Glaucoma is a group of eye conditions that damage the optic nerve, which transmits visual information from the eye to the brain. This condition is associated with elevated intraocular pressure (IOP), often resulting from an imbalance between the production and drainage of the eye's fluid, known as aqueous humor. If left untreated, glaucoma can lead to irreversible vision loss and, in severe cases, blindness. It is estimated that over three million Americans are affected by glaucoma, making it a leading cause of blindness in the United States.
One of the challenging aspects of glaucoma management is its asymptomatic nature in the early stages, earning it the moniker "the silent thief of sight." Many individuals may not realize they have glaucoma until significant damage has occurred. Therefore, early detection is crucial for effective management. While there is no cure for glaucoma, timely intervention through various treatments, including medications, laser therapy, and surgery, can often slow down the progression of the disease.
Regular eye exams, especially for individuals over the age of 40 or those with a family history of glaucoma, are essential for early detection. Screening for the condition primarily involves measuring IOP, as increased pressure is a key risk factor. However, while these screenings are essential, they may not be sufficient. In reality, IOP measurements can vary greatly throughout the course of a day, so taking a measurement at a single point in time, as is done in clinical settings, can be very misleading.
A practical method to collect frequent IOP measurements would go a long way towards the goal of early detection of glaucoma. A collaboration between researchers at the University of Northumbria and Bogazici University has led to the development of a new technology that might fill this present gap. They have developed contact lenses with tiny, embedded sensors that can transparently record IOP measurements from the wearer throughout the course of a day.
The team started with a standard soft, disposable contact lens. They then inserted electrically passive, metamaterial-based resonators into each lens. When the sensor is stressed mechanically, as it is when IOP levels change, it results in changes to the geometry of the sensor. To capture a measurement, a wearable antenna and custom circuit transmit low power radio frequency signals, which are then reflected back to the wearable device. On their return, the signals will have been modulated by the sensors in a way that can be translated into an IOP measurement.
This approach offers a number of advantages. First and foremost, it can collect continuous IOP measurements over an extended period of time, revealing the true likelihood that an individual has glaucoma. Moreover, since the sensor is electrically passive, it is very simple and thin, and it requires no batteries or other sources of power. This makes it unobtrusive and greatly enhances the safety of this device, which is quite important considering it is placed directly on the eyes.
A small pilot study was conducted to assess how well the contact lens performs. Six healthy participants were recruited for the trial. After being fitted with the contact lenses, they were asked to drink a large amount of water to intentionally change their IOP. Measurements were then captured from the new sensors, as well as with a tonometer, which is the present gold-standard method of measuring IOP in clinical settings. While the findings are preliminary, the system was found to work as expected, indicating that the new sensor could potentially be used clinically in the future.
At present, the researchers have plans to conduct larger-scale experiments to further validate their device. Looking even further ahead, they hope to use their system to provide early diagnoses of other diseases.