The Connection Between Glaucoma and Diabetes

Glaucoma is a multifactorial condition characterised by an increase in intraocular pressure. It is also a leading cause of permanent blindness, which significantly affects the quality of life. One of the most prominent risk factors is Diabetes mellitus, a disease which is rising at an alarming rate.

Meta-analyses have revealed a 1.4 fold increase in glaucoma risk in people with diabetes. Here, we will further explore the relationship between diabetes and glaucoma. But, before that, let’s understand glaucoma.

Glaucoma: An Introduction

Glaucoma is a progressive disease of the eyes that occurs due to high-pressure build-up. As a result, this leads to the gradual death of retinal ganglion cells. Unfortunately, this disease is a leading cause of irreversible blindness worldwide and has become a significant health issue. In addition, glaucoma adversely affects the quality of life in affected individuals.

A study evaluated the various problems of a glaucoma patient, the most frequent issues encountered were reading, walking on stairs, and recognising people. 

According to data, glaucoma falls into two broad categories: open-angle glaucoma and angle-closure glaucoma. More than 80% of the cases are open-angle types. However, angle-closure glaucoma is responsible for a more severe type of vision loss.

In open-angle glaucoma, the pressure in the eye builds very slowly, while it is very sudden in the case of closed-angle or angle-closure glaucoma. Therefore, angle-closure glaucoma is a medical emergency which requires immediate treatment.

Pathogenesis of Glaucoma.

Over one million optic fibres travel through the optic nerve, which transmits the visual signals from the receptors within the retina to the areas of the brain. As a result, our eyes produce a clear fluid known as the aqueous humour, which gets drained via certain meshworks. However, in glaucoma, there is decreased drainage of aqueous humour. As a result, it increases the level of intraocular pressure. This increased pressure can cause mechanical stress and strain on the eye’s structures. This stress and strain cause compression, deformation and remodelling of the optic nerves. It affects visual acuity and may lead to permanent blindness in a few cases. 

Glaucoma is a disease that is generally symptomless for long periods. The symptoms only appear after significant damage has occurred. Hence, many people with glaucoma are usually unaware of their state and only find out after it is too late.

Does Diabetes Cause Glaucoma?

Several common mechanisms contribute to the possible link between glaucoma and diabetic retinopathy. 

A study reveals that diabetes doubles the chances of having glaucoma. It can cause swelling in the macula, called diabetic macular oedema. The part of your retina that helps you read, drive, and see faces is called the macula. Over a while, the disease can destroy the sharp vision in this part of the eye. That leads to blindness or partial vision loss. Usually, macular oedema develops in people who already have other signs of diabetic retinopathy.

Diabetic Retinopathy: What is it?

Diabetic retinopathy is an eye condition that can lead to vision loss and blindness in people who have diabetes. It is one of the most common causes of blindness in adults between 30 and 65. Studies show that it accounts for 5% of blindness globally and 15–17% of blindness in developed countries. The prevalence of Diabetic retinopathy increases with the duration of diabetes. Almost all individuals with type 1 diabetes and most of those with type 2 diabetes have some degree of Diabetic retinopathy after 20 years.

Cause of Diabetic Retinopathy

Hyperglycemia increases the blood flow to the retina. It disrupts intracellular metabolism and leads to impaired vascular autoregulation. The capillaries eventually become unable to supply blood to the retinal cells, called capillary hypoperfusion, which may ultimately lead to capillary closure. Unfortunately, this leads to the death of retinal cells. The death of retinal cells causes stimulation of growth factors. These growth factors cause the formation of abnormal blood vessels, which bleed and further worsen the condition. 

Features of Diabetic Retinopathy

Diabetic retinopathy is a progressive condition that falls into two non-proliferative and proliferative stages. The nonproliferative stage causes micro-aneurysms and retinal haemorrhages. As it progresses, we can see venous bleeding and vascular abnormalities. This stage then advances to the proliferative phase, where the retina is severely damaged. There is retinal fibrosis and scarring and the formation of new blood vessels that often bleed. 

Diabetic Eye Disease: Who is at Risk?

