Nanogirl Michelle Dickinson: Is your phone blinding you?

Research suggests that in addition to altering our sleep patterns, the blue light from our phone screens could be accelerating blindness. Photo / Getty Images

COMMENT: Many of us know that we shouldn't check our electronic devices in bed because the light emitted from the screen can disrupt our sleep. New research suggests that too much of this screen light at night could also lead to the acceleration of macular degeneration, one of the leading causes of age-related blindness.

Light is made up of waves, with different colours of light having different energies. At one end of the visible spectrum is red light which is made up of low energy waves, at the other end is blue light which has higher energy and penetrates all the way to the retina at the back of the eye.

We get this high energy blue light naturally in the day from the sun, and it helps us to regulate our sleeping patterns.

As our eyes are exposed to sunlight in the morning our bodies release enzymes which reduce melatonin levels helping us to wake up. As the sun goes down, the amount of blue light that we are exposed to naturally reduces, more melatonin is released and we start to feel sleepy.

The screens on our digital devices emit high energy blue light as do energy efficient fluorescent bulbs and LED lights. By staring at our screens after sundown, we can cause disruption to our circadian rhythm by reducing the amount of melatonin released around bedtime causing difficulties in naturally getting to sleep at night.

Research published in the journal Scientific Reports suggests that in addition to altering our sleep patterns, the blue light from our screens could also be accelerating blindness as we age.

Macular degeneration is the leading cause of age-related vision loss affecting about one in seven New Zealanders aged over 50. As an incurable eye disease it results in significant vision loss and is caused by the death of photoreceptor cells in the retina.

Vision is created through photoreceptor cells in the eye which use special molecules called retinal. Retinal - which is a form of vitamin A - changes shape when hit by photons from light, and this shape change initiates a series of chemical reactions which send electrical signals along the optic nerve to be interpreted by the brain.

The researchers found that when they exposed retinal molecules to blue light in the lab it triggered a reaction which generated a chemical that was poisonous to the photoreceptor cells in the eye.

This toxic chemical dissolved the signalling molecule on the membrane of the photoreceptor cell resulting in the cell's death.

Naturally, our bodies use vitamin E as an antioxidant to reduce the amount of retinal damage caused by blue light. However, as we age our levels of vitamin E reduce which also lowers our natural protection.

When the surrounding light levels are low, our pupils are dilated meaning they can take in a lot of light. By checking our devices in bed when the lights are out, we are susceptible to more blue light entering our eyes through our dilated pupils which could potentially cause increased cell damage speeding up macular degeneration and potentially leading to an acceleration of blindness in many.

Although more research is needed, the study opens up big questions around screen time at night as well as exposure in children whose corneas haven't fully developed yet.

Several other factors including diet, exercise and smoking are also known to advance macular degeneration and night-time apps that warm the computer display are also easily installed.

However for the sake of your eyes and your sleep, it might be worth leaving your devices alone at bedtime from now on.