Cummings and Cunha-Vaz Table 1 WHO classiﬁcation of diabetes mellitus (WHO 1999) *Fasting venous plasma 7.0 mmol/L *Random venous plasma 11.1 mmol/L Type 1 (beta-cell destruction, usually absolute insulin deﬁciency) 1A Autoimmune 1B Idiopathic Type 2 (range from predominant insulin resistance to predominantly secretory defect ± insulin resistance) Other speciﬁc types Genetic defects of beta cell function or insulin action Diseases of the exocrine pancreas Endocrinopathies Drug/chemical induced Infections Rare immune-mediated forms Other genetic disorders associated with diabetes Gestational diabetes *One abnormal blood glucose measurement is sufﬁcient in the presence of symptoms, but for the asymptomatic person at least one additional plasma/blood glucose test result with a value in the diabetic range is essential. Worryingly, the incidence of pediatric type 2 diabetes is rising and, exceeds 4% in American Indians aged between 15–19 years (Dabelea et al 1998). The asymptomatic nature of this condition, common until complications emerge, increases the burden of diabetes as, for example, up to one third of patients may have retinopathy at diagnosis. There is a resultant need for more widespread, efﬁcient screening to enable earlier capture of new cases, but there is no universal agreement as to how this can be best achieved. In contrast to type 2 diabetes, the relatively abrupt onset of type 1 diabetes usually negates the likelihood of diabetic complications at diagnosis (less than 2% of patients have retinopathy at presentation). It is estimated that 10–20 million individuals suffer from this condition globally (Rewers et al 1988). Type 1 diabetes peaks in patients under the age of 15 years (with prevalence of up to 0.3%) and has dramatic geographic variability. A child in Finland, for example, is 400 times more likely to develop type 1 diabetes than a child in China (Steck et al 2004). The burden of diabetes The implications of diabetes are immense at an individual, caregiver and societal level. When considering some of the potential burdens faced by individuals with diabetes, as sum- marized in Table 2, it is not surprising that these patients are prone to states of depression and anxiety (Gavard et al 1993). The Costs of Diabetes in Europe-2 (CODE-2) Study (Baxter et al 2000) and T2ARDIS Study (GSK 2000) 370 perhaps provide the most robust data on the economic burden associated with diabetes across Europe. These studies have identiﬁed that the healthcare costs associated with patients with diabetes are more than twice those of age-matched individuals without diabetes. Using a UK-based model, this lifetime cost equates to £33,000 for male patients and £43,000 for female patients, compared with £15,000 for men and £22,000 for women without diabetes (Bagust et al 2001). CODE-2 also demonstrated that the costs of those patients with microvascular complications, such as retinopathy, are nearly twice those associated with patients without complica- tions. These calculations underestimate the true cost burden associated with diabetes as they fail to take into account absence from work, early retirement or premature death due to the condition. Evidence from studies in both type 1 (DCCT 1996) and type 2 (UKPDS 2000) diabetes suggest that better glycemic control is cost-effective in reducing diabetes-associated morbidity and mortality. Systematic screening for diabetic complications such as retinopathy has also been shown to be a cost-effective intervention (James et al 2000). The pathogenesis of diabetes Type 1 process Type 1 diabetes indicates the presence of underlying pancre- atic beta-cell destruction with a progressive decline in insulin production and secretion. Exogenous insulin administra- tion is required for survival to prevent the development of Table 2 Examples of the individual burden of diabetes Lifestyle Dietary, exercise, and changes to other factors associated with diabetes Monitoring and management of diabetes Restrictions for sports and other leisure activities Vehicle driving limitations Work Clinical Financial Restrictions on occupations Implications at work for monitoring/managing diabetes Need for regular health checks/blood tests The development (or fear of development) of diabetic complications and their implications Greater likelihood of hospital admission Often the need for regular medication with risks of side effects Increased risk of other conditions associated with diabetes Costs of treatment (in non-state health subsidized societies) Loading of health-related insurances Loss of income through diabetes-related illness Clinical Ophthalmology 2008:2(2)