continuing education

Part II: Healthy Sight Counseling and Diabetes

An overview of diabetes and the eye for the eyecare professional

Background: Part I of this two-part series discussed diabetes and diabetic eye disease within the context of Healthy Sight Counseling (HSC). One of the most important aspects of HSC is its emphasis on preventive medicine.

Diabetes Type 2 is a potentially preventable disease in many individuals and the vision-threatening consequences of diabetic eye disease can be avoided or at least minimized in many cases with early diagnosis and treatment. For the eyecare professional practicing HSC, it, therefore, becomes crucial to identify individuals at high risk for developing diabetes and its ocular complications and to concentrate efforts on promoting Healthy Sight and Healthy Life.

Healthy Sight is in many ways dependent upon healthy eyes. While ocular disease can develop as a discrete entity, independent of systemic disease, there are many circumstances where unhealthy eyes develop as the result of an unhealthy body, so that Healthy Sight becomes a component of a Healthy Life. Recognizing this is essential for the successful implementation of HSC. There is perhaps no disease where the recognition of the connection between ocular and systemic disease is more crucial than in diabetes mellitus. And since diabetes—both ocular and systemic—is a treatable disease, and, in many cases, a potentially preventable disease, special attention should be focused on those populations at special risk for the development of diabetes.

DIABETES AND THE EYE—HSC AND POPULATIONS AT SPECIAL RISK

One of the most important aspects of HSC involves preventive medicine. With current constraints imposed by the already overburdened health care system, it is important to identify populations at increased risk for diabetes and its complications, so that efforts can be more effectively directed toward these specific populations.

Several risk areas for the development of diabetes may be targeted. These include hereditary factors, age, race/ethnicity, obesity, and lifestyle/habits (including sedentary lifestyle and smoking).

Hereditary Factors: There would appear to be a genetic predisposition to the development of juvenile diabetes type 1. This predisposition has been linked to a number of different HLA genes. HLA types DR3 and DR4 are associated with an increased risk for developing type 1 juvenile diabetes, while HLA-DR2 may protect from development of this disease. Familial aggregation has been documented in type 1 diabetes. The risk of an identical twin of a child with type 1 diabetes developing diabetes is about 35 percent, compared to only five to six percent for nonidentical siblings.

While there are multiple risk factors involved for type 2 diabetes and neither a distinct genetic defect or specific hereditary pattern has been convincingly described, there would appear to be some familial tendencies for the occurrence of this disease.

DIABETES AND AGE

The incidence of diabetes differs among different age groups. (See figure below.)

In the age group 18 to 79 years, the lowest incidence of diabetes overall was in the 18 to 44 years group (3.4 cases per 1,000 population). The highest incidence was in the 65 to 79 years group (13.1 cases per 1,000 population). Thus the incidence of diabetes type 2 and the risk for developing it increase with age among members of the adult population.

DIABETES IN CHILDREN

While the incidence of diabetes among adults increases with advancing age, the opposite end of the population curve is by no means unaffected by the current epidemic of diabetes. There are an estimated 178,000 American children with diabetes at this time.

Most cases of type 1 diabetes (75 percent) develop prior to age 18, with incidence peaks at ages 10 to 12 (major peak) and 5 to 7 (minor peak). There are multiple possible causes suggested for type 1 diabetes, including infectious (e.g., rubella and enteroviruses), environmental (e.g., cow's milk reactions), and immune-mediated (certain HLA types).

While type 1 diabetes still remains the predominant form of juvenile diabetes in the U.S. (representing about 90 percent of cases), and diabetes type 2 has been generally considered to be a disease of later life, a disturbing recent increase in the incidence of childhood diabetes type 2 is rapidly altering this demographic worldwide. For example, in Japan, type 2 diabetes is now more common than type 1 in the pediatric population.

This earlier time of onset for diabetes carries tremendous implications for Healthy Sight. The longer the duration of diabetes, the greater the chance for the development of diabetic retinopathy (DR), and the rate of progression of DR may be higher in younger than in older diabetics. In juvenile diabetes, retinopathy generally occurs after puberty, usually five to 10 years after diagnosis, although rarely it can be seen prepuberty after only one to two years of disease.

DIABETES AND RACE/ETHNICITY

Both the incidence and prevalence of diabetes are higher in certain racial/ethnic groups in the U.S. when compared to the general population. (See figure below.)

Below: Age-adjusted prevalence of diabetes, by race/ethnicity, in the United States

Overall rates are higher for African-Americans, American Indians, some Asian Americans, Native Hawaiians, and other Pacific Islander Americans, and in Hispanics/Latinos.

For example, non-Hispanic African-Americans are 1.8 times as likely to have diabetes as non-Hispanic whites of the same age. Approximately 3.2 million (13.3 percent of) non-Hispanic African-Americans have diabetes, and 18.2 percent of all non-Hispanic African-Americans over age 40 have diabetes.

The prevalence of diagnosed diabetes among non-Hispanic African-Americans is 1.6- to 1.8-fold higher than in whites, while the prevalence for both diagnosed and non-diagnosed diabetes is 2.3-fold higher.

Hispanic/Latino Americans are 1.7 times as likely to have diabetes as non-Hispanic whites of similar age. An estimated 2.5 million (9.5 percent of) Hispanic/Latino Americans ages 20 or older have diabetes.

Although data for Asian Americans is not as ready available as for Hispanic/Latinos and African-Americans, it would appear that diabetes is more prevalent in this group than among non-Hispanic whites. In data tabulated from the Behavioral Risk Factor Surveillance System (BRFSS), a population-based telephone survey of health status and healthy behaviors of some 150,000 persons, the body mass index (BMI)-adjusted prevalence of diabetes was found to be 60 percent higher in Asian Americans than in non-Hispanic whites.

