Written by Fariah Rahman General Member
My mother and many members of her family have diabetes. Millions of people in the world have diabetes and you may have friends or family members who are affected as well. Diabetes and high blood sugar levels can have an impact on many organs in the body, including the eyes. That’s why my mother has to get her eyes checked regularly with the optometrist due to her being diabetic.
Diabetic Keratopathy
Many disorders affecting different parts of the eye can occur in patients with diabetes. The cornea is a transparent, outer structure located at the front of the eyes and covers the iris and pupil (Government of Alberta, 2023). It protects your eyes from debris and germs and also plays a role in directing light rays into your eye and focusing them onto the retina to provide vision. The cornea has many nerves and the outermost layer is known as the epithelium (Cleveland Clinic, 2024). Diabetes can have significant negative effects on the cornea, known as diabetic keratopathy (Lutty, 2013). Since the epithelium is the first layer of the eye, it can be damaged easily due to outside forces and needs to be repaired frequently. Diabetes can lead to impaired wound healing and regeneration of the corneal epithelium (Lutty, 2013; Shih et al., 2017). The cornea has the highest concentration of nerve endings of any tissue in the human body. The corneal nerves are involved in essential functions such as blinking, sensation, and tear production (Shaheen et al., 2014). These nerves can experience a reduction in density and other abnormalities in diabetic patients (Shih et al., 2017). Since the corneal epithelium is not functioning optimally, this puts the diabetic patient’s eyes at risk of infections. This can lead to the breakdown of the epithelium, known as corneal erosions (Vieira-Potter et al., 2016; Feldman-Billard & Dupas, 2021). This can also lead to corneal edema which is when fluid accumulates in the cornea leading to swelling. Corneal edema can affect how light passes through the cornea and may cause vision problems (Cleveland Clinic, 2023).
Cataracts
Patients with diabetes are also at a greater risk of developing cataracts, which also affects the lens, leading to its clouding and structural changes. There is a higher risk of cataracts, if they've had the condition for a long time and often experience high blood sugar. Symptoms might be mild at first, but once the cataract affects the eye's center, it can worsen quickly. Common cataract symptoms include impaired vision, halos around lights, heightened sensitivity to light, trouble seeing at night, and colors appearing less vivid. Controlling blood sugar levels and wearing sunglasses that protect your eyes from UV rays can help reduce the risk of cataracts (American Diabetes Association, n.d.).
Dry Eye Syndrome
Diabetic patients also experience dry eye syndrome (DES) which is the most common condition affecting the eye surface (Feldman-Billard & Dupas, 2021). DES occurs in patients with type 1 or type 2 diabetes. High blood sugar can damage the nerves in your eye and cause inflammation leading to DES. It causes discomfort, problems with vision, and affects tear production. Chronic, untreated DES can lead to permanent eye damage. Controlling one’s blood sugar levels can help reduce the risk of DES (Feldman-Billard & Dupas, 2021; Srakocic & Wood, 2022).
Diabetic Retinopathy & Diabetic Macular Edema
Diabetic retinopathy (DR) can also occur in patients with type 1 or type 2 diabetes. The retina is a layer of tissue at the back of the eye that plays a crucial role in vision by sending signals to the brain. When blood sugar levels are elevated, as in diabetes, it can harm the blood vessels within the retina, leading to visual impairment and DR. It can lead to vision problems and blindness; however, this is preventable. DR first starts out as nonproliferative DR where the blood vessels in the retina are affected and swelling, blockages, and leakages occur (Wint et al., 2022). High blood sugar levels in the retina can kill nerve cells and pericytes (Lutty, 2013). Pericytes are cells that are essential for creating blood vessels and regulating blood flow (Attwell et al., 2015). When pericytes die, the capillaries they support turn into empty tubes made of the protein collagen. These tubes cannot carry blood, so the nearby retina does not get enough oxygen. This lack of oxygen causes the body to produce molecules that make blood vessels leakier (Lutty, 2013). As this becomes more severe, areas of the retina become deprived of blood supply and damaged. This leads to proliferative DR, which is when new, abnormal blood vessels start developing within the eye. When blood leaks into the eye, it can partially or completely obstruct your vision (Wint et al., 2022). Diabetic macular edema (DME) is a complication of DR. The macula is at the center of the retina and is needed for central vision. It allows you to discern colors, intricate details, and distant objects. The macula relays visual data to the brain, where it is processed into images. In DME, the macula starts swelling, causing abnormal vision. This happens because fluid from leaking blood vessels accumulates in the retina, which can no longer absorb it. It is crucial that diabetic patients keep their blood sugar levels under control and get their eyes checked regularly, to ensure any problems are caught early on (Pietrangelo & Raju, 2023).
Actions to Take
It is important that diabetic patients take care of their health to help prevent developing different eye conditions. This includes getting eye exams, especially when vision changes occur as well as during pregnancy as that is when DR can worsen. Those who smoke should seek support to quit. One should also ensure that their blood cholesterol, blood pressure, and blood sugar levels are in check as well as maintain regular exercise and a healthy diet (Diabetes Canada, n.d.).
References
Attwell, D., Mishra, A., Hall, C. N., O’Farrell, F. M., & Dalkara, T. (2015). What is a pericyte? Journal of Cerebral Blood Flow & Metabolism, 36(2), 451–455. https://doi.org/10.1177/0271678x15610340
Corneal edema: Causes, symptoms & treatment. Cleveland Clinic. (2023, August 18). https://my.clevelandclinic.org/health/diseases/25203-corneal-edema
Corneas: Why you should appreciate your eye’s windshield. Cleveland Clinic. (2024, September 1). https://my.clevelandclinic.org/health/body/21562-cornea
Curious about cataracts?. Cataracts and Diabetes | ADA. (n.d.). https://diabetes.org/health-wellness/eye-health/curious-about-cataracts#:~:text=What%20Causes%20Cataracts,accelerate%20the%20development%20of%20cataracts.
Eye damage & diabetes. Diabetes Canada. (n.d.). https://www.diabetes.ca/managing-my-diabetes/preventing-complications/eye-damage#:~:text=To%20prevent%20retinopathy%20or%20prevent,by%20managing%20blood%20sugars%20well.
Feldman-Billard, S., & Dupas, B. (2021). Eye disorders other than diabetic retinopathy in patients with diabetes. Diabetes & Metabolism, 47(6), 101279. https://doi.org/10.1016/j.diabet.2021.101279
Healthwise Staff. (2023, September 27). Cornea, Lens, and Iris. MyHealth Alberta, Government of Alberta. https://myhealth.alberta.ca/Health/Pages/conditions.aspx?hwid=tp10754&lang=en-ca#:~:text=The%20cornea%20is%20the%20outer,%2C%20providing%20sharp%2C%20clear%20vision.
Lutty, G. A. (2013). Effects of diabetes on the eye. Investigative Opthalmology & Visual Science, 54(14). https://doi.org/10.1167/iovs.13-12979
Pietrangelo, A., & Raju, L. (2023, November 14). Diabetic retinopathy vs. diabetic macular edema: What to know. Healthline. https://www.healthline.com/health/diabetes/diabetic-retinopathy-vs-diabetic-macular-edema
Shaheen, B. S., Bakir, M., & Jain, S. (2014). Corneal nerves in health and disease. Survey of Ophthalmology, 59(3), 263–285. https://doi.org/10.1016/j.survophthal.2013.09.002
Shih, K. C., Lam, K. S.-L., & Tong, L. (2017). A systematic review on the impact of diabetes mellitus on the ocular surface. Nutrition & Diabetes, 7(3). https://doi.org/10.1038/nutd.2017.4