About 1.5 million Americans are newly diagnosed with diabetes every year. In 2015, over 30 million Americans had diabetes, with almost a third (10 million) not even aware they had the disease. In the same year, about a quarter of a million deaths in the US were attributed to diabetes, with this disease being considered the seventh leading cause of death in the nation. For reference, heart disease is the leading cause of death and Alzheimer’s is the 6th leading cause.

Diabetic Retinopathy is a Leading Cause of Vision Impairment in Working-Age Adults
Many Americans, whether diabetic or not (or unknowingly diabetic), do not realize that diabetes can manifest in the eye. It is often said that the retina of the eye is the only place in the body where blood vessels can be seen live, in vivo, without having to undergo any invasive medical procedures. While some patients may argue that shining dazzling lights into the eye is, in fact, quite invasive, especially if the eye care practitioner’s face is within kissing distance of yours, performing a diabetic eye test can provide some useful information about the rest of the body.

Diabetic eye disease can appear in a few different ways. One of the leading causes of vision impairment in working-age adults is diabetic retinopathy, which is damage to the small blood vessels of the retina due to the chronically elevated blood glucose levels found in diabetes. As the retina is the sensory layer of tissue lining the inside of the eyeball that detects light, disease of this part of the eye can very easily cause vision loss. This is the case particularly if the macula, the anatomical part of the eye dealing with fine detailed central vision, is involved in what is known as diabetic macular edema. Diabetes is also associated with the formation of cataract and can double the risk of glaucoma.

Diabetic retinopathy can manifest as leakage of fluid and blood through damaged retinal blood vessel walls. This can be seen as yellowish white patches known as exudate as or little spots of hemorrhages throughout the retina. Microaneurysms forming on a weakened vessel wall can also occur. Dot/blot hemorrhages, as they’re called, and microaneurysms can be difficult to detect unless dilating eye drops are instilled to widen the pupil for a better view of the retina – try spotting a tiny red dot against an orangey-red background through a little round window! It’s like playing Where’s Waldo in a sea of red and white stripes through a little porthole using a flashlight at night time. Yes, that was specific but also a moderately accurate and descriptive parallel to what your eye care practitioner is doing when he or she looks for early diabetic retinopathy. In severe cases, diabetic retinopathy can progress to a stage known as proliferative diabetic retinopathy. This is when the retina is so unhealthy that new blood vessels begin to grow throughout the inside of the eyeball. These new vessels are fragile and poorly formed, and are at greater risk of hemorrhaging, and this time more than just a little spot of blood – this time more like playing Where’s Waldo in that sea of red and white stripes but Waldo is a giant and staring right at you. The scar tissue around these new blood vessels can also contract, similar to scars on the skin, causing distortion, tearing, or detachment of the surrounding retinal tissue.

The presence and severity of diabetic retinopathy is associated with several risk factors, some of which are modifiable.

• Hispanic Americans and African Americans have been found to have a higher risk of both diabetes and diabetic retinopathy compared to Caucasian Americans, with 84% and 46% higher rates of prevalence respectively. In a US study conducted in 2010, almost 20% of Latinos had retinopathy compared to less than 10% of Caucasians.  In general, the rates of diagnosed diabetes are higher in Hispanics and African Americans compared to other ethnic backgrounds in the US.

 

• The duration of diabetes is strongly associated with the presence of retinopathy, particularly after 10 years. A study conducted in Wisconsin found that patients living with diabetes for 15 years had a prevalence of retinopathy of 80%. This risk factor applies to both types 1 and 2 diabetes.

 

• Elevated cholesterol levels (hypercholesterolemia) has been an inconsistent finding in association to retinopathy, with some researchers publishing results which show it is a risk factor while others find it unrelated. However, higher total serum cholesterol levels have been linked to diabetic macular edema and it is still considered best practice to address high cholesterol levels in diabetic patients.

 

• Hypertension is unquestionably related to the prevalence of retinopathy and can play a part in any stage of eye disease, from mild retinopathy to severe proliferative retinopathy.

 

• Control of high blood glucose levels (hyperglycemia) is also an important factor in the presence and severity of diabetic retinopathy. A blood test known as HbA1c measures the amount of glucose over the preceding three months to give a more accurate indication of the blood glucose control compared to the daily finger prick test. Studies have found that HbA1c measurements over 7% are linked to increased risk of some degree of retinopathy in both type 1 and 2 diabetes.

The type of diabetes, gender, and body mass index have not been found to be associated with the risk of diabetic retinopathy.

Depending on the specifics of the presentation in each individual case of diabetic eye disease, management and treatment can vary. Progression of retinopathy has been recorded in diabetic patients undergoing cataract surgery, as well as an increased incidence of diabetic macular edema. In mild cases of non-proliferative retinopathy, your eye care practitioner may elect to just review frequently to ensure it is resolving and not worsening. In a lot of these early retinopathy cases the concern is not so much for the vision or the eyes but more about what these findings in the eye indicate about the overall blood glucose control and what may been happening in other vital organs of the body – you can survive without an eye but not without at least one functioning kidney. In vision-threatening cases a laser treatment may be applied to hemorrhaging blood vessels to seal them off, or if proliferative retinopathy or macular edema is diagnosed, the first-line treatment is a course of injections into the eye.

Needless to say, the best way of avoiding diabetic eye disease is to avoid getting diabetes in the first place. If you are one of the 30 million Americans already living with diabetes, the second best way of avoiding diabetic eye disease is to control your blood glucose and blood pressure. And though being dazzled by bright lights may not be the most fun and neither is playing Where’s Waldo in a sea of red and white stripes through a little porthole – scheduling regular diabetic eye tests with your eye care practitioner is definitely higher on the list than the seventh best way of avoiding vision loss from diabetic eye disease.

References
Statistics About Diabetes. http://www.diabetes.org/diabetes-basics/statistics/
The Top 10 Leading Causes of Death in the United States. https://www.medicalnewstoday.com/articles/282929.php
Facts About Diabetic Eye Disease. https://nei.nih.gov/health/diabetic/retinopathy
Global Prevalence and Major Risk Factors of Diabetic Retinopathy. http://care.diabetesjournals.org/content/diacare/35/3/556.full.pdf
Risk Factors for Diabetic Retinopathy: a case-control study. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5088444/
Diabetic Retinopathy Before and After Cataract Surgery. http://bjo.bmj.com/content/80/9/789.short