Diabetes Mellitus/Diabetic Retinopathy
Title: Diabetes Mellitus/Diabetic Retinopathy
Author: E Anne Shepherd, 4th Year Medical Student, University of Tennessee Health Science Center
Diabetes Mellitus is a medical condition that is seen and managed by every primary care physician and specialist around the world. According to data from the CDC in 2012, 29.1 million Americans (9.3% of the population) had received the diagnosis of diabetes and there are an estimated 1.4 million new diagnoses every year. 86 million Americans twenty years or older were categorized as “prediabetic”, which is increased from 79 million in 2010. The cost of diabetes was $245 billion in 2012 and the average medical expenditures of a diabetic patient was 2.3 higher than a nondiabetic counterpart. Diabetes plays a major role in care and management of many of our patients.
One of the main complications in diabetes is microvascular disease, which includes diabetic retinopathy, nephropathy, and neuropathy which lead to vision loss, end stage renal disease, and lower limb ulcers or amputations, respectively. This article is focused on diabetic retinopathy but it is important to understand that all microvascular diseases stem from the same processes which are happening throughout the entire body. The risk of developing retinopathy, as well as the other microvascular complications, is determined by the duration and severity of the hyperglycemia. In type I diabetes the onset is usually within fifteen to twenty years while in type II diabetes retinopathy can be seen even before the official diagnosis. It is important that both type I and II diabetic patients are counselled on the importance of yearly eye exams by an ophthalmologist.
There are multiple mechanisms at play in a diabetic patient that lead to retinopathy, including osmotic stress from sorbitol accumulation, injury from advanced glycosylated end products, oxidative stress from free radicals, and growth factors like vascular endothelial growth factor (VEGF).
The two main categories of diabetic retinopathy are nonproliferative diabetic retinopathy and proliferative diabetic retinopathy, which require separate treatment regimens. Nonproliferative diabetic retinopathy is characterized by leaky blood vessels causing macular edema. These vessels are often fragile and lead to small hemorrhages, called dot hemorrhages, and microaneurysms in the retina. Edema within the macula (the part of the retina responsible for central vision) can cause blurred vision and is now treated with an anti-VEGF intraocular injection, such as ranibizumab (Lucentis) or bevacizumab (Avastin). Proliferative diabetic retinopathy is characterized by the formation of new blood vessels in response to retinal ischemia. White areas in the retina, called “cotton wool spots”, are localized regions of ischemia and can be an early sign of proliferative retinopathy. Advance proliferation can lead to vitreous hemorrhages and retinal detachments. Patients should be explained the signs of retinal detachment, like increased floaters/flashes or the sensation of curtains being pulled over their eyes, and to call their ophthalmologist if they experience any of these. Proliferative diabetic retinopathy is treated with laser panretinal photocoagulation (PRP) to halt further progression of vision loss.
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