Eye care an important part of diabetes management

Issue: December 1997

ByKari Blaho, PhD

Diabetes mellitus (DM) is caused by a relative or absolute lack of functional insulin. There are two types of DM: insulin dependent, also known as type 1 or juvenile-onset DM, and insulin-independent, also known as type 2 or adult-onset DM. Adult-onset DM is caused by a relative loss of insulin or insulin function, while juvenile-onset DM is usually caused by loss of the pancreatic cells that secrete insulin (ß-cells).

Type 1 diabetes usually presents between the ages of 11 and 15 years. Type 2, or adult-onset, DM usually presents in middle age (51 to 55 years), is more likely to occur in women who are obese and can be controlled by weight loss, diet and exercise with or without insulin therapy. Insulin is always part of treating type 1 DM.

Ocular signs of diabetes

One of the long-term complications of diabetes is retinopathy leading to blindness. It is estimated that more than 80% of patients with DM for longer than 20 years will have some degree of retinopathy. Early on, support cells (pericytes) in the basement membranes of the retinal vasculature are lost, leading to increased vascular permeability and focal anoxia.

Vascular damage from hyperglycemia is hypothesized to be a result of two possible mechanisms: the nitric oxide synthetase pathway and the polyol pathway. Retinal hemorrhages and hard exudates are a result of the increased vascular permeability. New vessels appear on the surface of the retina or optic disk, giving the retinopathy a proliferative appearance.

Microvascular changes in the eye often will mirror vascular changes in the renal and cardiac vasculature. Results from several clinical trials have correlated an increased risk of proliferative retinopathy with hemoglobin A1C (HA1C) values of greater than 8.1%. HA1C is a measure of glycosylated hemoglobin, which essentially reflects the average glycemic control for several weeks prior to the test.

Other common ocular findings in diabetes include fluctuations in visual acuity secondary to changes in lens hydration from changes in blood glucose. Diabetic patients are also more prone to cataracts and ocular infections.

Treating diabetes

The treatment of diabetes, independent of type, should include a controlled diet and exercise. There are two types of glycemic control: traditional control and tight control. In addition to diet and exercise, traditional glycemic control includes checking blood glucose one to three times per day.

The main goal of traditional control is to keep the patient out of ketoacidosis. Intermediate- and short-acting insulin are administered two to three times per day. The patients' regimented diet, activity and exercise revolve around the insulin schedule. Traditional control is usually reserved for patients not capable of, or unwilling to undertake the tight control regimen.

Tight control is a newer approach to glycemic control. Fasting blood glucose is maintained at less than 90 to 100 mg/dL, random blood glucose is maintained at less than 150 mg/dL and hemoglobin A1C is maintained at less than 7% to 8%. Blood glucose is monitored three to five times per day with each meal. Long-acting insulin is administered in the morning, and regular insulin is administered on a sliding scale.

Tight control is appropriate for highly motivated patients who are capable of adjusting their own insulin, who will perform frequent checks and injections and who are educated to recognize hypoglycemia. In essence, tight control requires the patient to play a major role in treating their diabetes. Tight control offers several advantages over traditional control. It allows more physiologic control of electrolytes and lipids, delays and slows the progression of the long-term complications of diabetes, such as vascular disease (including eye disease), and allows for more freedom in scheduling of meals, exercise and travel.

Insulin: drug of choice

Insulin, in its various forms, is the drug of choice for treatment of both types of DM. However, for type 2 DM, the oral hypoglycemic agents can increase the sensitivity of insulin for its receptor and increase insulin release from ß-cells in the pancreas. One of the most common side effects of the DM treatment is hypoglycemia.

Regardless of the treatment regimen, all health care providers can assist in the treatment of diabetes. It is estimated that 700,000 patients with diabetes are at risk for vision loss from proliferative retinopathy or macular edema. Therefore, regular eye care is especially important for diabetic patients, and the optometrist can make use of regular visits to reinforce the importance of glycemic control, reassure patients and answer any questions concerning their medications or vision.

Regular eye exams also afford the opportunity for early identification of the diabetic who is experiencing complications such as depression, lack of glycemic control and early microvascular disease. Some studies have shown that retinopathy associated with diabetes is significantly worse in patients with a history of depression associated with the disease.

Be prepared for hypoglycemia

Some considerations should be made for diabetic patients in the office setting. These patients are on a fairly rigid schedule and cannot wait for meals or medicines. It is best to schedule diabetics for early morning appointments. If you anticipate that you will be delayed in seeing them, tell them at the time they make an appointment to bring a snack or their medications.

Be prepared to recognize and manage episodes of hypoglycemia, as illustrated by the following case:

A 44-year-old woman with known diabetes was found unresponsive and slumped in a chair by a receptionist. She had been waiting for an hour and a half to be seen for her regular eye exam. Her vital signs were normal, and after several attempts to wake her, the paramedics were called. On arrival, they began an IV and administered D50 (dextrose, 1 amp). After approximately 1 minute, the patient opened her eyes and asked what happened. She was now alert and oriented and left the office unassisted.

Many new-onset diabetics may present with diabetic ketoacidosis, so it is a good idea to keep in mind the clinical findings that commonly present in patients and to remember that this condition can be life-threatening.

New-onset diabetes described

A 34-year-old obese woman was referred urgently to our emergency department by a local optometrist. The patient had presented to the OD with a chief complaint of blurry vision for the past 10 days or so. A history and physical exam performed by the optometrist revealed that the patient was drinking two to three pitchers of water at a sitting, had lost 20 pounds in the past month and for the past 2 days had several incidents of nausea and vomiting. There was a positive family history of diabetes.

Suspecting new-onset diabetes, the optometrist performed an in-office blood glucose, which was off the scale (too high to read). The patient was referred urgently to the emergency department. There, the patient also complained of malaise, continuous blurry vision, abdominal pain and thirst. Vital signs were as follows: blood pressure 140/100 mm Hg, heart rate 112 beats/minute, respirations 22/minute and temperature of 97.7°F. Laboratory values revealed a blood glucose of 1,066 mg/dL, pH of 7.28 and bicarbonate of 22. Urinalysis showed glucose, ketones and proteinuria.

She was admitted to the hospital and started on insulin therapy and diabetic education. After 3 days her vision cleared, as did her other symptoms. She was discharged in good condition with follow-up scheduled for eye care and primary care the following week.

For Your Information:

Kari Blaho, PhD, is research director, Department of Emergency Medicine and Clinical Toxicology, UT Medical Group, 842 Jefferson Ave., Suite A-645, Memphis, TN 38103; (901) 545-8699; fax: (901) 545-8996. Dr. Blaho has no direct financial interest in any of the products mentioned in this article, nor is she a paid consultant for any company mentioned.

References

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Cohen T, Welch G, Jacobson AM, de Groot M, Samson J. The association of psychiatric illness and increased prevalence of retinopathy in patients with type 1 diabetes mellitus. Psychosomatics. In press.

Lewis EJ, Hunsicker LG, Bain RP, Rohde RD. The effect of angiotensin converting enzyme inhibition on diabetic nephropathy. N Engl J Med. 1993;329:1456-1462.

Lustman PJ, Griffith LS, Clouse RE, Cryer PK. Psychiatric illness in diabetes mellitus: relationship to symptoms and glucose control. J Nerv Ment Dis. 1986;174:736-742.

Warram JH, Manson JE, Krolewski AS. Glycosylated hemoglobin and the risk of retinopathy in insulin-dependent diabetes mellitus. N Engl J Med. 1995;332:1305-1306.