the eye for effective glaucoma detection.