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Diabetic Eye Care

Diabetes mellitus is a disease with a massive disease burden across the globe. Data shows that in the year 2019 alone, there were 463 million adults within the 20-79-year age group suffering from diabetes worldwide. Not only that, according to the scientific predictions, this number will most likely rise to at least 700 million by the year 2045.(1)

Most people develop eye complications related to diabetes mellitus after having the disease for about 10-15 years. Since the prevalence of the disease is increasing quite dramatically, we find more and more people at the risk of developing diabetic eye diseases every day.

How does the diabetic eye disease occur?

We all know that diabetes is a disease condition which increases sugar levels in the body. Increased glucose levels affect different systems and organs inside the body in multiple ways bringing about changes in both the structure and function. Similarly, a series of changes happen inside the human eye too.

As we know it, the human eye is a globe-like structure covered in many layers. The outermost layer of the eye forms a clear and curved structure in the front side, also known as the cornea. This cornea together with the eye lens direct light rays coming from the surrounding environment in to the eyeball allowing to fall on a screen-like structure called the retina. Retina also has a specialized area responsible for fine vision, and it is called the macula.

For light rays to reach the retina, first they must travel through two fluid-filled chambers; the anterior chamber and the posterior chamber aka the aqueous humor and vitreous humor respectively.

Once the image is focused on the retina, it creates a bunch of electrical signals which travel to the brain via the optic nerve. It is only after the brain processes the information it has received; we get the perception of vision. This is a very quick and a bit complicated process.

Any changes to these finite structures along the visual pathway can cause a great impact on the overall process of vision. Diabetes can affect different components of the eye in a variety of ways. Let’s have a look at a few common eye diseases that occur as a result of diabetes in individuals.

Cataract

Although cataract is a very common disease condition in the eye that even the non-diabetics can easily get, it has been observed that a majority of individuals with diabetes mellitus are more likely to develop cataract at some point or another in their lives. That’s also at an earlier stage of life than the rest of the general population.

In cataracts, the eye lens becomes opaque as a result of denaturation of proteins and other components in the lens of the eye. This process can accelerate as a result of increased glucose levels in the body.

There’s even an acute version of cataract which can occur quite suddenly, in diabetics with very poor glycemic control over a very long period of time. It is also called snow flake cataract.

This occurs as a result of fluctuating levels of blood glucose concentrations which can lead to subsequent osmotic changes in the eye lens affecting its ability to refract. Glucose is an osmotic substance which can draw water into the eye lens, causing it to swell.

In individuals with such fluctuating levels of blood glucose, their ability to read can alter from time to time accordingly. But the good news is, this condition can be easily reversed with good metabolic control of diabetes.

Glaucoma

In glaucoma, the pressure inside the eye increases causing damage to the retina and the optic nerve. This is a very serious disease condition that can lead to even blindness.

Scientific studies show that the individuals with diabetes are more likely to develop glaucoma than those who are not.(2) Increased oxidative stress and increased cellular death which occur as a result of diabetes is responsible for this relationship between the two disease conditions.

Diabetic Retinopathy

Diabetic retinopathy is an umbrella term used to describe damages caused by diabetes to the retina and the iris of an individual. It is also the most commonly diagnosed diabetes-related complication. It is believed that at least 20-30% of people with type-2 diabetes have retinopathy at the initial diagnosis.(3)

What diabetes does is that it brings about a spectrum of changes in micro-blood vessels supplying the eyes. These changes can occur either in the peripheral retina or in the central retina/macula.

Diabetic retinopathy could be either proliferative or non-proliferative in nature. When increased blood sugar level causes damage to the walls of the small blood vessels, it leads to the formation of microaneurysms in the retina.

When these aneurysms burst, bleeding occurs inside the eye, leaving behind protein and lipid deposits as hard exudates, after the blood is cleared out. This is what happens in the non-proliferative stage.

In the proliferative stage, new blood vessels start to grow in the retina as a result of the release of vascular growth factors like VEGF. These factors get released mainly due to the lack of blood supply or ischemia caused by retinal bleeding. Vascular damage is the main culprit behind these changes.

These newly formed blood vessels are very fragile and they can easily rupture with shear stress. These bleedings often resolve with fibrous or scar tissue formation in the retina. This greatly affects the overall quality of vision.

There is a slight difference in the pathogenesis of the disease in the macular area of the retina as its anatomy is slightly different from the rest. Here macula oedema occurs as the process of clearance of exudates does not happen properly. Due to this macula swelling, macula becomes thick and distorted leading to loss of the central vision.

Diagnosis

A detailed eye examination is a must for detecting diabetic eye diseases. After obtaining a detailed history of the patient inquiring about the duration of diabetes, the presence of any visual disturbances, and the presence of any other co-morbidities, a thorough eye examination can be carried out.

Following aspects should be prioritized in an eye examination;

As alternative and novel methods of diagnosis Fluorescein angiography can be done as well.

How diabetic retinopathy is treated?

The treatment modality varies according to the type of the eye disease. For example, cataract is treated with extraction and implantation of the eye lens.

On the other hand, proliferative retinopathy is treated with the use of laser photocoagulation therapy, which involves destroying newly formed blood vessels by directing a laser beam at them. Vitreoretinal surgery is another option available in place of laser treatment and it is for treating recurrent bleeding inside the eye.

Besides, there are new ways of controlling diabetic retinopathy and diabetic maculopathy with use of anti-VEGF drugs such as bevacizumab, ranibizumab and aflibercept.

What puts you at more risk of developing the diabetic eye disease?

What are the red flag signs indicating diabetic eye disease?

Unfortunately enough, a majority of eye diseases due to diabetes do not come with a set of warning signs beforehand. By the time the symptoms start to appear, the disease could already be at a quite advanced state.

