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According to the 2014 National Diabetes Statistics Report, 29.1 million Americans (9.3% of the population) have diabetes mellitus, including about 8 million people who are undiagnosed.1 The prevalence of diabetes among adults is rising, but what is even more disturbing is the prevalence of diabetes and risk factors such as obesity among young people. A study published this year in the Journal of the American Medical Association found that between 2001 and 2009 there was a dramatic increase in the prevalence of diabetes among those ages 19 and younger, with a 21% increase in type 1 diabetes and a 30.5% increase in type 2.2
DIABETES AND THE EYE
Diabetes is a systemic disease with a long list of associated health conditions, including diabetic retinopathy (DR). Sustained high blood glucose levels in diabetes directly damage the endothelial lining of blood vessels throughout the body, including the retinal microvasculature.
About one-third of diabetic patients (28.5% of those age 40 and older) develop some form of retinopathy.1 DR can occur on a spectrum ranging from very mild, nonproliferative DR to diabetic macular edema (DME), in which compromise of the blood vessels in the macula causes swelling and reduced visual acuity, to proliferative DR, which is characterized by new blood vessel growth, leakage in the retina, and vision loss. At the far end of the scale is high-risk proliferative DR, in which rapid blood vessel growth throughout the retina and the vitreous can cause a retinal detachment and severe visual loss in a short period of time.
It generally takes time for retinopathy to develop, which is one reason that Centers for Disease Control and Prevention statistics on DR are for people age 40 and older. But if we consider that 10- and 15-year-olds are now being diagnosed with type 2 diabetes—something unheard of until quite recently—those patients could potentially develop DR as young adults. There is concern, too, that diabetic youths in high-risk populations may have a higher prevalence of retinopathy. In a recent study, for example, 55% of Hispanic and nonwhite diabetic youths had signs of retinopathy.3
COORDINATING CARE OF DIABETIC PATIENTS
The primary care physician or endocrinologist is typically the driver of diabetic care, referring patients to eye care specialists when necessary and keeping tabs on blood glucose control via hemoglobin A1C testing. This test measures the percentage of glycosylated hemoglobin protein in red blood cells. The higher the A1C level, the greater the risk of diabetic complications. Physicians generally recommend that patients with diabetes aim for an A1C of 7% or lower. I always ask patients with diabetes what their A1C is—even if I already know the answer—because it tells me how engaged they are in their health care.
For diabetic patients with good access to organized health care, blood tests are done at least twice a year, and dilated eye examinations are performed annually starting at diagnosis in adults and within 5 years of diagnosis in children. In my community, there is good adherence to these national guidelines, and primary care providers devote high levels of attention to diabetes. Communication among providers, a crucial element in good outcomes, is relatively robust.
In more transient settings and in communities that lack access to care, however, there may be many more people with undiagnosed disease; diabetic patients who are not compliant with follow-up care; and diabetic patients who are not being seen by any health care provider, let alone presenting regularly for dilated eye exams.
Eye care providers play an important role not only in the management of diabetic eye disease, but as a check on management of the systemic disease as well. That is because the retina provides a unique window into the health of the vasculature. A report of the onset of retinopathy or progression of existing retinopathy can, in some cases, be the first diagnosis of the disease or alert the primary care provider or endocrinologist that all is not well, no matter what the A1C levels suggest.
The development of DR can also serve as an important catalyst for lifestyle change. When I first see early DR in a patient I have been following, I tell that patient, “This is a warning sign. You now know that you are in the one-third of patients who develop retinopathy and have the potential to suffer vision loss. But the good news is that there are things you can do to turn this around.” A diagnosis of DR may be scary enough to motivate the patient to be more compliant or make healthier choices about diet, exercise, and smoking.
At either end of the spectrum of diabetic eye disease, treatment options have not changed much. For early nonproliferative retinopathy, observation alone continues to be the recommendation. For patients with proliferative retinopathy, the mainstay of treatment continues to be panretinal photocoagulation. This procedure essentially cauterizes the peripheral retina, sacrificing peripheral vision to protect central vision.
But for patients with diabetic macular edema—that critical moderate stage—the standard of care is very much still evolving.
The availability of antivascular endothelial growth factor therapies for intravitreal injection has had a huge impact on the care of patients with DME and has rapidly become the first-line treatment for DME. However, antivascular endothelial growth factor agents are not effective for everyone; they do not really address the underlying damage to the retinal vasculature, but rather target only the leakage that results from that damage; also, their effects are not long-lasting. This is particularly problematic when we consider young people now being diagnosed with diabetes who will have to live with its consequences—and the burden of these treatments—for many years.
There are several new agents, drug classes, and drug delivery mechanisms in the pipeline that could improve results or extend efficacy (see Current and Pipeline Treatments for DME).
It is exciting to have better treatment options in the pipeline, but my goal as a physician is for my patients not to need these treatments at all. It is important to renew our focus on patient wellness and prevention, along with better management for those who have diabetes but have not yet developed DR. By being vigilant, helping patients understand the importance of good glucose control, and keeping primary care providers apprised of retinal developments, we can set the stage for better outcomes for our patients. n
Vicken Karageozian, MD, is a partner at Clarity Eye Group in Huntington Beach, California, and is the chief technology officer of Allegro Ophthalmics, makers of the investigational drug Luminate. Dr. Karageozian may be reached at (949) 940-8130; email@example.com.
1. 2014 National Diabetes Statistics Report. Centers for Disease Control. http://www.cdc.gov/diabetes/pubs/statsreport14/national-diabetes-report-web.pdf. Accessed September 24, 2014.
2. Dabelea D, Mayer-Davis EJ, Saydah S, et al; SEARCH for Diabetes in Youth Study. Prevalence of type 1 and type 2 diabetes among children and adolescents from 2001 to 2009. JAMA. 2014;311(17):1778-1786.
3. Mayer-Davis EJ, Saadine J, D’Agostino RB Jr, et al. Diabetic retinopathy in the SEARCH for Diabetes in Youth Cohort: a pilot study. Diabet Med. 2012;29(9):1148-1152.