Anyone with prolonged diabetes can develop diabetic eye disease. However, your risk is greater if you have any of the two additional conditions, which are:

• Unregulated High blood glucose levels
• Untreated High blood pressure

Smoking and high blood cholesterol may also raise your risk for diabetic eye disease.

Some groups are affected more than others. For example, African Americans, American Indians and Alaska Natives, Hispanics/Latinos, Pacific Islanders, and older adults are at greater risk of such diseases.

If you become pregnant and have diabetes, you can develop eye problems very quickly during your pregnancy. Furthermore, if you already have some diabetic retinopathy, it can worsen during pregnancy. In addition, changes that help your body support a growing baby may stress your eye’s blood vessels. Therefore, your health care team will suggest regular eye exams during pregnancy to catch and treat problems early and protect your vision. However, one research claims that diabetes that occurs only during pregnancy, called gestational diabetes, does not usually cause eye problems. 

Prevention of Diabetic Retinopathy

It is essential to maintain your blood sugar levels to avoid the risk of diabetic retinopathy and associated glaucoma. In addition, certain diet and lifestyle modifications can go a long way in avoiding these conditions.

Diet Modifications 

1. Fruits and Vegetables 

Studies have shown that the risk for diabetic retinopathy declines with increased intake of fruits and vegetables.

The mechanisms by which fruits and vegetables exert preventive effects on diabetic retinopathy are unclear. Still, data suggests it may be due to the involvement of vitamin C, carotene, retinol equivalent, and dietary fibre. In addition, a high-fruit-vegetable intervention can increase carotene and vitamin C levels in plasma.

Another possibility is that the preventive effects of fruits happen through glycemic control. Fruits are low-glycemic-index foods rich in dietary fibre, which can slow glucose response after ingestion. It may also be due to dietary fibre that might reduce damage to the retina caused by glucose.

Another study suggested that adults with diabetes consuming more flavonoid-rich fruits and vegetables had lower degrees of inflammation, better glycemic control, and reduced odds of diabetic retinopathy.

2. Polyunsaturated Fatty Acids

There are two main types of fats: Saturated and Unsaturated fatty acids. If a fat molecule has no double bonds, it is saturated fat. If it has double bonds, it is known as unsaturated fat. They are further divided into polyunsaturated and monounsaturated fatty acids. If a fat molecule has only one double bond, it’s called monounsaturated fat. But if it has more than one bond, it’s called polyunsaturated fat.

Polyunsaturated fats and monounsaturated fats are healthy fats, while saturated fats are bad fats. Research has found that increased Polyunsaturated Fatty Acids intake was associated with a reduced likelihood of the presence and severity of Diabetic retinopathy. In contrast, increasing Saturated Fatty Acid intake was associated with an increased probability of the presence and severity of Diabetic retinopathy. 

The two major classes of polyunsaturated fats are omega-3 and omega-6 fatty acids. These are essential fatty acids meaning our bodies cannot produce them, and we can only procure them from the diet. FOA/WHO recommends 250 mg/day or 30-40g/week.

Let’s see some foods rich in polyunsaturated fats.

Mackerel

Mackerel is a small fish which is popular in smoked forms. According to USDA, 100 grams of mackerel contains 3.35 grams of PUFA. In addition, it is rich in protein content and has good levels of vitamin E.

Salmon

Salmon is a versatile and nutritionally rich food. According to USDA, 100 grams of salmon contains around 2.5 grams of PUFA. In addition, it is also rich in various micronutrients like Vitamin B6, Folate, vitamin B12 and vitamin A.

Chia Seeds

Chia seeds are very dense in Polyunsaturated fatty acids. According to the USDA, 100 grams of Chia seeds contain around 23.7 grams of PUFA. They are also rich in essential amino acids required for building protein, hormones and enzymes.

Walnuts

Walnuts are nutritious foods rich in micronutrients like iron, manganese, potassium and vitamin E. According to USDA, 100 grams of Walnuts contain 47.2 grams of PUFA. Also, they are high in antioxidants which offer protection against damage.