There have been a number of reasons suggested to explain why diabetes should be more prevalent among certain minority populations. Limitation of access to health care is one; others include delay in diagnosis and treatment and suboptimal care.

In a number of studies, hemoglobin A1C levels, which are indicators of the adequacy of glycemic control and also predict the likelihood of development and progression of diabetic retinopathy, have been found to be consistently higher in non-Hispanic African-Americans compared to whites. Whether these differences are attributable to differences in diet, exercise, and rates of obesity, or whether there are some genetic factors that would make minority populations more susceptible to diabetes and its complications remains unclear.

DIABETES AND OBESITY

Obesity, as measured by BMI, is a major risk factor for diabetes. Obesity is a rising problem in the U.S. and worldwide. There are currently an estimated 44 million Americans who are classified as obese based on elevated BMI. This reflects a 74 percent increase compared to 1991 statistics.

This increase in obesity correlates with a 61 percent increase in the incidence of diabetes over that same time period. It has been projected that the risk for the development of type 2 diabetes increases by 7.37 times with a BMI greater than 40. (A healthy normal BMI ranges from 18.5 to 24.9.)

There is a definite link between the increased prevalence of type 2 diabetes in children and childhood obesity, with an estimated 10 to 15 percent of children in the U.S. classified as obese at this time (i.e., BMI in 85th percentile for age and sex, weight for height in 85th percentile, or weight 120 percent or higher of ideal for height).

DIABETES AND LIFESTYLE/HABITS

A sedentary lifestyle with lack of regular exercise has been identified as a risk factor for diabetes type 2. It is not clear whether it is the lifestyle pattern per se or the obesity, which is typically associated with diabetes, that is the problem.

The rising incidence of childhood obesity and, along with it, type 2 diabetes in the U.S., has been tied to the increasingly sedentary lifestyle of American youth—with more time spent on television, video games, and computers than physical activity and sports—and the dietary shift to high-calorie, carbohydrate-rich fast foods.

Smoking is another important risk factor for diabetes. Smoking can lead to increases in blood glucose levels. Smoking also increases the incidence of microvascular complications from diabetes and accelerates diabetes-related kidney and nerve damage.

Diabetic smokers are three times more likely to die from cardiovascular disease than age-matched diabetic non-smokers.

CONCLUSIONS

The health threat posed by diabetes to the eye and to the body is not likely to decrease any time soon; neither is the continuing rise in the prevalence of diabetes and in disease-related morbidity and mortality.

In fact, projections are that the number of cases of diabetes—and of the multitude of systemic and health problems it can lead to—will almost certainly increase with time. There is encouraging news on the horizon, however.

Our understanding of the pathophysiology of diabetes and the discovery of newer and better therapeutic options for treating it and dealing with its systemic and ocular complications continue to evolve.

Perhaps even more important is the increasing recognition that particularly with the more common type of diabetes, type 2, prevention may be possible and represents the best cure for many individuals.

Many aspects of the diagnosis and therapy of diabetes, along with the importance of maintenance and preventive medicine in dealing with its ocular and systemic complications, lend themselves well to the principles of Healthy Sight Counseling.

Since a large number of diabetics go unrecognized and ocular findings can represent the first clue to its diagnosis, the eyecare professional practicing HSC can play a pivotal role in identifying diabetes in the patient, even in that patient presenting for what is assumed to be routine vision care. This illustrates the importance of integrating vision with eyecare and doing away with the artificial separation often placed between the two.

In view of the strong correlation between the systemic and the ocular complications of diabetes—and the value of strict glycemic control in preventing, or at least in minimizing, them—the rationale for the relationship between systemic and ocular health that is stressed in HSC becomes clear, as does the value of the eyecare professional's establishing a therapeutic partnership with the health care professional in managing the diabetic patient.

Both quantity and quality of vision are concerns in the diabetic. Careful and regular follow-up can help to prevent diabetes-related quantity of vision loss in many diabetic patients, or at least to minimize its effects by recognizing disease and instituting appropriate therapy as early as possible.

Annual dilated eye exams are strongly recommended for all diabetics and for all individuals at high risk for diabetes.

Quality of vision concerns would appear to be even more of an issue in the diabetic than in the non-diabetic, with these individuals being potentially more susceptible to qualitative visual problems related to decreased contrast sensitivity, accentuation of glare, and photosensitivity. The judicious use of specific eyeglass lens materials, designs, and enhancements can help to successfully address these quality-of-vision problems.

The majority of diabetics eventually develop some degree of visual compromise related to their disease. Quality of vision becomes an even more relevant measure of visual comfort and satisfaction once quantity of vision has been adversely affected.

Since diabetics would appear to be more susceptible to indirect ocular complications of diabetes, including a higher risk for the development of cataract and AMD, and may also be more vulnerable to adverse effects of UVR exposure on their eyes, complete and consistent UVA and UVB protection, as offered by photochromic lenses, is a requirement in their eyewear.

Finally, HSC follows the medical model in emphasizing the invaluable role of preventive medicine—and preventive ophthalmology—in avoiding or at least in minimizing the impact of those diseases that affect the eye.

Since in many patients, under a variety of circumstances, diabetes type 2 may actually be a preventable disease, the practitioner practicing HSC must educate and counsel patients on:

■ The various risk factors for diabetes;

■ The need for regular eye examinations;

■ The role of the appropriate eyewear in enhancing quantity and quality of vision and in preventing or minimizing eye disease, and;

■ The value of establishing a therapeutic partnership between the eyecare professional, the health care professional, and the patient in effectively managing diabetes when it does occur in an attempt to avoid or at least to minimize its potentially devastating effects on the eye and the body.