After blindness, the adult brain can learn to see again

More than 40 million people worldwide are blind, and many of them reach this condition after many years of slow and progressive retinal degeneration. The development of sophisticated prostheses or new light-responsive elements, aiming to replace the disrupted retinal function and to feed restored visual signals to the brain, has provided new hope. However, very little is known about whether the brain of blind people retains residual capacity to process restored or artificial visual inputs. A new study published in the open-access journal PLOS Biology by Elisa Castaldi and Maria Concetta Morrone from the University of Pisa, Italy, and colleagues investigates the brain’s capability to process visual information after many years of total blindness, by studying patients affected by Retinitis Pigmentosa, a hereditary illness of the retina that gradually leads to complete blindness.

Fundus of the patient’s eye implanted with Argus II Retinal 98 Prosthesis, taken soon after the surgery Image Credit: Castaldi E, Cicchini GM, Cinelli L, Biagi L, Rizzo S, Morrone MC (2016)

 

The perceptual and brain responses of a group of patients were assessed before and after the implantation of a prosthetic implant that senses visual signals and transmits them to the brain by stimulating axons of retinal ganglion cells. Using functional magnetic resonance imaging, the researchers found that patients learned to recognize unusual visual stimuli, such as flashes of light, and that this ability correlated with increased brain activity. However, this change in brain activity, observed at both the thalamic and cortical level, took extensive training over a long period of time to become established: the more the patient practiced, the more their brain responded to visual stimuli, and the better they perceived the visual stimuli using the implant. In other words, the brain needs to learn to see again.

The results are important as they show that after the implantation of a prosthetic device the brain undergoes plastic changes to re-learn how to make use of the new artificial and probably aberrant visual signals. They demonstrate a residual plasticity of the sensory circuitry of the adult brain after many years of deprivation, which can be exploited in the development of new prosthetic implants.

Article: Visual BOLD Response in Late Blind Subjects with Argus II Retinal Prosthesis, Castaldi E, Cicchini GM, Cinelli L, Biagi L, Rizzo S, Morrone MC, PLOS Biology, doi:10.1371/journal.pbio.1002569,


Eye health: Our top tips for healthy eyes

Eye health

Our top tips for healthy eyes

  • Have regular check-ups

Have your eyes tested every two years even if you think your vision is fine. An eye test can spot some eye conditions and other illnesses not related to sight. Regular check-ups are vital even if you have no symptoms.

  • Find out your family eye health history

Talk to your relatives about your family eye health history. Some eye conditions have genetic links which increase your risk of developing them. Share this information with your optometrist or eye health professional.

  • Take care of your contact lenses

If you wear contact lenses make sure you look after them properly. Thoroughly wash and dry your hands before touching your contact lenses or your eyes. Your lenses and their case should only ever be cleaned with the lens solution recommended by your optometrist. Always follow the instructions given to you by your optometrist or the lens manufacturer.

  • Wear sunglasses

Protect your eyes when it is sunny or when you’re in high glare areas such as near snow or water. The CE or BS EN 1836:2005 marks indicate that sunglasses provide a safe level of protection from the sun’s damaging UVA and UVB rays. Ongoing UV exposure can increase your risk of developing cataracts or macular degeneration.

  • Protect your eyes

Wear safety glasses or protective goggles to protect your eyes from injury if you work with hazardous or airborne materials. This applies to home too if you are doing DIY, gardening or setting off fireworks.

  • Keep fit and healthy

Being fit and well can help your eyes stay healthy. Maintaining a healthy weight and blood pressure may help with eye health. Protect your eyes when playing sports involving flying balls.

  • Eat well

Make sure your diet includes nutrients such as Omega 3 fatty acids, zinc and vitamins C and E. These may help to prevent or delay age-related vision problems such as macular degeneration and cataracts. Recommended foods for general good health include green leafy vegetables, oily fish such as salmon and citrus fruits.

  • Stop smoking

Smoking is harmful to your eyes and can increase the risk of sight loss. Current smokers are 2-4 times more at risk of developing macular degeneration than people who have never smoked.

  • Avoid recreational drugs

There is evidence to suggest that some recreational drugs can cause sight loss – particularly alkyl nitrites, also known as poppers.

 

Facts about sight loss

  • Every 5 seconds someone in the world goes blind
  • Every day 100 people in the UK start to lose their sight
  • Almost 2 million people in the UK are living with significant sight loss. The number is predicted to rise to around 2.3 million by 2020 and almost 4 million by 2050
  • Around 360,000 people in the UK are registered blind or partially sighted
  • An estimated 25,000 children in Britain are blind or partially sighted
  • 86% of people in the UK value their sight above any other sense
  • Sight loss can affect people of any age but the likelihood increases as you get older: One in five people over 70 are living with sight loss
  • Black and Asian people are at greater risk of developing certain conditions which can result in the onset of some of the leading causes of sight loss