How does diabetes affect the eyes?
Diabetes is a metabolic disorder that can impact far more than just the sugar levels in the blood. In this article, consultant ophthalmologist Mr Raj Mukherjee explains how vision can be at risk due to diabetes.
Diabetic eye diseases are complications that arise from unmanaged diabetes and can lead to a complete loss of vision.
What causes diabetic eye disease?
Diabetes is a disease where the body is unable to regulate the amount of glucose (sugar) in the blood, which is normally controlled by insulin, a hormone that is created in the pancreas and helps process sugar into energy for consumption. The two commonest types of diabetes are when there is either an autoimmune response (type 1), an accrued insulin resistance, or insufficient insulin production (both type 2).
Too much glucose in the blood will damage the blood vessels, including the tiny capillaries in the eye by causing narrowing and hardening. This makes it more difficult for adequate blood flow, and thus oxygen, to reach organs, muscles, and other corporeal structures, eventually causing them to shut down.
What are the types of diabetic eye disease?
Underneath the umbrella of diabetic eye diseases, there are:
- Diabetic retinopathy: occurs when blood leaks into the retina, which can happen due to breakage in the blood vessels, or due to new blood vessel growth which can occur when old blood vessels are obstructed. This is one of the most prominent causes of blindness in adults.
- Macular oedema: the macula, which is located at the centre of the retina, can become deformed by leaking fluid or blood, causing blurred and distorted vision.
- Glaucoma: a form of glaucoma particular to diabetes is neovascular glaucoma that occurs when there is new blood vessel growth over the iris, resulting in pressure and leading to glaucoma.
- Cataracts: lenses can become cloudier sooner and faster with diabetes.
How is diabetic eye disease treated?
Treatment of diabetic eye disease will focus on suppressing the growth of new blood vessels or stopping the leaking of blood.
To stop the new growth of blood vessels, laser treatment called photocoagulation to create controlled scar tissue that prevents the growth of new blood vessels.
To stop bleeding in the eyes, injections of anti-vascular endothelial growth factor (anti-VEGF) – such as ranibizumab, aflibercept, or faricimab – into the eye can prevent leakage by blocking the production of the VEGF protein that facilitates the growth of new blood vessels. Injections are to be done four to 16 times weekly until the vision stabilises.
Some patients can also be treated with a small implant loaded with steroid medication (dexamethasone), called an intravitreal implant, that can be placed inside the eye to reduce swelling. Once the medication is used up, the implant will eventually dissolve.
If all other treatments fail and there is a lot of blood collated in the eye or scar tissue, then surgery on the eye can be performed to extract some of the ‘jelly’ of the eye through a small incision, called vitrectomy. This can help prevent retinal detachment.