Singapore study finds longtime Type 2 diabetes patients at risk of having colour vision impaired
By Alfred Chua
Researchers here have found a link between Type 2 diabetes and colour vision deficiency, and they would recommend that this impairment be tested in future as part of the screening for diabetic patients.
The study by SingHealth Polyclinics and Singapore Polytechnic — the largest of its kind involving 849 patients from various ethnic groups aged 21 to 80 — found that one in five patients with Type 2 diabetes have impaired colour vision. This makes it more difficult for them to distinguish similar colour shades.
The research, done from 2013 to 2015, also revealed that the risk of developing impaired colour vision — which has no known cure — increases with age, and with the number of years a patient has diabetes.
Principal investigator Tan Ngiap Chuan from SingHealth Polyclinics told reporters on Tuesday (Jan 16) that while much research has been done on diabetes and its effect on retinal vision — such as causing blindness — “very little is known” about its effect on colour vision.
While impaired colour vision may commonly be known as “colour blindness”, Dr Tan explained that colour blindness as a medical condition is a more extreme type of colour vision deficiency, and it also usually refers to the type of deficiency which has been present since birth.
Colour blindness affects 8 per cent of men and 0.5 per cent of women worldwide. There is no data available on the proportion of the Singapore population who are colour-blind.
The impairment of colour vision can have potential implications in daily life, Dr Tan added. For example, some patients would have difficulty distinguishing cooked food from raw food, or ripe from unripe food.
Furthermore, if the person has a job as a pilot, engineer or architect, where colour differentiation is important for work, his or her performance will also be affected.
Given the significant proportion of Type 2 diabetes patients that could be affected by this deficiency here, the five-person research team is mooting the idea to have colour screening tests as part of diabetes patients’ check-ups.
The 2010 National Health Survey reported that an estimated 11.3 per cent of Singapore residents aged 18 to 69 had diabetes, and the figure is expected to go up to 15 per cent by 2050.
Those who are diabetic have to go for eye screenings yearly, where doctors look out for bleeding or abnormal blood vessels in the eyes resulting from poor diabetes control, and other signs that could lead to blindness, Dr Tan said.
However, tests for colour vision are not easily available and can be costly, he added, pointing to the potential for the team to develop self-test kits and to explore “the feasibility and cost-effectiveness of such a measure”.
To test for colour vision deficiency, participants from Pasir Ris Polyclinic who took part in the study had to have had Type 2 diabetes for at least two years. They had to rearrange a series of 15 coloured caps in a gradient.
Singapore Polytechnic lecturer Sumasri Kallakuri, who was part of the research team, said that the data then helped researchers to classify the severity of the colour deficiency, if any.
The most common type of impairment among participants was tritanomaly, or blue-yellow colour deficiency, which means they had trouble telling blue from green, and yellow from violet.
Other types of impaired colour vision found were deuteranomoly (red-green deficiency) and protanomaly (red-yellow-green deficiency).
While ethnicity, education level and gender did not statistically affect one’s chances of getting impaired colour vision, the researchers found that age played a significant role: Older patients had a higher risk of getting it.
From the study, the average age of those found to have impaired colour vision was around 59 years old.
The team also concluded that participants who had diabetes for at least six years were more likely to develop impaired colour vision.
Commenting on the study’s significance, Dr Tan said that it would hopefully “send a message…about the importance of diabetes prevention…(that it is) good to keep healthy always”.