Diabetes affects 380 million people worldwide and is a leading cause of kidney failure, amputations, heart failure, stroke, and most pertinent, blindness. Defined by the inability of the body to produce or process insulin correctly, resulting in higher than normal blood sugar1, diabetes has three classifications:
- Type 1: The pancreas does not produce insulin.
- Type 2: The body doesn’t process insulin correctly.
- Gestational: A pregnant woman’s body does not produce insulin or use the insulin it needs correctly. It can occur in women who have never had diabetes and typically goes away after the baby is born.
If you have any type of diabetes, you may be at risk of developing diabetic eye disease.
What is Diabetic Eye Disease?
Diabetic eye disease starts with the blood vessels. Because the blood vessels in our eyes are so delicate, they are often the first to be weakened by the inconsistent blood sugar levels caused by diabetes. Fluctuations in blood glucose levels (controlled by insulin) can potentially damage important parts of your eye, including the retina, lens, vitreous gel and optic nerve.
In some cases, diabetic eye disease can result in permanent vision loss. In 2010, approximately 7.7 million adults with diabetes were diagnosed with diabetic retinopathy, the most common cause of vision loss in people with diabetes3. While this is a scary statistic, there are ways to prevent and treat diabetic eye disease, and early detection can reduce the risk of blindness by 95%2.… so it’s important to learn about what it is and how to prevent/treat/ identify it.
Parts of the eye affected by diabetes:
- Retina – Tissue lining the back of the eye, which is responsible for converting light into impulses. These impulses are sent through the optic nerve to the brain where they are interpreted as images.
- Macula – A small area in the center of the retina responsible for detailed vision (reading, for instance).
- Lens – Located behind the iris, it helps to focus light or an image on the retina.
- Vitreous Gel – Gel-like substance that fills the interior of the eye and helps maintain a round shape.
- Optic Nerve – The largest sensory nerve in the eye, it connects the eye to the brain and sends messages between the retina, brain, and eye muscles.
Diabetic Retinopathy (DR)
Diabetic retinopathy affects the blood vessels of the retina. Diabetics normally do not experience symptoms of DR. Over time, however, weakened blood vessels can cause microaneurysms causing swelling in the eye. When sugar levels are not kept under control, these microaneurysms can progress to macular edema (see below) and macular ischemia (when the blood supply to the macula is cut off), before symptoms finally become noticeable1.
When blood vessels are cut off from oxygen, the retina attempts to grow new blood vessels (neovascularization). However, these new blood vessels do not actually supply proper blood flow to the retina and the accompanying scar tissue can cause the retina to wrinkle or detach. At this stage, bleeding in the vitreous, glaucoma (see below), and even severe vision loss or blindness is possible1.
The longer you have diabetes, the more likely you are to develop diabetic retinopathy. Though it is rare in the beginning stages of the disease, almost all type 1 and most type 2 diabetics will develop some degree of retinopathy within 15-20 years5.
Diabetic Macular Edema (DME)
DME, which commonly accompanies diabetic retinopathy, is when the macula swells due to fluid leaking from the weakened blood vessels in the retina. As diabetic retinopathy progresses, DME becomes more likely, but it can occur at any stage of the disease. DME can result in blurred vision or floating spots and leads to blindness in approximately half of all people with DR2.
Diabetics have nearly double the risk as non-diabetics1 of getting glaucoma, a disease that damages the optic nerve in the eye. When new blood vessels form in the iris, often as a result of DR, there is an increase in eye pressure and neovascular glaucoma presents itself. There have also been studies into the connection between diabetes and primary open-angle glaucoma, the most common form of glaucoma; however, more research is needed6.
Cataracts are caused by high levels of glucose, increasing the production and accumulation of sorbitol in the lens. The lens eventually swells and ultimately leads to the formation of cataracts resulting in cloudy, blurry, or distorted vision7. Usually associated with age, adults with diabetes are 2-5 times more likely to develop cataracts. They also may develop the condition at a younger age and experience a faster progression2.
Symptoms & Risk Factors
If you have diabetes, any change in eyesight is a good reason to make an appointment with your doctor. Eye exams are often the only way to detect diabetic eye disease early1.
Potential symptoms include:
- Floating spots
- Blurred vision
- Dark or empty spots in your field of vision
- Change in color appearance
- Difficulty seeing at night
- Trouble with peripheral vision
- Periodic changes in vision quality
- Vision loss
Across the board, the duration of diabetes is the strongest predictor for the progression of diabetic eye disease. Patients experiencing less than 10 years of diabetes presented fewer cases of DR than patients who have been diabetic for 20 years or more, according to a 2012 study. Additionally, type 1 diabetics were more likely to have DR than type 2, regardless of the duration of diabetes8.
