Diabetes is a condition that causes your blood sugar level to be too high. It’s relatively common: 1 in 15 people in the UK have it.(1) It can cause a range of symptoms, such as weight loss and fatigue, but on top of this, it can also cause problems with your eyes and vision.

Particularly, diabetes has been linked to glaucoma, a condition that initially can cause blurriness in your peripheral vision, but if left unchecked causes permanent sight loss, or ‘tunnel vision’. These two conditions can have a big impact on our lives, so we’ll take a closer look at both — and see how they are connected.

What is diabetes?

There are two main types of diabetes — Type 1 and Type 2 — and both cause you to have too much glucose (sugar) in your blood. You need glucose to give you energy: when you eat and drink, the carbohydrates break down, produce glucose, and cause your pancreas to release a hormone called insulin. If everything is working well, it senses when glucose arrives and releases the right amount of insulin, so you get the right amount of glucose in your cells to fuel your body. For people with diabetes, however, this system doesn’t work.

People with Type 1 diabetes don’t create insulin at all. For those with Type 2, they either don’t make enough insulin or it doesn’t work effectively. For both types of diabetes, though, glucose that can’t get into cells where it’s needed builds up in the bloodstream instead. This can cause symptoms like, feeling thirsty, needing the toilet, and feeling tired. People with undetected and untreated diabetes may also lose weight, skin wounds may heal slowly, and they may also be prone to infections such as thrush. In the long term, without treatment, the high levels of glucose can cause serious problems with the heart, feet, kidneys and eyes.

What is glaucoma?

Glaucoma is a condition where the nerve fibres at the back of the eye are damaged, generally by a build-up of pressure from the fluid inside the eyes. The increased pressure can damage the optic nerve, which ultimately causes vision loss. The most common type of glaucoma is primary open-angle glaucoma, though there are many different types.

It’s difficult to identify when you have glaucoma, as for most people this increase in eye pressure is gradual and painless. Often glaucoma is only detectable through having an eye test, and the main symptom (if any) is a loss or blurriness of sight in your peripheral vision, which if untreated, can lead to tunnel vision. However, because these vision changes are slow, and may only affect one eye, many people either don’t realise their vision is changing, or the other eye compensates for the loss of sight. This is why regular eye tests are so important, even if you feel there is nothing wrong with your vision. There are also other, rarer symptoms which may indicate glaucoma, such as increased eye pain, headache, and tenderness around the eyes.

The link between glaucoma and diabetes

Research confirms a link between glaucoma and diabetes — and though the risk for glaucoma in everyone increases with age, if you do have diabetes, you’re at a higher risk of developing the condition.(2) A study in Australia of more than 3,500 older people found a significant association between diabetes and glaucoma, while another study of almost 5,000 older people in the US found that open-angle glaucoma is more common in people with older-onset diabetes. (3,4)

A separate study of more than 4,000 older people in the Netherlands, which looked for signs of diabetes and glaucoma, found that newly diagnosed diabetes and high levels of blood glucose are linked to glaucoma.5 These studies looked at one type of glaucoma, primary open-angle glaucoma, which is more common if you have Type 2 diabetes. There is also another type of glaucoma, neovascular glaucoma, which is related to the abnormal blood vessel growth in the eye which blocks the natural drainage of the eye. This type can affect people with Type 1 and Type 2 diabetes equally, according to a Danish study.(6)

The best thing you can do is to go for regular eye tests, which is once every two years (or whenever your optician recommends it). When you have an eye test, your optician will assess your level of vision, the health of the optic nerve, eye pressures and will also evaluate your visual field, checking how much you can see in the edge of your vision.

It’s important to have all these tests as glaucoma can develop gradually, and for some people it can even occur when the pressure in the eye is at normal levels. In fact 40% of people in the UK with glaucoma have what is considered to be a normal eye pressure. A full eye examination will help the optician to pick up early signs of glaucoma (and other eye problems) before your vision is affected, and advise you on treatment options if necessary.

If you’ve been having any problems with your eyesight or want to know more about your eye health, you can book an appointment at your local Specsavers.

For more information on the causes of glaucoma, you can find it in our dedicated glaucoma hub.


1. Diabetes UK. (no date). Diabetes: the basics. Diabetes UK. [Online]. Available at: https://www.diabetes.org.uk/diabetes-the-basics [Accessed 08 May 2019].
2. Ou, Y. (2017). Glaucoma and Diabetes. BrightFocus Foundation. [Online]. Available at: https://www.brightfocus.org/glaucoma/article/glaucoma-and-diabetes [Accessed 08 May 2019].
3. Mitchell, P., et al. (1997). Open-angle Glaucoma and Diabetes. Ophthalmology, 104(04). [Online]. Available at: https://www.aaojournal.org/article/S0161-6420(97)30247-4/pdf [Accessed 08 May 2019].
4. Klein, B., et al. (1994). Open-angle Glaucoma and Older-onset Diabetes. Ophthalmology, 101(07). [Online]. Available at: https://www.aaojournal.org/article/S0161-6420(94)31191-2/pdf [Accessed 08 May 2019].
5. Dielemans, I., et al. (1996). Primary Open-angle Glaucoma, Intraocular Pressure, and Diabetes Mellitus in the General Elderly Population. Ophthalmology, 103(08). [Online]. Available at: https://www.aaojournal.org/article/S0161-6420(96)30511-3/pdf [Accessed 08 May 2019].
6. Neilsen, N. V. (1983). The prevalence of glaucoma and ocular hypertension in Type 1 and Type 2 diabetes mellitus. Acta Opthalmologica, 61(04). [Online]. Available at: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1755-3768.1983.tb04357.x [Accessed 08 May 2019].

Kevin Liu
MOptom (Hons) MCOptom Dip Tp(IP) Prof Cert Glau Prof Cert Med Ret

Kevin is the Optometrist Director at Specsavers in Altrincham, Sale and Urmston. His background lies in education with previous roles as a chemistry teacher and Lecturer… Read more