For patients with diabetes, becoming blind is at the top of their list of fears, higher than even amputations. In fact, many of my patients tell me that they would rather have a heart attack and die than go blind. An international survey based on experiences with diabetic microvascular complications found that 2 of the 4 top concerns of patients with diabetes are vision-related, the first being blindness and the fourth being other eye problems such as blurriness and cataracts (Figure 1).1

There have been many quality-of-life studies that have been conducted, including one by Brown et al2 that was a time-tradeoff utility value analysis and in which patients were asked to rank the impact of vision loss. These answers were then compared to other systemic conditions regarding the perceived impact on quality of life (Figure 2). In other studies by Brown et al,3,4 patients were asked how many years of life would they be willing to give up to have good vision. Visually impaired patients from diabetic retinopathy were willing to trade years of remaining life for normal vision, and the worse the vision was, the more time patients said they would be willing to trade (Figure 3).

It is not a surprise that patients consider loss of vision as having such a great impact on their quality of life. Vision affects both ambulatory and vehicle mobility, specifically recognition of landmarks and street signs. It also has a direct effect on the ability to read or perform close work, which encompass the activities of daily living such cooking, shopping, and paying bills. Patients with reduced vision have difficulty performing tasks involved with self-care such as reading medicine or food labels and preparing for insulin injections or glucose testing. Finally, patients with vision loss often shy away from social participation or dependence on others, which can result in feelings of vulnerability, depression, and emotional distress.5,6

RISKS FOR PROGRESSION TO DIABETIC RETINOPATHY

As an endocrinologist, I spend much of my time tackling issues such as insulin resistance and vascular disease. When considering the elemental issues in diabetes, however, the main goal is to maintain normal glucose levels. Recently, although I do not have diabetes, I chose to start wearing a continuous glucose monitor to gain a better understanding of the technology. I was fairly surprised at how normal “normal” is—my levels stayed within 70-120 mg/dL throughout the day. Our patients with diabetes, however, begin the day with high levels, and continue to have high blood glucose levels all day long (Figure 4). To achieve normal levels is difficult, particularly because insulin use increases hypoglycemia. Many of our patients will develop some diabetic retinopathy over time. It is estimated that approximately 40% of patients with diabetes aged 40 years or older will develop diabetic retinopathy and that approximately 20% of those patients will have visionthreatening disease.7

We know that longer duration of disease and higher A1C levels are directly associated with a higher risk of developing diabetic retinopathy (Figure 5). In a study by Tapp et al,8 the authors surveyed 11 247 adults older than age 25 in Australia, including 2476 participants with diabetic complications. They found that at all levels of glycemic control, the likelihood of diabetic retinopathy increased with duration of disease. Looking at patients with Type 1 diabetes vs Type 2 vs Type 2 taking insulin, the prevalence of diabetic retinopathy (not necessarily vision threatening) is highest in patients with Type 1 diabetes (Figure 6).9,10

In the Diabetes Control and Complication Trial (DCCT)11 and the United Kingdom Prospective Diabetes Study (UKPDS),12 there was a clear relationship between A1C levels and the risk of developing retinopathy (Figure 7). The challenge is that as A1C levels go down, the risk for severe hypoglycemia goes up, requiring additional intervention (Figure 8).13 Thus, it is important to find a balance for our patients to both reduce the risk of diabetic retinopathy and hypoglycemia. Other more recent studies, such as the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial,14 show a similar relationship between lipids and the progression to diabetic retinopathy.

With regard to intervention, there is a real difference in terms of progression to retinopathy. The data from the DCCT shows that a benefit to both primary and secondary early intervention (Figure 9).11 The durability of intervention is demonstrated in the UKPDS15 and the followup study to the DCCT, the Epidemiology of Diabetes Interventions and Complications trial,16 both of which showed that glycemic control over an extended period of time leads to a continued benefit.I have seen many patients who have been put on an angiotensin-converting enzyme (ACE) inhibitor, not because they have nephropathy or even hypertension, but as a preventive measure. Recently, a study was performed to evaluate the renal and retinal effects of enalapril and losartan in patients with Type 1 diabetes.17 Some of the patients had some form of retinopathy upon study entry, but none had nephropathy. The progression of nephropathy and the development of microalbuminuria was approximately the same with enalapril and placebo, but was higher in patients using the angiotensin-receptor blocker losartan. The progression of retinopathy was slowed by both the ACEinhibitor and the angiotensin receptor blocker, suggesting that an ACE-inhibitor may be a good preventive measure against retinopathy, even in the absence of nephropathy.SUMMARY

Among the current management recommendations for diabetic retinopathy, screening is of utmost importance, as is referral to an ophthalmologist, but it is also important to understand the importance of glycemic and blood pressure control, as well as interventions that can reduce the risk of progression to diabetic retinopathy.

Anne Peters, MD, CDE, is Director, Clinical Diabetes Programs, and a Professor at University of Southern California Keck School of Medicine in Los Angeles.

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