August 07, 2018
4 min read

Continuous glucose monitor may help reduce incidence of diabetic eye disease

Studies have shown that a reduction in HbA1c has a concomitant reduction in diabetic retinopathy.

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Diabetes is a growing health problem. As an ophthalmologist, I see it in my office. So does the CDC.

According to the CDC, “diabetes was the seventh leading cause of death in the U.S. in 2015.” More than 30 million Americans have been diagnosed with diabetes and an additional 80+ million are categorized as prediabetes, with the majority unaware of their illness. Left untreated, prediabetes can lead to type 2 diabetes, a complicated disease with major health ramifications including heart and kidney disease, stroke, vascular issues, vision loss and premature death.

As an ophthalmologist, I often advise patients to see an endocrinologist to rule out diabetes, although the diagnosis is often obvious, even at the incipient stage during a dilated eye exam and OCT.

For patients with diabetes, history has literally proven the Ben Franklin adage, “An ounce of prevention is worth a pound of cure.” For that reason, we strongly recommend all patients with diabetes, as well as those who have a family history of diabetes, be seen every 6 months.

Patients with diabetes need encouragement. It is not always easy to follow the regimented diet and exercise routines, and primary care physicians cannot carry the burden of reinforcement on their own.

As ophthalmologists, we do not shirk from this responsibility. We repeatedly remind our patients of the importance of keeping blood sugar and blood pressure under control, obtaining quarterly HbA1c testing and refraining from smoking.

We are keenly aware of the immense benefits of improved glycemic control in our patients with diabetes, reducing the occurrence of long-term microvascular complications including diabetic retinopathy, nephropathy and neuropathy. In the Diabetes Control and Complications Trial, intensive therapy reduced the risk for developing retinopathy by 76%. Similarly, in the United Kingdom Prospective Diabetes Study, every 1% decrease in HbA1c correlated with a 37% reduction in the risk for microvascular complications, including diabetic retinopathy.

These diabetes-related complications have staggering personal, societal and economic ramifications.

Interestingly, a topic that is rarely presented by ophthalmologists to patients with diabetes is the significant advantage of acquiring a continuous glucose monitor (CGM).

A CGM measures glucose levels in real time, 24/7, by employing a microsensor inserted under the skin that analyzes blood sugar levels every 5 minutes and wirelessly transmits the data to a monitor with a display, often to an app on a watch.

In a landmark 2008 study in the New England Journal of Medicine, the authors wrote:


“In patients 25 years of age or older, substantially tighter glycemic control was evident in the continuous-monitoring group in both glycated hemoglobin levels and sensor glucose results, without a significant increase in biochemical hypoglycemia. More patients in the continuous monitoring group than in the control group had a glycated hemoglobin level of less than 7.0% without having a severe hypoglycemic event.”

A plethora of subsequent studies has reinforced the findings of reduced HbA1c with concomitant reduction of diabetic retinopathy, nephropathy and neuropathy, while concurrently reducing the risk for hypoglycemia, whether the patient utilizes insulin injections or pump therapy.

The CGM will sound an alarm if the blood glucose is rising or dropping too quickly. Additionally, the alarm will serve to warn the patient if blood glucose reaches a predetermined low or high point. These alerts are beneficial during or after exercise or when the timing of meals or the type of food consumed is atypical.

In my practice, I have several hundred patients with diabetes. Anecdotally, those who acquire a CGM tend to improve or eliminate diabetic eye disease, lower their HbA1c and lose an average of 10 pounds. Soon after acquiring a CGM, snacking and eating desserts are substantially curtailed or eliminated because of instant feedback. Analogously, after witnessing the benefits from a brisk 30-minute walk or swim, patients tend to increase the frequency of exercise. They fervently believe, as do I, these devices have been a game changer in their health and overall welfare. So why are CGMs not readily accessible to all patients with diabetes?

It is all about dollars and lack of sense. Despite the annual outlay of $200 billion for diabetes and its related complications, in a short-sighted maneuver, insurance companies usually balk at covering CGMs.

Fortunately, help is on the way. An important study was published earlier this year in Diabetes Care, a journal of the American Diabetes Association. The researchers demonstrate that in addition to enhancing the quality of life for patients with diabetes, CGMs are also proven to be cost-effective when compared with daily use of test strips. The authors note that CGM costs are “well within thresholds normally used by insurance plans to cover medical devices.”

As physicians, we should promote this coverage and encourage our patients to consult with their endocrinologists about the appropriateness of a CGM for control of their diabetes.

While we may not be able to curtail the growth of diabetes in the U.S., we may at least reduce the risk for associated eye diseases.



Diabetes Control and Complications Trial Research Group, et al. N Engl J Med. 1993;doi:10.1056/NEJM199309303291401.

The Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group. N Engl J Med. 2008;doi:10.1056/NEJMoa0805017.

New CDC report: More than 100 million Americans have diabetes or prediabetes. Published July 18, 2017.

UK Prospective Diabetes Study Group. Lancet. 1998;doi:10.1016/S0140-6736(98)07019-6.

Wan W, et al. Diabetes Care. 2018;doi:10.2337/dc17-1821.


For more information:

Alan Mendelsohn, MD, FACS, can be reached at Eye Surgeons and Consultants, 4651 Sheridan St., Suite 100, Hollywood, FL 33021; email:; website:

Disclosure: Mendelsohn reports no relevant financial disclosures.