Diabetic retinopathy remains the leading cause of new-onset blindness in populations of working age, even in the United States (21) and other industralized countres. Despite clearly defined clinical standards for evaluating and treating diabetic retinopathy cost-effectively, for a varety of reasons (see below), effective treatments such as laser surgery are underused. It has been estimated that 50% of adults with diabetes mellitus in the United States do not receive the recommended annual eye care that would allow diagnosis and treatment of diabetic retinopathy (38-41). Studies have also shown that many persons who require sight-preserving laser surgery do not receive it (42,43).
It has been reported that about 26% of patients with type 1 and 36% of those with type 2 diabetes mellitus have never had their eyes examined (44). These patients tend to be older, less educated and to have had a more recent diagnosis than those receiving regular eye care. They are also likely to live in rural areas and receive health care from a family or general practitioner. Alarmingly 32% of patients with diabetes mellitus at high rsk for vision loss never undergo an eye examination, and less than 40% of those with high-rsk characterstics for vision loss receive treatment (43,45). When examined, almost 61% of these patients are found to have diabetic retinopathy, cataract, glaucoma or another ocular maniestation of diabetes mellitus.
These findings have significant implications for the person and for society. It has been estimated that programmes to ideniiy and treat diabetic retinopathy would have saved the United States health care budget nearly US$ 400 million annually in the early 1990s (46), a figure that would probably be substantially higher today The total annual cost of diabetic eye disease in the United States at that time was almost US$ 2.8 billion, 75% of which was for persons who received treatment that was not proven to be effective (46). Even persons who are older at the onset of non-insulin-dependent diabetes can significantly benefit in years of sight saved by use of mydratic fundus photography for screening (47).
In order to prevent vision loss due to diabetic retinopathy, health care and eye care delivery systems in every society should be improved. While specific resources and methods differ widely from country to country, certain basic aspects of care must be delivered in all countres. By focusing on the patient and using common principles, a unified approach can be created, with respect for the resources and culture of each society, for best deliverrng eye care to patients with diabetes mellitus.
While the population prevalence of diabetes mellitus is over 6% in many high- and middle-income countres, a diagnostic 'test' with 98% sensitivity and 98% specificity would yield a post-test probability of a true positive (Bayes' theorem) of only 63% even i the prevalence were as high as 8%. Given the significant costs associated with testing every member of society and the costs for carng approprrately for false-positive patients, general population screening for diabetes mellitus with existing methods is considered neither approprate nor beneficial at present (48). I the prevalence in the population to be screened were significantly higher, however, screening would be approprrate. Once diabetes is diagnosed, screening for the complications of diabetes mellitus, such as diabetic retinopathy, is considered approprate and cost-effective (49).
4.1 Patients should know that they have diabetes mellitus and that the condition requires care
4.2 Patients should receive adequate care for diabetes mellitus
The only means of preventing diabetic retinopathy is by regulating blood sugar, blood pressure and other factors under the control of the patient, as guided by their prmary care provider or endocrmologist. Studies in the United States have shown, however, that physicians do not care for patients with diabetes in the manner indicated by the results of randomized controlled trals as embodied in guidelines from their professional societies, the Agency for Healthcare Research and Quality and other organizations (38-41). McGlynn et al. (39) found that a typical patient with diabetes mellitus in the United States would receive only about 40% of the recommended care in a given year.
4.3 Patients should undergo eye evaluation for the presence of diabetic retinopathy
Al professional eye care organizations advocate annual eye examinations for patients with diabetes and prompt treatment when indicated, in order to achieve the pubic health goal of minimizing vision loss (50-52). Some organizations recommend examinations every other year for persons under excellent glycaemic control and no retinopathy on a previous examination. The importance of perodic eye examinations is reflected in their inclusion as a quality indicator for health pans used in the United States (38,41).
