Diabetic Retinopathy

Diabetes is a chronic disease that is estimated to affect more than 200 million people worldwide and that number is expected to increase by more than 120% by 2025. [3] In the United States, an estimated 29.1 million people, or 9.3% of the total population have either Type 1 or Type 2 diabetes, with nearly one third being unaware that they even have the disease. [1]  

Diabetes can lead to numerous vision problems, even more so when it is poorly controlled. The excess amount of sugar in the blood, causes the blood vessels that supply the eye to thicken and harden, preventing them from functioning properly. The structures of the eye mainly affected by diabetes include the retina (diabetic retinopathy), the crystalline lens (cataracts), the iris (rubeosis – formation of new abnormal blood vessels on the iris surface), and optic nerve (glaucoma). Although diabetes is not a primary cause of cataracts or glaucoma, these eye disorders tend to appear earlier in people with diabetes.

Diabetic retinopathy is an important health concern for people with diabetes, as it is a leading cause of new cases of legal blindness in working-age Americans. It is estimated that by 2020, 6 million people age 40 and over in the United States will have diabetic retinopathy, and for 1.34 million of them it will be sight-threatening. [5]

 

What is diabetic retinopathy?

Diabetic retinopathy is a complication of diabetes that affects the blood vessels of the retina. The retina is a layered structure on the back inside surface of the eye. The retinal tissue is made up of light-sensitive cells that transmit nerve impulses through the optic nerve to the brain, where a visual image is formed.

Diabetic retinopathy can develop in anyone who has Type 1 or Type 2 diabetes, but the risk increases for those who have had diabetes longer, or for those with poorly controlled blood glucose levels. High blood glucose levels, over time, can lead to the blockage of the tiny blood vessels that nourish the retina. When the blood supply is cut off, the eye will attempt to grow new blood vessels to deliver needed blood to the retina. Unfortunately, the newly formed blood vessels are poorly developed, very weak and may easily leak blood (hemorrhage) and other liquid into the retina.    

Diabetic retinopathy may lead to poor vision and over years, may even progress to blindness. Most of the time, it gets worse over many years. Diabetic retinopathy usually affects both eyes.

In some cases, any vision that is lost from diabetic retinopathy is irreversible, however, early detection and treatment can reduce the risk of blindness by 95 percent. [2] 

There are two types of diabetic retinopathy, early stage, non-proliferative (new blood vessels aren't growing), and later stage proliferative (new vessels are growing).  

Non-proliferative diabetic retinopathy (NPDR) is the most common and earliest stage of the disease. People often have no noticeable symptoms. Microscopic changes occur in the blood vessels within the retina and may include microaneurysms (tiny swellings on the side of a blood vessel/artery) that can rupture and leak into the retina. These bursting microaneurysms appear as tiny spots or dots of blood on the retina but can only been seen during an eye exam.

As the severity of non-proliferative retinopathy increases, the risk of developing the sight-threatening form proliferative diabetic retinopathy, also increases. The larger vessels in the retina can also become dilated or irregular. Nerve fibers in the retina may also begin to swell and if this swelling occurs in the macula (central part of the retina) it is referred to as macular edema and will require treatment.

Proliferative diabetic retinopathy (PDR) is characterised by the growth of abnormal new blood vessels (neovascularization) in the retina. New abnormal blood vessels proliferate (increase in number) and are weak and may burst and bleed into the retina or the jelly-like fluid inside the eye (vitreous fluid), causing vision loss. The bleeding may also cause scar tissue to form, which can tug on the delicate layers of the retina, like layers of wallpaper being pulled and peeling away from a wall, creating a retinal detachment. A retinal detachment can lead to permanent vision loss.

 

WHAT CAUSES DIABETIC RETINOPATHY?

Some people have difficulty maintaining their blood sugar levels within a target range. High blood sugar damages the tiny blood vessels of the retina, causing diabetic retinopathy.

