Researchers are calling for volunteers to help develop a test for colour blindness

Our colour vision comes from the colour sensitive cells in the back of our eye called cones. There are three types of cones sensitive to long- (red), middle- (green) and short-wavelength (blue) light. These cones respond to light in the world around us, and by adding and subtracting all the signals that they produce we get our wide spectrum of colour vision. If we are missing one of these cones or if one of them is not working properly then we are unable to see the same range of colours that a person with all three can see, resulting in a colour vision deficiency.

It is these deficiencies that Vision Science experts in Bradford are hoping to be able to more accurately understand and diagnose with the help of volunteers in their new study.

Colour vision deficiencies (often referred to as colour blindness) are a common condition. Red and green colour deficiencies are the most common type with blue/yellow or no colour vision at all (achromatopsia) less common. Colour vision problems can affect many aspects of everyday life from picking out clothes, to being unable to tell the difference between two sets of sports teams, problems with warning lights in the car or making sense of the tube map, the list goes on.

While there are many ways to test colour vision, all of them require the person to subjectively express what they see on a card or palette or computer. There is no objective test of colour vision available. Researchers are looking at developing a new test which compares results of a computer colour test with the electrical activity recorded from the groups of cones, enabling them to determine what kind of patterns match different kind of colour vision deficiencies.

PhD Student, John Maguire said: “We hope that through this study we will be able to create a test that takes a measure of the response of the different cone cells to test for colour vision problems rather than getting the patient to report what colours or patterns they can see. Such an application would be beneficial in testing a paediatric population and individuals who struggle to communicate.”

The study will also produce an increase in understanding of the pathways used within the eye for colour processing.

The team, led by Professor Declan McKeefry, are looking to recruit a group of participants diagnosed with a colour vision deficiency and also unaffected members of the family, e.g a parent or sibling. They will be performing one of the most up to date computer colour vision tests, which will provide them with a detailed report on the type of colour vision deficiency.

The researchers will place electrodes around the eye and on the head of the participant, and then stimulate the individual groups of cone cells in the eye by flashing very precise sets of coloured lights. The signal recorded from the electrodes, the electroretinogram (or ERG for short) will provide them with information about how those cells are functioning in the eye and also how the signal is being transferred to parts of the brain.

John explains: “We've been exploring ways to isolate the ERG responses from different cell populations in the retina. We not only want to study the responses from the cones as a whole, but we also want to be able to stimulate and examine the responses from individual cone types, red, green and blue separately.

“One of the outcomes of our recent work has been the discovery that red and green cones respond in very different ways to a flash of light. We think this reflects their contribution to colour vision processing and in so doing provides us with an objective functional test of the integrity of the red-green colour vision.”

The project will allow the researchers to further explore the basic characteristics of the cone-isolated ERG and how it can be used in the assessment of normal and abnormal colour vision.

The study will last approximately 90 minutes and anyone wishing to be part of the study or find our more information can contact [email protected]