Here are some of the symptoms that might appear earlier and help you identify whether you have some kind of disease condition in your eyes or not.

Tips to prevent or delay diabetic eye complications

Diabetic eye diseases can be easily prevented or delayed if you take good care of your eyes. Here are a few useful tips that will help you keep your eyes healthy.

Get regular eye screenings

Getting your eyes examined for the presence of diabetic eye disease, at least once a year is really important for maintaining your eye health!

According to the International Council of Ophthalmology’s guidelines for diabetic eye care, minimum components of an eye screening should include a screening visual acuity exam and a retinal examination.(4)

A properly trained person must conduct the screening process for visual acuity. Usually, this is done with the help of 6/12 (20/40) equivalent handheld chart which have at least 5 standard letters or symbols. A pin-hole option can be used if visual acuity is reduced.

On the other hand, a retinal examination must consist of either a direct/indirect ophthalmoscopy or slit-lamp examination of the retina. Retinal photography with optical coherence tomography (OCT) scanning is another option available.

A comprehensive eye screening process must include blood glucose, serum lipids, and blood pressure testing as well.

If the visual acuity and retinal examination are unsatisfactory, you should consult an ophthalmologist for further opinion.

The frequency of eye screening and follow-up varies according to the initial findings of the eye examination.(4)

Maintain proper glycemic control

Having sky-high blood sugar levels puts you at more risk of developing diabetic eye disease. Increased glucose level in the blood alone can result in blurred vision as it has the ability to affect the eye lens even without micro-vascular changes.

Although visual disturbances due to changes in the eye lens are reversible, if damage occurs to the tiny blood vessels in your eyes, it could last a lifetime.

Therefore, it is crucial to take your diabetic medications or insulin properly and maintain those sugar levels well under control!

Control high blood pressure

Uncontrolled blood pressure can become an added risk factor for diabetic eye disease. Therefore, it is important to maintain your blood pressure well under the recommended values.

According to the current American Diabetes Association (ADA) guidelines, individuals with diabetes must try to maintain the systolic blood pressure at least under 140 mmHg and the diastolic blood pressure under 90 mmHg. Those who are at higher risk of developing cardiovascular diseases may require more strict blood pressure control to at least less than 130/80 mmHg. (5)

Maintain healthy blood cholesterol levels

Increased cholesterol level in the blood can accelerate the process of diabetic retinopathy. Furthermore, studies show a significant drop in the vision of individuals who are with elevated cholesterol levels for a longer duration of time.(6) So, maintaining serum lipid levels at a healthy range will help you keep your eyes healthy.

Quit Smoking

There’s plenty of scientific evidence to show the link between smoking and the occurrence of diabetic eye complications such as cataract, glaucoma, diabetic retinopathy, and dry eye syndrome.(7) Not only that, smoking could act as a trigger for the premature development of other microvascular complications as well. Therefore, it is always better to get rid of this unhealthy habit of smoking!

Exercise Regularly

Exercising regularly means you are trying to keep your body fit. You are burning those extra calories and excess sugar in your blood. Studies show that higher levels of physical activity relates to reduced signs of retinal microvascular disease.(8) Even if you happen to get diabetic eye diseases at some point or another, if you are someone with satisfactory physical activity, you are most likely to get a less severe version of the disease than those who are physically inactive.

Eye complications can affect any individual who has diabetes mellitus for a longer duration time. Although it is not entirely avoidable, with right glycemic control, the onset and the progression of these eye conditions can be altered to gain the best health outcomes.

Apart from achieving good glycemic control, it is crucial to undergo regular eye screening and examination to detect eye diseases at an early stage instead of ending up at an advanced stage where you can’t do anything about it.

Since it is none other than your vision is at the stake, taking all the necessary precautions to protect your eyesight from diabetes-related complications should be given the highest priority.

References

1.         Facts & figures [Internet]. [cited 2021 Feb 12]. Available from: https://www.idf.org/aboutdiabetes/what-is-diabetes/facts-figures.html

2.         Song BJ, Aiello LP, Pasquale LR. Presence and Risk Factors for Glaucoma in Patients with Diabetes. Curr Diab Rep. 2016;16(12).

3.         Kumar and Clark’s Clinical Medicine – 9th Edition [Internet]. [cited 2021 Feb 13]. Available from: https://www.elsevier.com/books/kumar-and-clarks-clinical-medicine/kumar/978-0-7020-6601-6

4.         Mcswiney FT, Wardrop B, Hyde PN, Lafountain RA, Volek JS, Doyle L. endurance athletes. Metabolism [Internet]. 2017;81:25–34. Available from: https://doi.org/10.1016/j.metabol.2017.10.010

5.         International council of Ophthalmology. ICO Guidelines for Diabetic Eye Care. 2014;(February):32. Available from: http://www.icoph.org/downloads/ICOGuidelinesforDiabeticEyeCare.pdf

6.         Atchison E, Barkmeier A. The Role of Systemic Risk Factors in Diabetic Retinopathy [Internet]. Vol. 4, Current Ophthalmology Reports. Springer Verlag; 2016 [cited 2021 Feb 14]. p. 84–9. Available from: /pmc/articles/PMC5432556/

7.         Sliwinska-Mosson M, Milnerowicz H. The impact of smoking on the development of diabetes and its complications. Diabetes Vasc Dis Res. 2017;14(4):265–76.

8.         Tikellis G, Anuradha S, Klein R, Wong TY. Association between physical activity and retinal microvascular signs: The atherosclerosis risk in communities (ARIC) study. Microcirculation [Internet]. 2010 Jul [cited 2021 Feb 14];17(5):381–93. Available from: /pmc/articles/PMC3005356/