Nevertheless, studies have shown repeatedly that patients with diabetes are not evaluated or treated in a timely fashion. For example, an analysis of self-reported care by the civilian, non-institutionalized population of the United States revealed that less than 50% of patients with diabetes and only 60% of high-rsk patients (with previous retinopathy or long duration of diabetes) had undergone a dilated eye examination in 1989 (38). Other studies have shown that, although screening and blindness prevention programmes can increase the rate of examinations of the dilated eye, many persons still would not have an eye examination (53,54).
In a study of patients with chronic diseases throughout the United States, McGlynn et al. (39) found that the rate of eye examination remained at 5060% after more than 10 years of concerted effort, and that the rate was as low as 19% i chart documentation of a dilated eye examination was required as the gold standard. In a longitudinal analysis of care over 5 years derved from Medicare administrative claims (and not chart documentation), Lee et al. (55) found that less than hal of patients with diagnosed proliierative retinopathy (and less than one-fourth of persons with background retinopathy at the first visit) had undergone at least one examination every 15 months over 5 years, suggesting that the longitudinal pattern of care use is problematic. To the extent that the findings of McGlynn et al. can be extrapolated, this suggests that less than 20% of patients with proliierative retinopathy at the index visit have undergone at least four spaced examinations of the dilated eye over 5 years.
The first problem is therefore to ensure that patients who are already known to have diabetes (over 98% of whom visit their prmary care physician or endocrmologist at least once a year) receive an examination of their eyes and retinas. Understanding the barrers to receiving examinations is one part of the equation; ultimately the issues that contrbute to preventable blindness among persons with diabetes mellitus must be identified and addressed. Because of the importance of this issue, the consultation addressed approaches that would improve the efficiency and performance of retinal assessment among patients with known diabetes mellitus.
4.4 If retinopathy is detected or if a patent is referred to an eye care provider for an examination, the society must deliver the necessary level of eye care
The question of what management should be provided once a given degree of diabetic retinopathy is detected is up to each society. A critical element of delivering eye care for patients with diabetes is the availability of trained personnel to provide care, ranging from examination to surgical intervention. In developed countries, there is one ophthalmologist per 15 000-50 000 population (56). When optometrists are included, the ratio fa Is to as low as one per 6000 population (private communication from the American Academy of Ophthalmology). In these countries, therefore, the availability of providers of eye care for patients with diabetes is not an issue. Whether this situation will continue is unclear, given the ageing of the populations of developed countries and the growing use of health care services as economies continue to grow (57). The issue of adequate human resources therefore might not be limited to less developed countries in the future, perhaps providing opportunities to design innovative methods of delivering care.
In developing countries, there are not enough eye care providers to give even basic eye care to their populations, let alone to patients with diabetes. WHO has estimated that even in countries with rapid economic development, such as China and India, the ratio is one provider per 80 000 or more population, although some metropolitan areas (e.g. Hong Kong, Special Administrative Region, People's Republic of China) have ratios similar to those of developed countries.
As the populations of these countries and their economies continue to grow, there will be greater pressure on the available eye care to prevent or treat other causes of visual impairment, such as cataracts (57). The second challenge is thus to find other personnel or other examination techniques that can be used in locations where trained professionals, especially ophthalmologists, are not available or where their skills can be used more productively for resolving other problems, such as reducing blindness due to cataract. Further questions are whether the alternative personnel or techniques should be able to detect a certain degree of diabetic retinopathy (screening) or whether they should be capable of accurate staging or classification in order to determine when and what treatment is needed; and whether the alternative personnel should provide treatment i ophthalmologists are not available.
4.5 Patients should be sufficiently aware and motivated that they not only undergo an eye examination but also return regularly for such examinations
'Patient awareness' or 'patient education' can more usefully be expressed as 'What is the patient buying?' with respect to eye examinations to detect diabetic retinopathy. Diabetes is a chronic disease for which there is currently no cure and which requires constant care and attention. Patients with diabetes can be thought of as 'buying' information about their disease and their eye status well before they 'buy' the treatment necessary for sight-threatening retinopathy Thus, it is not merely a question of providing enough information in a form that patients can understand—the traditional approach—but of 'marketing' the value of eye care examinations and, if necessary treatment.
