Docs test contact lens that can measure eye pressure over 24 hours

TREATMENT for the eye disorder glaucoma is set to get a high-tech twist. 

Doctors at the Singapore National Eye Centre (SNEC) are studying the use of a 'smart' contact lens that can measure patients' eye pressure round the clock - even as they sleep.  This is a step up from the current practice in which patients usually get just a single reading of their eye pressure, and only when they see their doctor. Doctors thus do not know what the readings at other times are.

Professor Aung Tin, who heads SNEC's glaucoma service, says when readings are taken at five-minute intervals over 24 hours, doctors can manage their patients' conditions better.  'Eye pressure fluctuates all day long, and some people have greater fluctuations than others,' he said.

Glaucoma is a condition in which the optic nerve becomes slowly damaged, causing blindness over time. Several factors, including elevated eye pressure, can damage the optic nerve.  The disease affects about 6 per cent of Singaporeans and accounts for 40 per cent of vision loss here.

The lens, the Triggerfish Sensor, will be tested on 60 patients here, to assess its suitability for Asians.  Made by Swiss company Sensimed, it has been approved for clinical use in Europe and is awaiting approval from the US Food and Drug Administration. It has not been cleared for use here, except for investigative research.

The main component of the device is a disposable contact lens made of soft silicone. Embedded in it are a microchip and a gold circular gauge which picks up the small changes in eye pressure.  Patients using it need to have two external devices - an antenna to receive the readings from the lens, and a recorder to store the data.

The antenna looks like one half of a pair of spectacle frames, except that it adheres to the skin. Readings are transmitted wirelessly to it. The battery-operated, pocket-sized recorder carried by the patient gets the readings wired to it from the antenna.  After 24 hours, the patient has the lens removed and turns in the data.

SNEC paid about $1,000 for a set of these devices. Its eventual price has not been set yet as it has not been launched here commercially.

Dr Baskaran Mani, a lead investigator in the study and a senior research fellow at the Singapore Eye Research Institute, said the lenses can help doctors avoid misdiagnosis.  Data from the US and Europe shows 11 per cent to 16 per cent of patients have their eye pressure over-estimated. Under-estimation of eye pressure occurs in about half of glaucoma patients.  Both situations can lead to wrong diagnoses and errors in managing patients' conditions, said Dr Baskaran.

So far, three patients have tried Triggerfish; two more will do so soon.

Lorry driver Lau Eng Choon, 67, was fitted with the lens last month, then underwent a laser procedure to treat his glaucoma, based on the data gathered.  Two weeks later, he was fitted with the lens a second time. By comparing the 'before' and 'after' readings, his doctor could assess the effectiveness of the laser procedure, said Dr Baskaran.  Mr Lau, who had never worn any kind of lenses before, said he found the Triggerfish lens comfortable.  His only gripe: The antenna scores low on looks. 'If I go out like this, people will stare at me. So I hide at home for the day,' he said with a laugh.