It's a selfie that might save your sight. An implanted sensor could help people with glaucoma monitor the pressure in their eyes using a smartphone camera.
The second biggest cause of blindness after cataracts, glaucoma occurs when fluid builds up in the eye. This raises the pressure, damaging the optic nerve. Accurate pressure readings are crucial for giving the right treatment, but one-off measurements during check-ups produce variable results and can be misleading.
Yossi Mandel at Bar-Ilan University in Ramat Gan, Israel, and his colleagues have developed a pressure sensor which can be inserted into the eye during surgery to provide easy, regular monitoring from home.
A few millimetres in length, the sensor can be embedded into the synthetic lenses used to replace the natural lenses of people with cataracts. It works like a miniature barometer, and contains a fluid column that rises with eye pressure. The level can be read at any time using a smartphone camera fitted with a special optical adapter. Software then analyses the image and calculates the reading.
"Continuous monitoring is a clear unmet need in glaucoma," says Francesca Cordeiro, a glaucoma researcher at University College London.
Mandel believes self-monitoring will lead to better treatment of glaucoma, and could enable people to skip unnecessary appointments when their eye pressures are on target.
Several eye pressure probes have been developed since the early 1990s. These include a contact lens made by Sensimed, based in Lausanne, Switzerland, that can estimate eye pressure based on how the cornea bends. Sensimed's sensor is the only wearable pressure device that is commercially available, but it is intended for short-term use only. Mandel says his sensor could be installed in a patient's eye for many years.
Implanting the synthetic lens that contains the sensor would require invasive surgery, something only suitable for patients who need new lenses anyway due to cataracts.
"Ultimately, only a small proportion of glaucoma patients could benefit from this sensor," says Cordeiro. Developing a standalone sensor that could be implanted in front of the iris could solve this problem, suggests Mandel.