Hormonal changes like puberty and pregnancy can also add to the risk of developing DR. Additional years of prepubertal diabetes increase the risk due to more exposure, and diabetic onset during puberty possibly increases the risk of developing severe retinopathy in patients with type 1 diabetes. Pregnant women with type 1 diabetes are almost three times more likely to show signs of DR than those with type 2, however, it is often fleeting and regresses postpartum4.
Cataracts are typically associated with older age in non-diabetics. However, the body’s inability to produce or process insulin seems to be a stronger risk factor for cataracts than age alone, as it is three times more prevalent in diabetics under 65 when compared to non-diabetics of the same age. Cataract surgery, which is the preferred treatment, can put patients at risk for an increase in DR progression and if retinopathy is present before surgery, it can increase the likelihood of macular edema7.
There are, however, risk factors that you can control. Chronic hyperglycemia, as well as short-term spikes in blood sugar, can have a huge impact on whether you will develop one of these diseases. Patients with high blood sugar are almost three times more likely to have DR compared to diabetics with better blood sugar control8. Though its impact is less than hyperglycemia, high blood pressure increases the chances for eye problems by damaging blood vessels4. Higher cholesterol is also being studied as a possible risk factor for moderate vision loss from DR9.
How to Prevent and Treat Diabetic Eye Disease
The best way to prevent diabetic eye disease is to detect and treat it early. While it can take years for your eyes to progress through the disease, it often does not have recognizable symptoms until vision is impaired. Diabetics must be proactive to detect it by getting a comprehensive dilated eye exam at least once a year5.
A healthy diet, exercise and prescribed medication is key for both diabetes and eye health. By controlling your blood sugar, you can actually slow the development and progression of DR and even protect against the advancement of the disease5. If this isn’t enough to convince you of a healthy diet, then maybe this will: young patients may actually see a reversal of cataracts through controlling blood sugar.
Your doctor may also suggest surgery or medications. As with any treatment, it is important to discuss the right path with your doctor.
In conclusion, as the prevalence of diabetes rises, so too will the prevalence of diabetic eye disease. Diabetic retinopathy is already the most common cause of vision loss among all adults and in 2010 ranked as the fifth most common cause of preventable blindness7. However, severe vision loss is preventable at any stage of diabetes by taking a proactive approach. Intense blood sugar control, taking care of your overall health and making regular visits to your ophthalmologist can all help reduce your risk.
- Boyd, K. “What is Diabetic Retinopathy.” American Association of Ophthalmology. 2013 aao.org/eye-health/diseases/what-is-diabetic-retinopathy
- “Facts About Diabetic Eye Disease.” National Eye Institute. September 2015. https://nei.nih.gov/health/diabetic/retinopathy
- Diabetic Retinopathy Statistics and Data. National Eye Institute. 2010. https://nei.nih.gov/eyedata/diabetic
- Lee, R., Wong, T. and Sabanayagam, C. Epidemiology of diabetic retinopathy, diabetic macular edema and related vision loss. Eye and Vision. 2015 https://eandv.biomedcentral.com/articles/10.1186/s40662-015-0026-2
- Fong, D., Aiello, L., Gardner, T., King, G., Blankenship, G., Cavallerano, J., Ferris, F., and Klein, R. “Retinopathy in Diabetes.” Diabetes Care 2004 http://care.diabetesjournals.org/content/27/suppl_1/s84
- Jeganathan, V., Wang, J., and Wong, T. “Ocular Associations of Diabetes Other Than Diabetic Retinopathy.” American Diabetes Association. 2008. http://care.diabetesjournals.org/content/31/9/1905
- Pollreisz, A. and Schmidt-Erfurth, U. “Diabetic Cataract – Pathogenesis, Epidemiology and Treatment.” Journal of Ophthalmology. 2010 https://www.hindawi.com/journals/joph/2010/608751/
- Yau, J., Rogers, S., Kawasaki, R., Lamoureaux, E., Kowalski, J., Bek, T., Chen, S., Dekker, J., Fletcher, A., Grauslund, J. et al. “Global Prevalence and Major Risk Factors of Diabetic Retinopathy.” Diabetes Care. 2012. http://care.diabetesjournals.org/content/35/3/556
- Mohammad-Ali Javadi, MD and Siamak Zarei-Ghanavati, MD. “Cataracts in Diabetic Patients: A Review Article.” Journal of Ophthalmic & Vision Research. 2008. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3589218/