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Light Treatment for Diabetic Retinopathy
Light therapy for Diabetic Retinopathy can be found in the form of a Sleep Mask which is part of a monitored ophthalmic treatment for Diabetic Retinopathy.

The Sleep Mask is designed to be worn at night, to deliver a precise dose of light therapy during a patient’s normal hours of sleep. It comes in two parts – a plastic “Pod” part, which is inserted into a soft cushioned Fabric Mask. The Pod contains the light sources which, when worn, emit light into the eyes through closed eyelids. Nothing is inserted into the eyes – the treatment is non-invasive. The mask is programmed to administer the correct dose of light each night as part of a continuing therapy.

The colour of the light has been specifically chosen as the most effective for the treatment of Diabetic Retinopathy. The light may initially appear bright when the mask is first worn, but the eyes adjust within a few minutes as the brain learns to ignore the light, by what is known as the Troxler effect. The light from the mask stops the retina from dark adapting, which is thought to affect Diabetic Retinopathy.

How does it work?
In the human eye an image is projected through the lens to the retina at the back of the eye. There are two sorts of cells in the retina that detect the light (the image) and send a signal to the brain. These cells are called rods and cones. The cones work well during the day when there is a lot of light, but at night time the rods, which are more sensitive to low light levels, take over and dark adapt.

As the rods dark adapt they require more oxygen. In a healthy eye there is just enough oxygen to cope with demand, but in a diabetic person’s eye where circulation is compromised, the retina becomes starved of oxygen, a condition known as hypoxia. The body responds by producing a chemical known as VEGF (Vascular Endothelial Growth Factor) that results in the growth of new blood vessels in the eye to supply extra oxygen. These new vessels are weak and leak fluid, which makes the retina thicker. The build-up of fluid is termed Oedema and further reduces the amount of oxygen available, creating a vicious cycle. If the new blood vessels reach the macula (central part of the eye) and there is a build-up of fluid, then a patient’s eyesight, particularly their central vision, is affected. This is known as Macular Oedema.

The Eye Mask light therapy combats this cycle by illuminating the eye overnight through closed eyelids. The colour of the light is specially chosen to be absorbed primarily by the rods without affecting the cones (which would keep people awake), and the brightness is tuned to ensure that the rods do not dark adapt. As the rods do not dark adapt, their oxygen requirements remain at low daytime levels. The effect of this is to slow or stop the production of VEGF, avoid the formation of weak new blood vessels, avoid fluid leakage and oedema and allow the retina to repair itself to the best of its ability.

The device will only operate between the times stated on the product packaging, usually 20:00 until 10:00. This allows the user to wear the mask for a continuous period of up to 8 hours per night within the specified 14 hour operational window. The use of the mask is detected by sensors and recorded onto a chip, all contained within the Pod.

The eye mask is intended as a disposable, single patient use device. At the end of the allocated period, the mask is returned for analysis and a replacement mask is provided.

The collected data simply allows the clinician to compare how regularly the mask has been worn, with changes in vision.