Diabetic Retinopathy Management

THE SCOPE OF THE PROBLEM OF THE EPIDEMIC OF DIABETES

In 1997, Amos1 estimated that 124 million people worldwide have diabetes, 97% non-insulin-dependent diabetes mellitus (NIDDM), and that by 2010 the total number with diabetes is projected to reach 221 million. The regions with the greatest potential increases are Asia and Africa, where diabetes rates could rise to 2 or 3 times those experienced in 1997. In 2000, Sorensen2 reported that the World Health Organization has recognized that there is a ‘global epidemic of obesity’ and the prevalence of type 2 diabetes is rising in parallel. The International Diabetes Federation have estimated the prevalence of diabetes in 2003 in the 20–79 age groups and projected this to an estimate in 2025. This is shown in Fig. 1.

North America

Reports from the USA and Canada have shown the following rises. 1 In 2000, Burrows3 reported that the number of native Americans and Alaska natives with diagnosed diabetes increased by 29% from 43,262 to 64,474 individuals between 1990 and 1997. By 1997, the prevalence was 5.4%, and the age-adjusted prevalence was 8.0%. 2 In 2000, Mokdad4,5 reported the results of the Behavioral Risk Factor Surveillance System in the USA 1990–98. The prevalence of diabetes rose from 4.9% in 1990 to 6.5% in 1998 and to 6.9% in 1999. The prevalence of diabetes was highly correlated with the prevalence of obesity (r = 0.64, p < 0.001). 3 In 2001, Boyle6 estimated that the number of Americans with diagnosed diabetes is projected to increase 165%, from 11 million in 2000 (prevalence of 4.0%) to 29 million in 2050 (prevalence of 7.2%). 4 In 2007, Lipscombe7 reported the prevalence of diabetes in Ontario, Canada to have increased substantially during the past 10 years, and by 2005 to have already exceeded the global rate that was predicted for 2030. Using population-based data from the province of Ontario, Canada, age-adjusted and sex-adjusted diabetes prevalence increased from 5.2% of the population in 1995 to 6.9% in 2000 and to 8.8% of the population in 2005.

The UK

Reports from the UK have shown the following rises. 1 In 2000, Ehtisham8 reported type 2 diabetes emerging in UK children. 2 In 2001, Farouhi9 constructed an epidemiological model by applying age-, sex-, and ethnic-specific prevalence rates to resident populations of England at national, regional and PCT level. The estimated prevalence of total diabetes for all people in England was 4.41% in 2001 equating to 2.168 million people. Type 2 92.3% and type 1 7.7% (166,000 people). 3 In 2002, Feltbower10 reported an increasing incidence of type 1 diabetes in south Asians in Bradford. 4 In 2006, the latest data11 in England for people diagnosed with diabetes have shown a national prevalence of diabetes of 3.35%. 5 In 2007, Evans12 reported that a diabetes clinical information system in Tayside, Scotland, showed a doubling in incidence and prevalence of type 2 diabetes between 1993 and 2004, with statistically significant increasing trends of 6.3 and 6.7% per year respectively.

Worldwide reports 

In 2000, Sidibe13reported that the rise in complications of diabetes mellitus in Africa has gone hand in hand with the growing disease prevalence. 2 In 2001, Zimmet14 reviewed the global and societal implications of the diabetes epidemic.

ADVANCES IN THE MANAGEMENT OF DIABETES

Advances in management of diabetes have had a substantial impact on DR. These are discussed in detail in Chapter 2. The demonstration by the Diabetes Control and Complications Trial39 that retinopathy in type 1 diabetes could be reduced by intensive treatment of blood glucose has led to much better control and retinopathy progression has been reduced. Studies40,41 in the early 1990s showed the link between hypertension in type 1 diabetes and a higher occurrence of retinopathy and progression of pre-existing retinopathy. A similar demonstration in the United Kingdom Prospective Diabetes Study42 (UKPDS) that in type 2 diabetes the development of retinopathy (incidence) was strongly associated with baseline glycaemia and glycaemic exposure and that progression was associated with hyperglycaemia (as evidenced by a higher HbA1c) has led to better control in type 2 diabetes and in reduction in retinopathy progression. The UKPDS43 also demonstrated that high blood pressure is detrimental to every aspect of DR in type 2 diabetes and that a tight blood pressure control policy reduces the risk of clinical complications from diabetic eye disease (see Fig. 3).

ADVANCES IN THE MANAGEMENT OF DIABETIC RETINOPATHY

Since Spalter44 described the photocoagulation of circinate maculopathy in DR, clear evidence for the efficacy of laser treatment for diabetic eye disease has been shown from the Diabetic Retinopathy Study45–49 and the Early Treatment Diabetic Retinopathy Study50–58. In 1981 they reported47 that photocoagulation, as used in the study, reduced the 2-year risk of severe visual loss by 50% or more (see Fig. 4). In 1985, a report50 from the Early Treatment Diabetic Retinopathy Study showed that focal photocoagulation of ‘clinically significant’ diabetic macular oedema (CSMO) substantially reduced the risk of visual loss. Smiddy59 wrote an excellent review in 1999 when he noted that, according to the Early Treatment Diabetic Retinopathy Study, at least 5% of eyes receiving optimal medical treatment will still have progressive retinopathy that requires laser treatment and pars plana vitrectomy. He also noted that, although vitrectomy improves the prognosis for a favourable visual outcome, preventive measures, such as improved control of glucose levels and timely application of panretinal photocoagulation, are equally important in the management. Vitrectomy clearly does have a place in the management of diabetic eye disease (Fig. 5). Evidence of improving visual results during the last 20 years following vitrectomy has been shown in studies reported by Blankenship,60 Thompson,61–64 Sigurdsson,65 Flynn,66 Nakazawa67, Karel,68 Harbour.