Is sugar harming your eyes?

By Dr. Dineshani Hettiarachchi Sirisena

Most often, we are blindsided to the effects of blood sugar on our eyes. Especially if you’re a diabetic, uncontrolled sugar levels can lead to poor vision or even blindness over time. We spoke to Dr. Madhuwanthi Dissanayake, consultant eye surgeon and University of Colombo Faculty of Medicine senior lecturer, on care and prevention of diabetic eye disease.

Diabetes can affect your vision in many ways. This includes diabetic retinopathy, cataract, glaucoma, refractive errors, and retinal vein occlusions.

These are a group of eye conditions that has the potential to cause blindness in those with poorly controlled diabetes. Among them, “diabetic retinopathy” is the most common cause of vision loss and the leading cause of vision impairment and blindness in working-age adults. It is estimated that 21-36% of those with diabetes have retinopathy and 6-13% of them have vision-threatening retinopathy, which as the name suggests is a very serious condition. Dr. Dissanayake also mentioned that these individuals more prone to unstable refractive errors; hence, if you’re getting new glasses, it’s best your sugar levels are in check.

Symptoms of diabetic retinopathy

. Initially asymptomatic
. Blurring of vision
. Floaters
. Sudden loss of vision

Floaters may look to you like black or grey specks, strings, or cobwebs that drift about when you move your eyes and appear to dart away when you try to look at them directly. Dr. Dissanayake went on to say that because diabetic retinopathy often goes unnoticed until vision loss occurs, people with diabetes should get a comprehensive dilated eye exam at the time of first diagnosis of diabetes followed by annual check-ups. But they should be done more frequently if retinopathy is detected at any point.

How does the damage occur in diabetic retinopathy?

Persistently high blood sugar can damage the tiny blood vessels in the retina (the light sensitive layer of the eye). As a result, blood can seep out of these capillaries and cause a bleed, thus distorting vision. In its most advanced stage, new abnormal blood vessels proliferate on the surface of the retina. These new vessels are very fragile and rupture easily to cause massive bleeding inside the eye, which can lead to scarring.

Eventually, the scar formed can contract, causing retinal detachment (pulling away of the retina from underlying tissue, like wallpaper peeling away from a wall) and leading to blindness.

The part of your retina that you need for reading, driving, and seeing faces is called the “macula”. High sugar levels can lead to swelling in the macula, which is called diabetic macular edema. Over time, this disease can destroy sharp vision in this part of the eye, leading to partial vision loss or blindness.

Stages of diabetic retinopathy

. Non-proliferative diabetic retinopathy (NPDR) – main feature is seepage of red cells, lipids, and proteins from retinal vessels
. Proliferative diabetic retinopathy (PDR) – with growth of new fragile blood vessels
Reduce your risk of developing diabetic retinopathy, or stop it worsening, by keeping your blood sugar levels, blood pressure, and cholesterol levels under control.

Treatment options

. Control diabetes
. Laser
. Intravitreal injection of anti-VEGF
. Vitrectomy

Control of diabetes is the most important step and is usually sufficient for non-proliferative diabetic retinopathy (NPDR) where there is no new blood vessel formation. However, for the proliferative stage, a combination of laser and intravitreal anti-VEGF injections has the best outcome. Dr. Dissanayake mentioned that patients often require multiple doses of anti-VEGF injections. Hence, she further emphasised the importance of taking preventive measures to halt disease progression.

What aggravates diabetic retinopathy?

. Uncontrolled blood sugar
. High blood pressure
. Pregnancy
. Renal diseases
. Increased cholesterol levels
. Smoking

When you come for a screening test, the ophthalmologist will have to dilate your eyes (make the pupil larger) in order to look at the retina. Hence, you should be prepared for it and avoid activities such as driving and reading soon after the test.

Facilities available locally

. The state sector provides all these treatments free of charge
. Diabetic eye clinics for regular screening
. Vision 2020 initiative

As a part of the Global Vision 2020 initiative for the elimination of avoidable blindness, the Ministry of Health and the College of Ophthalmologists of Sri Lanka are working together to eliminate avoidable blindness. Dr. Dissanayake is an active member in the Vision 2020 programme sub group which addresses diabetic eye diseases. They have several activities in this regard.

The take home message is to get blood sugar, pressure, and cholesterol levels under control and to check your eyes annually to prevent these unwanted complications to see and experience life with healthy eyes.