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Diabetes Mellitus and Diabetic Retinopathy (Diabetes)

Why is diabetes so common, and why are its effects so severe?

Diabetes remains the most common cause of blindness in the United States in young to middle aged adults for three main reasons:

Diet: Controlling diet is difficult.

False optimism: Most patients believe they have a milder type of diabetes early on, but it advances to affect the body’s blood circulation, which damages the kidneys, eyes, brain and heart.

Delayed effects: Patients feel no ill effects for years while their sugar is out of control. Only much later will the damage manifest as complications in health.

The delay in "punishment” from high blood sugar means that early warning and adjusted diet are essential to prevent diabetes from ravaging the body. Patients must understand that years of high blood sugar caused by poor diet results in blindness, strokes, heart attacks, and loss of limbs.

Sometimes witnessing a loved one succumb to diabetes, experiencing kidney failure, amputation or blindness will cause a patient to improve their diet and blood sugar control. But because the realities of future damage are often not fully understood, patients don’t manage their blood sugar properly. This continues until they experience vision loss, a heart attack, or kidney failure, and though they respond with diet management, the majority of damage has been done and further loss will likely ensue.

How does a disease of increased blood sugar complicate health?

When sugar is too high in the blood it damages the blood vessels.  The capillaries-- the smallest blood vessels in the body-- deteriorate over years of poor sugar control. In addition, pericyte support cells that help repair blood vessels die off, accumulating damage over time. Most of the damage is not reversible, although better sugar control usually decreases the severity of the problems.

The nature of the disease carries a momentum that too often runs its course despite medical advice and treatment. Loss of function often occurs during the prime years of a patient’s life, starting as a young adult through their middle-aged years and beyond.

How does diabetes result in vision loss?

Long term blood vessel damage results in the eyes not receiving proper nutrition and accumulating waste that would normally be disposed of. Early changes that appear in the eyes of diabetic patients are called background diabetic retinopathy.  These are hemorrhages, small aneurysms, and small infarcts of the retina that can be seen in exams or photographs.  

Proliferative diabetic retinopathy with large leashes of new blood vessels

Proliferative diabetic retinopathy with large leashes of new blood vessels

The blood vessels at this stage are like garden hoses that have small holes along their course. These damaged vessels leak fluid throughout their length, where normally they should only exchange nutrients and waste at the capillaries (the end of the hose).  These leaks allow blood, cholesterol and watery serum to leak out into the retina. The fluid distorts the shape of the retina and short-circuits the retinal neural network, resulting in loss of vision.

Severe diabetic traction retinal detachment

Severe diabetic traction retinal detachment

When this happens on the macula, the location of the retina responsible for our center of vision, it is known as macular edema. The irregular pooling of fluid in the macula disrupts a delicate structure vital to normal vision. It is difficult to cure and can last for months to years even with aggressive treatment.

If sugar remains out of control the patients may progress to the next stage called proliferative diabetic retinopathy, which includes bleeding into the vitreous cavity of the eye and “new” growth of fibrous blood vessels from the retina.

Often despite the physician’s best efforts, the patient continues living with vision loss even after all possible treatment is given.

How is diabetic vision loss treated today?

Treatments for leakage of fluid and macular edema involve light laser to the macula, injection of anti-vegf agents directly into the vitreous cavity of the eye, and injection of steroids around or directly into the eye.

When bleeding occurs in proliferative diabetic retinopathy, heavy laser called pan retinal photocoagulation (PRP) is used to burn the peripheral retina causing the new blood vessels to shrink back.  Anit-vegf injections can also be used, but last only 6 to 10 weeks, and need to be repeated frequently to suppress the new growth of blood vessels until laser treatment is possible.  Retinal surgeons remove the resulting blood and scar tissue to improve vision.

Almost every tool a retinal surgeon has may be used to treat diabetic retinopathy, and often ophthalmologists combine treatments because complications occur simultaneously.

For the patients that have advanced diabetes, the field of vitreoretinal surgery and other medical treatments continue to grow and evolve.

Nevertheless, the best way to treat diabetic retinopathy is to prevent it from occurring by educating and encouraging diabetic patients to protect their circulation early on with good diet and an exercise program.