3. Mediterranean Diet

Studies have shown that greater adherence to the Mediterranean diet can significantly reduce the risk of diabetic retinopathy. In addition, it reduces the risk of overall mortality, cardiovascular diseases, coronary heart disease, myocardial infarction, overall cancer incidence, neurodegenerative diseases and type 2 diabetes.

The Mediterranean diet contains traditional ingredients, flavours, cooking methods, and eating habits of the people of the countries along the Mediterranean Sea. In the beginning, it drew on the cuisines of Greece, Turkey, Italy, and Spain. In decades since, it has also incorporated other Mediterranean cuisines, such as those in the Levant and North Africa. The Mediterranean Diet is a predominantly plant-based diet based around vegetables, whole grains, and beans. It advocates less consumption of red meat.

The general principles of the Mediterranean diet are as follows:

• Consume these every day: Leafy greens, vegetables, fruits, whole grains, beans, nuts, and legumes.
• Consume these foods weekly: Lean proteins from fish, some poultry, and eggs.
• Try to avoid these foods: Red meats and sweets.
• Use Extra Virgin olive oil regularly: According to a study, the Mediterranean diet with olive oil leads to an over 40% reduced risk of retinopathy.
• Avoid processed foods.

Lifestyle Modifications 

1. Physical Activity

According to a study, obesity increased the incidence of Diabetic retinopathy in patients with Type 2 Diabetes Mellitus. Physical activity and watching your calories can get you into a healthy weight range and avoid the complications of diabetes mellitus.

Physical activity improves glucose control in Type 2 diabetes mellitus and decreases the risk of cardiovascular disorders, contributes to weight loss and improves well being. DM patients leading a sedentary lifestyle have a higher risk of diabetic retinopathy than those living actively. Less physically active people with diabetes showed increased blood flow in the retina on exertion.

According to data, weight and resistance-based training effectively achieve glycemic control. Aerobics exercises are also suitable for glycemic control. Examples of aerobic exercises include:

• Walking 
• Jogging
• Cycling 
• Swimming
• Rowing
• Zumba

2. Avoid Alcohol Consumption

According to a study, alcohol may lead to a higher risk of deterioration of visual acuity and oxidative stress. These are significantly related to the risk of Diabetic retinopathy. Please note that alcohol addiction may lead to neglect of treatment, thus increasing the risk of DR development.

3. Stimulants

A study shows that tea acts as a potent neuroprotector in the retina. Tea can protect diabetic retinal neurons and thereby prevent diabetic retinopathy. Moreover, a low dose of green tea is likely to increase antioxidant defences. Black tea helps in maintaining proper glycemic control.

Coffee is one of the most consumed beverages worldwide. Coffee contains microelements that show antioxidant effects, such as manganese, zinc, copper and iron. As a result, it helps in decreasing the risk of diabetic retinopathy. 

Summary

Glaucoma is a condition characterised by an increase in the intraocular pressure of the eyes. This increased pressure damages the neuronal and retinal cells, leading to permanent blindness. Diabetes is a condition which causes multiple complications, including Diabetic retinopathy. This condition causes the formation of abnormal blood vessels, which prevent the drainage of the aqueous humour produced by our eyes. Also, it causes an increase in the intraocular pressure leading to secondary glaucoma, also known as neurovascular glaucoma. In this said way, diabetes increases glaucoma risk, significantly decreasing quality of life. To prevent complications of diabetes, it is essential to maintain your blood sugar levels. In addition, specific diet and lifestyle modifications like switching to a Mediterranean diet, including healthy fats, vitamin C rich foods, and physical activity, can decrease the risk of diabetic retinopathy. 

Frequently asked questions (FAQs)

Q. Why does diabetes cause glaucoma?

A.Diabetes causes a set of complications, one of which is diabetic retinopathy. Higher blood sugar levels cause an increase in blood flow, leading to changes in two phases: Non-proliferative and proliferative phases. In the proliferative phase, there is an increase in abnormal blood vessels. These blood vessels obstruct the drainage of aqueous humour, which leads to increased intraocular pressure. As a result, this increase in pressure damages retinal cells and neuronal cells, known as secondary or neurovascular glaucoma.  

