If you suffer from type 2 diabetes, you may be at risk of developing colour blindness.

Although only a small percentage of people worldwide are born with colour blindness (colour vision impairment), a local study has found a link between this eye condition and type 2 diabetes.

Researchers found that age and the duration of diabetes are factors associated with colour blindness — a condition where patients cannot see the correct colour of things, and their life and work are affected by it.

The study by SingHealth Polyclinics and Singapore Polytechnic revealed that colour blindness affects 22.3 percent of people with type 2 diabetes. Those who have had the illness for six years or more have a higher incidence of colour blindness. The risk increases with each year that patients suffer from the condition.

As the incidence of diabetes is expected to rise in the future, so may the number of people with colour blindness, said Dr Tan Ngiap Chuan, Director, Research, SingHealth Polyclinics, who led the research with Ms Samasri Kallakuri, Lecturer, Singapore Polytechnic.

“Diabetes makes people more prone to eye diseases. It can damage the retina and cause blood vessels to bleed, which is the main cause of blindness in Singapore. But little has been done to understand how it contributes to colour blindness,” said Dr Tan, who is also Academic Vice Chair (Research), SingHealth Duke-NUS Family Medicine Academic Clinical Programme.

It was also found that people with poorer vision are more prone to this eye problem. “Interestingly, ethnicity, gender and employment were not significant factors associated with colour blindness. There was also no association with hypertension, dyslipidemia, coronary, cerebrovascular and renal diseases,” he said.

Studying the Link

About 850 people aged 21 to 80, from different ethnic groups, who had diabetes for at least two years, took part in the study at Pasir Ris Polyclinic from 2013 to 2015.

Researchers collected data on the duration of type 2 diabetes and its complications and treatment, blood pressure, weight, body mass index and demographic and medical profiles. Participants also underwent tests for oral glucose tolerance, glycated haemoglobin and fasting lipid profiles.

The next thing for researchers is to explore if a simple colour screening test can be incorporated into the primary health screening process, particularly of diabetes patients, because early detection is key to managing it.

Patients are currently screened with a Farnsworth D-15 instrument where they have to arrange 15 coloured discs onto numbered caps, in a graduated sequence of closely matching hues, to form a circular diagram. An abnormally arranged diagram would indicate which type of colour blindness they have.

Dr Tan said that ultimately, the take-home message is to live a healthy lifestyle and try and prevent diabetes as far as possible.

“If you already have diabetes, then you have to manage it properly to prevent the onset of colour blindness,” he added.

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