Discussions in focus groups of patients with diabetes mellitus (sighted and bind), their support systems and all types of care providers have raised a number of issues (58,59), apart from the information important for doctor-patient communication. Problems of literacy, numeracy and difficulty in reading were raised in respect of the available educational materials, and the need for culturally appropriate materials and examples was mentioned. A third finding was that patients learn (and doctors communicate) in some ways (e.g. visual, aural, interactive, touch) better than others. These findings emphasize the importance of understanding perceptions in increasing the use of eye care services by patients with diabetes mellitus (60).
Communications destined for patients can have negative or positive messages, and the effect might be different from that intended or anticipated. For example, in some patients, use of the negative message 'You will lose your sight i you don't take care of your diabetes.' only reinforced their fatalistic belief that they were going to go bind, and they concluded that there was nothing they could do. Similarly, patients often behave to their families, friends and doctors in ways that they know are detrimental to their health in order to establish their independence from 'overbearing' control. Another key point was the contrast between the message of the patient's primary care physician ('You will lose your sight i you don't control your sugar.') and that of the ophthalmologist ('You're fine. Come back in a year') (58). The conclusion of many patients that their eyes were healthy even when they had poor glycaemic and blood pressure control led them to question the skill and knowledge of their primary care provider, thus reducing their confidence.
While there are several beneficial methods of patient education, published studies have demonstrated a lack of persistent behavioural change in patients. Educational materials and campaigns directed to patients with diabetes should therefore be reorented to address issues from their perspective and not solely that of the provider (60). Direct, one-on-one interactions with tangible feedback are those in which a 'marketing' approach is most likely to be effective. Providers and organizations should thus reassess their educational campaigns and redesign them into marketing campaigns.
The importance of orenting educational messages to each culture and society and to each group within each society is aptly demonstrated in the success of educational and outreach programmes conducted in varous countries. Key steps descrbed to the consultation included:
■ involvement of local populations in the local health care infrastructure;
■ adaptation of the message to fit the needs and expectations of the target audience; and
■ use of different modes of communication to reach as many different 'market segments' as possible.
5. PRINCIPLES FOR ORGANIZING EYE HEALTH SYSTEM FOR THE CARE OF DIABETIC RETINOPATHY
Having agreed upon the steps necessary for delivering eye care to prevent blindness and vision loss due to diabetes mellitus, the consultation sought to identify the basic prmciples of a care system that would be applicable across many settings, so that insights and lessons from diferent areas could be shared to make individual programmes more effective.
First, each society should determine whether sufficient resources can be devoted to treatment of diabetic retinopathy if it is detected. As treatment requires trained operators and relatively sophisticated equipment and care environments, competing priorities might make treatment unaffordable. If a disease cannot be treated, the benefits of detection are more limited. Thus, those societies and cultures in which treatment of diabetic retinopathy (or even diabetes mellitus) is less cost-effective than other interventions have a more limited rationale for detecting the condition. The rationale would stress the value of educating patients about the presence of non-sight-threatening retinopathy in order to encourage them to adopt better blood pressure and glycaemic control to reduce the progression of retinopathy and other microvascular complications of diabetes mellitus.
Second, if a social decision is made to treat detected diabetic retinopathy, a patient-centred approach within a public health context could yield optimal results. Once a decision is made to detect eye disease in patents with diabetes and to treat it i it is found, the success of the programme will depend on patent-centred marketing, to convince patients to return for regular eye examinations and treatment. By adopting a patient perspective, pubic health systems and campaigns can be designed that will be more effective in maintaining a desired behaviour over time. At the same time, the pubic health context will maxmize the use of social resources. It will also allow application of effective methods for reaching patients and delivering care that are derived from other, successful programmes, even i they are not based on a western medical model. By broadening ideas for provdng eye examinations and appropriate treatment for diabetic retinopathy, many more patients could be served than by relying on care delivered only by ophthalmologists in societies where their time and skis might be better used in other endeavours or programmes.