Q. Is there a relationship between glaucoma and diabetes?

A.Yes, the relationship between glaucoma and diabetes has been proved in multiple studies. Diabetic retinopathy renders the eye unable to drain aqueous humour. It causes an increase in intraocular pressure and secondary glaucoma. The risk of glaucoma is increased by 1.4 fold in people with diabetes. 

Q. Can diabetic glaucoma be treated?

A. People with diabetes are generally at risk for open-angle glaucoma. Glaucoma is treated the same way as for non-people with diabetes by lowering the eye pressure with medications, laser, and surgery if needed. 

Q. What type of glaucoma do diabetics get?

A.Glaucoma is primarily of 2 types: Open-angle glaucoma and closed-angle/angle-closure glaucoma. Open-angle glaucoma is a condition that occurs over time, whereas angle-closure glaucoma occurs in a very short time and becomes a medical emergency. According to a study, people with diabetes are at risk for open-angle type glaucoma. There is an almost 36% increased chance of getting open-angle glaucoma in people with diabetes. 

Q. Can diabetes affect the optic nerve?

A. According to data, diabetic retinopathy is caused by high blood sugar due to diabetes. Over a while, having too much sugar in your blood can damage your retina. It is the part of your eye that detects light and sends signals to your brain through the optic nerve. It doesn’t directly damage the optic nerve. However, it damages the retina, connected to the optic nerve. 

Q. What percentage of diabetics get glaucoma?

A.Diabetics are at an increased risk of getting glaucoma. However, this does not mean that all people with diabetes will have glaucoma. Maintaining your blood sugar levels and lifestyle modifications can keep diabetic complications away. According to a study, the prevalence of glaucoma in people with diabetes is about 4.96% to 14.6%. 

Q. How can you tell if diabetes is affecting your eyes?

A.According to data, the early stages of diabetic retinopathy usually don’t have any symptoms. However, some people notice changes in their vision, like trouble, reading or seeing faraway objects. In later stages, there might be retinal bleeding. You may see dark, floating spots or streaks that look like cobwebs if this happens.  

Q. What is retinopathy diabetes?

A.Diabetic retinopathy is an eye condition that can cause vision loss and blindness in people who have diabetes. It affects blood vessels in the retina. It has two phases: The nonproliferative and Proliferative phases. 

The nonproliferative stage causes micro-aneurysms and retinal haemorrhages. The proliferative stage forms abnormal blood vessels which bleed easily. 

Q. What does your vision look like with glaucoma?

A.You may see dark, floating spots or streaks that look like cobwebs. You may require more light, and the vision might be blurry, and you might see glare. According to a study, Symptoms reported may have been due to loss of contrast sensitivity, acuity or field. 

Q. Do all diabetics go blind?

A.No, diabetic retinopathy occurs in long-standing cases, that is over 20 years. However, maintaining good glycemic control and lifestyle changes can help prevent diabetic retinopathy. Diabetic retinopathy does not necessarily mean blindness. You can treat it with medications and surgery in the initial stages. 

Q. How long does it take to go blind from diabetes?

A.It depends on your glycemic control and the duration for which you have diabetes. Diabetic retinopathy generally starts after five years of getting diabetes. However, almost all diabetics have retinal damage after 20 years. This may be detected early and corrected to prevent further damage and blindness. 

Q. Which is the first stage of diabetic retinopathy?

A.There are four stages in diabetic retinopathy. They are 

Stage 1 is Mild nonproliferative diabetic retinopathy. Next, stage 2 is Moderate nonproliferative diabetic retinopathy. The stage 3 is Severe nonproliferative diabetic retinopathy. Stage 4 is Proliferative diabetic retinopathy and stage 5 is patients should have a dilated eye examination every 12 months. 

Q. Can glaucoma be stopped?

A. Treatment cannot reverse the damage caused by glaucoma. However, treatment and regular checkups can help slow or prevent vision loss, especially if diagnosed early. Glaucoma is treated by medications, laser or surgery if required.