Engineers in the US have developed a glowing contact lens technology that they claim could help prevent blindness in millions of people with diabetes.
Developed by a team at the California Institute of Technology (Caltech) the innovative technology, which uses similar technology to luminous wrist-watches designed to emit low levels of light into the wearers eye at night, reducing the oxygen demands of the eye, and limiting the impact of diabetic retinopathy, a condition often associated with diabetes in its more advanced stages.
The loss of vision that accompanies diabetes is the result of the damage the disease causes to tiny blood vessels throughout the body, including those in the eye. That damage results in reduced blood flow to the nerve cells in the retina and their eventual death.
As the disease progresses, the body attempts to counteract the effects of the damaged blood vessels by growing new ones within the retina. In diabetes patients, however, these vessels tend to be badly developed and bleed into the clear fluid inside the eye, obscuring vision and compounding eyesight problems.
Because damage to the retina begins with an insufficient supply of oxygen, it should be possible to stave off further eyesight loss by reducing the retina’s oxygen demands. Until now, that’s been achieved by using a laser to burn away the cells in the peripheral parts of the retina, so the oxygen those cells would have required can be used by the more important vision cells in the centre of the retina. Another treatment requires injecting medication that reduces the growth of new blood vessels directly into the eyeball.
Caltech graduate student Colin Cook, who led the development of the technology, claims that the glowing lenses could offer a non-invasive alternative to existing treatments.
The lenses work by providing the eye’s rod cells, which provide vision in low-light conditions, with a faint amount of light as the user sleeps.
Rod cells consume almost twice as much oxygen in the dark and it’s thought that much of the damage caused to the retina by diabetic retinopathy occurs when they crank up their oxygen demands at night. The light emitted by the Caltech lenses reduces this night-time oxygen demand.
The illumination provided by the lenses comes from tiny vials filled with tritium, a radioactive form of hydrogen gas that emits electrons as it decays. Those electrons are converted into light by a phosphorescent coating.
The vials, which are only the width of a few human hairs, are implanted in the lens in a radial pattern like the rays of a cartoon sun. The vials create a circle that is just big enough to fall outside of the wearer’s view when the pupils are constricted in lighted conditions. In the dark, the pupil expands, and the faint glow from the vials can illuminate the retina.
While light therapy for diabetic retinopathy has been attempted before in the form of lighted sleep masks, patients had difficulty tolerating the masks and ignoring the light shining into their eyes as they slept. Cook said his lenses avoid that problem by placing the light source on the surface of the eye, so when the eye moves, the light source moves with it, and there is no flicker for the wearer to notice.
Early testing of the lenses is showing promising results, with rod cell activity reduced by as much as 90 percent when worn in the dark. Cook said in the next few months, he and his fellow researchers will start testing the lenses to see if their ability to reduce retinal metabolism will translate into the prevention of diabetic retinopathy. Following those tests, they will seek FDA permits to begin clinical trials.