Third, there is always a trade-off between performance and costs. For example, while seven-field stereo-photographs of the retina read by a trained observer at a dedicated reading centre or examination by an experenced professional specialized in diabetic retinopathy are the ideal 'gold standards', these systems can be very expensive in terms of social resources. In contrast, examination of an undilated eye with a direct ophthalmoscope by a non-physician health care worker might result in failure to detect a number of cases of diabetic retinopathy, although it is likely to be the least expensive method. No country can escape making tradeoffs between resource use and system performance in arriving at key decisions. Even determining the frequency of follow-up screenings for diabetic retinopathy can vary on the bass of what is considered to be an acceptable rate of otherwise preventable vision loss.
Fourth, the decisions made by each country are unique to that country, its resources, its social expectations and the existence of an appropriate health care infrastructure. Givrng information on the performance of different techniques for detecting diabetic retinopathy to the responsible entities in each country will allow them to make the decisions and trade-offs that best suit their conditions, albeit in the context of common principies, patient-centred care and pubic health. Use of standardized definitions of retinopathy evaluation and the assessment of costs and performance will enable countres to learn from each other's experence.
To assist countres in making informed decisions about whether and how to screen for diabetic retinopathy and how to manage the care of patents who need examination or treatment by trained eye or health care professionals, the consultation highlighted key issues and examined certain issues in depth. A review of the literature indicated that the most important varables were: the accuracy of different methods (and types of observers) for detectng the presence or severity of diabetic retinopathy; the locations can best serve patent needs; and the interval between eye screenings or examinations.
It would seem obvious that accurate assessment of the presence or absence of retinopathy and the degree of severity are vital to prescrbing approprate care to prevent the onset of vsion loss and blindness. Yet, two studies in the United States over 20 years ago showed that this was not a safe assumption. Sussman et al. (61) identiied varations in the ability of physicians to diagnose eye disease in patents with diabetes accurately. While retina specialists missed no cases of prolierative diabetic retinopathy internists, diabetologists and medical residents missed 49% of such cases. The overall error rate in classifying severity with the system of the Diabetic Retinopathy Study was 61%, and that of general ophthalmologists was 48%. Kleinstein et al. (62) reported that optometrsts could correctly decide i retinopathy was present in 77% of eyes, with correct staging in 57% (error rate, 43%).
More recent work indicates that performance levels are not yet adequate. Schmid et al. (63) found that optometrsts in Australia detected retinopathy in 94% of eyes, but the severity classiication was accurate in only 58%. Prasad et al. (64) found that optometrsts in the United Kingdom were able to identify sight-threatening diabetic retinopathy on screening in 76% of cases. In numerous studies of photographic and telemedicine systems, the performance of general ophthalmologists in detecting retinopathy and staging the severity of disease generally fell short of that of camera-based systems (65). It should be noted, however, that in most studies the performance of eye care providers in determining whether retinopathy was present and, to a lesser extent, its grading into sight-threatening or more severe retinopathy was signiicantly more accurate than that of provders asked to grade severity into four or more classes, as in the Diabetic Retinopathy and Early Treatment Diabetic Retinopathy studies.
Use of non-ophthalmic physicians and other health care providers in eye care for patients with diabetes has been suggested by a number of authorities. Ophthalmologists generally constitute no more than 2% of the physician workforce, even in developed countres, and are particularly scarce in some regions of the word. Thus, additional manpower is needed to provide care not only for patients with diabetes but also for those with other eye diseases, such as cataract. Patients with diabetes have identiied lack of care coordination as a major barrer to receiving regular eye care:
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