Eye Disease in Type 1 Diabetes Avoided, But How and Why?
One of the most common side effects of type 1 diabetes is eye disease or diabetic retinopathy, which refers to a number of vision problems affecting the retina. But some people with type 1 diabetes have managed to completely or nearly avoid developing this eye disease--but how and why?
Diabetes eye disease causes vision loss
Nearly 90 percent of people who have type 1 diabetes for 20 years or longer develop diabetic retinopathy, which is also the leading cause of vision loss among working age adults in developed countries, including the United States. Among all Americans who have either type 1 or type 2 diabetes, 40 to 45 percent have some degree of diabetic retinopathy, according to the National Eye Institute.
At Joslin Diabetes Center, investigators have reported on a study of 158 people who reached a special milestone: they have had type 1 diabetes for 50 years or longer, and a high proportion of them have developed little or no diabetic retinopathy. These individuals are known as "50-year Medalists," and the research into this special group has been supported by the Juvenile Diabetes Research Foundation (JDRF).
While this finding is remarkable, it begs the question, "How and why have these individuals avoided diabetic retinopathy?" A brief explanation of what diabetic retinopathy is may be helpful.
What is diabetic retinopathy?
Diabetic retinopathy is an umbrella term for a group of eye disorders that commonly develop as a complication in people who have diabetes. Specifically, diabetic retinopathy causes changes in the blood vessels of the retina, which may include swelling, leakage of fluid, or an abnormal growth of new blood vessels on the surface of the retina.
Individuals with diabetes are more likely than people without the disease to develop cataracts, which is a clouding of the eye's lens. People with diabetes are also nearly twice as likely to develop glaucoma, which is an increase in fluid pressure inside the eye that leads to damage to the optic nerve and loss of vision.
Diabetic retinopathy typically occurs in four stages:
- Mild nonproliferative retinopathy is the earliest stage, during which small swellings appear in the retina's blood vessels
- Moderate nonproliferative retinopathy is characterized by the blockage of some blood vessels that supply the retina with nourishment
- Severe nonproliferative retinopathy is characterized by an increase in the number of blocked blood vessels, which then prompts the retina to send signals to the body that it needs more blood vessels
- Proliferative retinopathy is the most advanced stage and is characterized by the growth of new blood vessels, which appear along the retina and the gel that fills the inside of the eye. These blood vessels have fragile walls, and if they leak blood, individuals can experience severe vision loss or blindness.
The diabetic eye disease study
According to Helen Nickerson, JDRF's senior scientific program manager of complications therapies, "The understanding that these Medalists have been relatively unaffected by such a common complication leads us to infer that there may be biological or genetic protective factors that could be utilized to benefit other people with type 1 diabetes."
Although the study findings leave many questions unanswered, Dr. Jennifer Sun, co-investigator of the study, noted that among the Medalists who didn't develop advanced diabetic eye disease, "there was no evidence of substantial DR regression, but the progression of retinopathy seems to slow after about four years in comparison to those who do develop advanced DR."