Diabetes mellitus is one of the major health problems affecting the developed regions. It affects the integrity of blood vessels and cause damages in multiple organs. But actually one of the organs that can be severely impaired by diabetes is the eye. There is even a term called diabetic eye disease to describe a group of ocular pathologies that are caused by diabetes and all diabetic eye diseases can lead to severe vision loss or even blindness.
These diseases include cataract, glaucoma, diabetic macular oedema and diabetic retinopathy, while diabetic retinopathy is the most common cause of hampered vision as well as being a leading cause of blindness among working-age adults worldwide. What is the definition of diabetic retinopathy? What are its signs and symptoms? What are the possible treatments of diabetic retinopathy and how can we prevent from having the disease? Now let’s take a better look into diabetic retinopathy.
In diabetic patients, their blood sugar level is higher than normal level. The elevated blood sugar level will damage the capillary blood vessels, which are rich in the retina. The compromised blood vessels will leak fluid and blood, or being blocked that cannot transport oxygen and nutrients to the retinal cells. If leakage happens close to the macula, the macula will swell, namely macular oedema and the vision will be distorted. In the late stage, abnormal blood vessels grow in the retina and these malformed vessels and prone to bleed. The scar tissues formed after bleeding can contract and pull the retina out of its place – this is the blind-causing retinal detachment. The abnormal vessels can also grow at the iris and cause glaucoma which can also cause blindness.
The majority of diabetic patients in developed regions are type II diabetes. In general, the prevalence of diabetic retinopathy in diabetic patients of all ages are around 35%. The chance of having diabetic retinopathy correlates with the diabetes duration. According to the literature, more than 20% patients will have diabetic retinopathy after having type II diabetes for more than 10 years. Meanwhile, the probability increases to 40% after being diabetic for 14 years and reaches to 60% when patients have been type II diabetic for more than 16 years. Other risk factors of diabetic retinopathy include elevated blood sugar level, blood pressure and blood cholesterol level.
It is both a blessing and a curse that early diabetic retinopathy is generally asymptomatic. As patients themselves are unaware of their retinopathy, it can lead to disease progression and patients may experience floaters, blurry vision and vision distortion. In late stage, sudden severe vision loss can take place and it can be permanent. Other signs of diabetic retinopathy include blood and fluid leakage, conformation changes of retinal blood vessels, retinal nerve fibre infarction, macular oedema, growth of abnormal retinal vessels and retinal scarring.
Below are pictures demonstrating some visual symptoms experienced by moderate and late stage diabetic retinopathy:
Visual symptom for moderate diabetic retinopathy.
Image retrieved from
Visual symptom for late stage diabetic retinopathy.
Image retrieved from
Comparison of the same scene viewed by a normal person (left) and by a patient with late stage diabetic retinopathy.
Images retrieved from https://nei.nih.gov/health/diabetic/retinopathy
The progression rate of diabetic retinopathy depends on its current stage and any proper disease management. The late stage of the disease is defined by the growth of abnormal retinal vessels which can cause sudden massive bleeding and can lead to blindness. For mild diabetic retinopathy, 5% of them will progress into late stage in 1 year without proper follow up. But for patients having moderate retinopathy without treatment, 27% of them will progress into late stage within 1 year. For severe diabetic retinopathy, 50% of them will progress into late stage in a year.
To delay the onset as well as control the progression of diabetic retinopathy, the best way is to control the blood sugar level and blood pressure. Patients should keep their HbA1c level, which is one of the parameter showing blood sugar level, in the range of 6-7% to control diabetic retinopathy. Reducing HbA1c level by 1% lowers retinopathy risk by around 30%. Concurrent hypertension together with diabetes increases diabetic retinopathy risk by 10%.
Besides controlling diabetes and blood pressure, treatments can also be done to reduce the severity of signs and symptoms, based on different stages of the disease. For mild diabetic retinopathy, the vision usually remains unaffected and no additional ocular treatment is necessary. For moderate cases that vision is blurred and distorted by macular oedema, laser surgery may be used to seal off the leaking blood vessel and improves the vision. For late stage which abnormal vessels start to grow, medicines that inhibit the growth of abnormal vessels, named anti-VEGF, can be injected inside the eyeball and improve the vision by 1-2 lines on average. But the treatment may need to repeat from monthly to every few months. Some cases may also need to apply laser to burn over the whole retina except sparing the central part, sacrificing the peripheral vision and cut down the oxygen need of the retina to preserve the central vision.
For general diabetic patients and patients having mild diabetic retinopathy, they should receive a comprehensive eye examination, which means including pupil dilation, at optometrists or eye doctors at least every year. For moderate diabetic retinopathy patients, they should review their conditions every 6 months. For severe cases, they have to attend comprehensive eye examinations every 2-3 months to promptly manage any changes.
Same as diabetes, diabetic retinopathy cannot be cured completely. However, the disease is manageable and preventable. More than 90% of blindness cases from diabetic retinopathy can be avoided by early diagnosis and treatment. Besides attending follow ups at your general physician, diabetic patients should also remember to make regular appointments at your optometrist for comprehensive eye examination.
By Jeff Tang, Registered (Part I) Optometrist
Eyecare information by Swisscoat Vision Centre
Address : 23/F Whole Floor, One Midtown, 11 Hoi Shing Rd, Tsuen Wan, N.T., HK
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