Diabetic retinopathy is a complication of diabetes and is a leading cause of blindness among working-age adults (20 to 65 years) with diabetes. As described by ophthalmologist Dr. Niall Crosby, diabetic retinopathy “affects the light-sensitive film at the back of the eye, known as the retina”.
There are two main types of diabetic retinopathy:
Non-proliferative diabetic retinopathy
This is the earlier stage of diabetic retinopathy, where blood vessels in the retina are damaged due to diabetes, but abnormal new blood vessels have not yet started to grow (proliferate). It is characterised by little weaknesses in the blood vessels of the retina that sometimes bleed and leak. At this stage, your vision is usually not impacted.
Non-proliferative diabetic retinopathy is often classified into mild, moderate, and severe stages based on the extent of damage.
Proliferative diabetic retinopathy
The next stage of diabetic retinopathy is associated with a high risk of blindness. It happens due to the growth of abnormal new blood vessels to overcome blockages in the retina’s blood vessels. These abnormal new vessels are fragile and very weak, and they tend to rupture and bleed into the eyes, causing blurred vision, which can be very serious. The abnormal blood vessels may also scar and cause retinal detachment.
Sometimes, you may suffer from a slightly related version of diabetic retinopathy known as diabetic maculopathy and this happens when the blood vessels in the macula (the central part of the retina) leaks or becomes blocked. This can occur in the early or later stages alongside diabetic retinopathy and causes blurring of vision.
“The main cause of diabetic retinopathy is, obviously, diabetes,” shares Dr. Niall. “And the more severe the diabetes, the worse it's controlled, and the longer the duration of the diabetes, the more likely the patient is to have diabetic retinopathy.”
Other factors that may contribute to the development of diabetic retinopathy include high blood pressure, kidney disease, and high cholesterol, but you will have to be diabetic first.
According to Singapore’s HealthHub, diabetes affects approximately one in twelve Singaporeans aged 18 to 69, and between those aged between 60 and 69, this figure is higher at one in three. Globally, approximately 35.4% of diabetic patients have diabetic retinopathy, and in Singapore, the prevalence of diabetic retinopathy is higher than other Asian countries, at 33.9%.
Thankfully, diabetic retinopathy is not inevitable for someone with diabetes.
“It's well known that about half of diabetics, after about 20 years, will develop some form of diabetic retinopathy. Now, that may be very mild, or it may be more severe; it also depends on whether you have type one or type two diabetes,” explains Dr. Niall. “For type one diabetes, after about 20 years, 60% of type one diabetics will have some diabetic retinopathy, and the percentage is a bit lower for type two diabetics.”
The better your diabetes is controlled, and if other risk factors such as your blood pressure, cholesterol, and kidney disease are also under control, then your risk of developing diabetic retinopathy is much lower.
The early non-proliferative stages of diabetic retinopathy usually do not exhibit symptoms, and there are no symptoms that anyone would notice unless someone actually looks inside the eye, or takes a photograph, and looks carefully at the retina.
Later on, as the disease progresses, blood vessels in the retina may start to bleed, resulting in blurred vision or little floaters in your visions or dark spots.
Dr. Niall adds, “If there's bleeding, sometimes there may be distortion of the vision; if there's a lot of leakage affecting the central parts [of your retina], those straight lines may appear curved or wavy.”
The main risk factor for diabetic retinopathy is the control of the diabetes itself.
“If you are diabetic, you would be familiar with a blood test that you would have about every three months performed by either your endocrinologist or your GP, known as the HbA1c test,” explains Dr. Niall. “This gives an idea of the average blood sugar control that you have over a period of time, and it's well-established that if your HbA1c level is below seven, then the risk of diabetes is lower, whereas if it’s above seven, the risk is higher, and obviously higher levels than that of HbA1c are associated with higher risks of getting severe diabetic retinopathy changes.”
Other risk factors of diabetic retinopathy include:
To detect diabetic retinopathy, your eye doctor may choose to conduct a comprehensive dilated eye exam. For this exam, eye drops will be placed in your eyes to dilate your pupils to allow your doctors to better view inside your eyes and spot the little telltale signs of diabetic retinopathy.
Dr. Crosby shared that for more severe cases of diabetic retinopathy, more advanced imaging tests, such as three-dimensional scans of the retina, may be taken to look for leakages.
“Sometimes we do dye tests where we inject a dye into the bloodstream that will show us if there're leaking areas or areas that are getting poor blood supply and are vulnerable to damage, and that can help us decide the best treatment for the person with diabetic retinopathy,” explains Dr. Niall.
The treatment for diabetic retinopathy depends on how severe the condition is.
Hence, the earliest stages of diabetic retinopathy usually require no treatment of the eye itself, but ophthalmologists may liaise and work with the patient’s endocrinologist or GP to ensure the patient’s blood sugar, HbA1c, blood pressure, and other risk factors are kept under control through ways such as medication or diet and lifestyle changes.
For more advanced stages of diabetic retinopathy, also known as severe pre-proliferative or proliferative diabetic retinopathy, treatment is necessary.
“It’s been shown to be beneficial to have treatment with either laser to the eye or injections in the eye, which can shrink the abnormal blood vessels around the retina,” says Dr. Niall. “This prevents bleeding and leakage, which can damage the retina and impact vision.”
The best way to prevent diabetic retinopathy is to ensure you regularly attend your check-ups with either your endocrinologist or your GP who manages your diabetes. This is to make sure that you control not only your diabetes but all other associated risk factors.
“One of the most important factors, as we've discussed, is the HbA1c level, and it's important to make sure that's below 7%,” states Dr. Niall. “There was a large study performed several years ago in the UK, known as the UK Prospective Diabetes Study, which established that every 1% drop in the HbA1c level resulted in a 31% reduction in the chance of developing complications of diabetic retinopathy.”
Other factors to manage include your blood pressure and cholesterol, making sure any kidney disease you may have is under control, not smoking, and living a generally healthy lifestyle.
As an ophthalmologist, Dr. Niall has one last thing to add: “One of the most important things you can do to prevent diabetic retinopathy, or at least the more severe types of diabetic retinopathy, is to have your eyes screened at least once a year, either with photography or with an eye doctor, just to make sure you're not developing any early signs of diabetic retinopathy.”