For those that already have diabetic retinopathy, also having high blood pressure can cause the retinopathy to become progressively worse. High blood pressure puts more strain on the already week blood vessels, potentially causing more leakage of fluid or blood into the eye.

 

WHO CAN GET DIABETIC RETINOPATHY?

Anyone with diabetes should attend regular dilated eye examinations to check for diabetic retinopathy. Pregnancy may worsen diabetic retinopathy, so when pregnant, it may be recommended to have more frequent eye exams throughout the pregnancy.

Factors that increase the risk of developing diabetic retinopathy:

• Duration of diabetes — the longer you have diabetes, the greater your risk of developing diabetic retinopathy

• Poorly controlled blood sugar level

• High blood pressure

• High cholesterol

• Pregnancy

• Smoking or tobacco use

• African-American, Hispanic or Native American

 

CAN DIABETIC RETINOPATHY BE PREVENTED?

The risk of causing damage to the tiny blood vessels in the eye can be reduced by maintaining blood sugar levels and blood pressure levels within a more normal target range.  

Stopping smoking can also reduce the risk of retinal damage, because smoking has been shown to increase the rate of progression from mild to more severe retinopathy in diabetic eyes. [4]

 

 

Regular eye examinations can detect diabetic retinopathy in the early stages and management strategies can be put in place (treatment or more careful monitoring) before the disease becomes more severe and vision loss or blindness occurs.

WHAT ARE THE SIGNS AND SYMPTOMS OF DIABETIC RETINOPATHY?

Typically, there are no symptoms of diabetic retinopathy until the disease has reached a more severe form and changes in vision have already started to occur.  

As diabetic retinopathy progresses, symptoms may include:

• Blurred vision

• Worsening of vision at night

• Fluctuating vision (better at times, worse at times)

• Problems distinguishing colors

• Floaters (strings or strands moving through your vision)

• Dark or missing areas of vision

• Sudden vision loss

• Eye pain

 

For those people with diabetes it is very important to have regular eye examinations to detect and monitor diabetic retinopathy. When retinopathy is spotted early, it can be treated to help prevent more significant vision loss.

A dilated eye examination by an ophthalmologist or optometrist is the only way to detect diabetic retinopathy. Dilated, means that drops are put in the eyes that will widen your pupils so that the examiner can see through the pupil to the back of the eye, having a clearer view of the retina. Dilated pupils may make eyes very sensitive to light and cause vision to be blurred for several hours afterward. It is often recommended to bring someone to drive after having eyes dilated.  

If people with diabetes notice changes or problems with their vision, it is important to contact their eye care professional right away. Changes such as blurred vision, sudden vision loss, floaters, or eye pain, may signify that damaging changes are occurring in the eye.

 

WHAT ARE THE TREATMENTS FOR DIABETIC RETINOPATHY?

There are different treatments available for diabetic retinopathy that may slow the progression of vision loss, but there is no cure. Treatments include drug treatment, surgery, and laser treatment. Treatment recommendation depends largely on the type of diabetic retinopathy and severity.

Once someone has received treatment, regular eye examinations will be required and it is likely that in the future, additional treatment may be required.  

Most people require ongoing treatment and monitoring, increasing in frequency as the disease becomes more severe.  

For mild or moderate non-proliferative diabetic retinopathy, treatment may not be required immediately, but ongoing close monitoring by an eyecare professional will be required to determine when treatment is needed.   

Maintaining regular visits with the endocrinologist (diabetes physician) will help to determine if there are options available to better control blood sugar levels. For mild or moderate diabetic retinopathy, good control of blood sugar can help to slow retinopathy progression.

If proliferative diabetic retinopathy or macular edema has occurred, prompt treatment and careful monitoring are required.  

 

TREATMENT OPTIONS MAY INCLUDE:

Laser photocoagulation – Leaking blood vessels are treated with focussed laser burns. Also referred to as ‘focal laser treatment’. Laser photocoagulation can stop or slow the leakage of blood and fluid in the eye. This treatment can usually be performed at your ophthalmologist’s office in a single visit.

Panretinal photocoagulation – Abnormal or large blood vessels can be reduced in size by laser burns applied in a scatter pattern over an area of the retina. Treatment involves making 1,000 to 2,000 tiny laser burns in areas of the retina away from the macula. These laser burns are intended to cause abnormal blood vessels to shrink. Although treatment can be completed in one session, two or more sessions are sometimes required. While it can preserve central vision, scatter laser treatment may cause some loss of peripheral (side) vision, color perception, and night vision. This treatment may require two or more visits to complete and can usually be performed at your ophthalmologist’s office.

Eye injection - Injecting medicine into the vitreous of the eye (intraocular or intravitreal injections) may help to stop the growth and formation of the new, harmful blood vessels. The class of medications are vascular endothelial growth factor (VEGF) inhibitors or anti-VEGF, and they block the growth factor signals in the eye, naturally produced by the body, that are stimulating the growth of the new blood vessels. Studies have shown that anti-VEGF treatment is effective in the treatment of diabetic macular edema, and for slowing progression of diabetic retinopathy. Anti-VEGF injections are increasingly used as a first-line treatment for proliferative diabetic retinopathy.  

Available anti-VEGF drugs used for the treatment of proliferative diabetic retinopathy, among other eye conditions include; Lucentis® (ranibizumab), Avastin® (bevacizumab), and Eylea® (aflibercept). Lucentis® and Eylea® are approved by the U.S. Food and Drug Administration (FDA) for treating eye conditions, and Avastin® was approved to treat cancer, but is commonly used to treat eye conditions. The different drugs vary in cost and frequency they need to be re-injected, so it is important to discuss all these factors with your ophthalmologist.  

Most people will require monthly anti-VEGF injections for the first six months of treatment and less frequently after.    

Eye injections may be done in combination with laser photocoagulation or on their own.  

Vitrectomy – A small incision is made into the eye to carefully remove blood or scar tissue from the vitreous (jelly-like substance in the middle of the eye). This procedure is typically performed in a hospital or surgical center under general or light anesthesia. Vitrectomy surgery can often slow or stop diabetic retinopathy progression, but because diabetes is a lifelong condition, it is likely that retinal damage requiring further treatment will be possible in the future.

 

REFERENCES:

[1] Beckles GL, Chou CF.  Disparities in the Prevalence of Diagnosed Diabetes - United States, 1999-2002 and 2011-2014.  MMWR Morb Mortal Wkly Rep. 2016 Nov 18;65(45):1265-1269.  https://www.ncbi.nlm.nih.gov/pubmed/27855140

[2] The Diabetic Retinopathy Study Research Group Indications for photocoagulation treatment of diabetic retinopathy: Diabetic Retinopathy Study Report no. 14. Int Ophthalmol Clin. 1987;27(4):239–53.  https://www.ncbi.nlm.nih.gov/pubmed/2447027

[3] International Diabetes Federation. IDF diabetes Atlas. 6th edn. Brussels, Belgium, 2013. https://www.idf.org/e-library/epidemiology-research/diabetes-atlas/19-atlas-6th-edition.html

[4] Klein R, Klein BE, Moss SE, Cruickshanks KJ.  The Wisconsin Epidemiologic Study of diabetic retinopathy. XIV. Ten-year incidence and progression of diabetic retinopathy.  Arch Ophthalmol. 1994 Sep;112(9):1217-28.  https://www.ncbi.nlm.nih.gov/pubmed/7619101

[5] Zhang X, Saaddine JB, Chou CF, Cotch MF, Cheng YJ, Geiss LS, Gregg EW, Albright AL, Klein BE, Klein R. Prevalence of diabetic retinopathy in the United States, 2005-2008. JAMA. 2010 Aug 11;304(6):649-56. https://www.ncbi.nlm.nih.gov/pubmed/20699456