By diabetes mellitus you may understand sugar diabetes – but this is only partly correct.
Diabetes is certainly related to sugar metabolism, but elevated blood glucose levels are only a symptom, not the (sole) cause of diabetes, as was long believed. Because even a perfect blood sugar level cannot prevent the progression of diabetes. Certainly, the adjustment of blood sugar and blood pressure as well as, especially in type 2 (adult-onset diabetes), body weight play a major role. These factors influence the progression of the disease and can be treated. Hereditary disposition and lifestyle habits such as diet, nicotine and alcohol consumption, and fat metabolism are much more difficult to influence. The disease is probably caused either – similar to rheumatic diseases – by a regulatory disorder of the immune system with damage to the pancreas (type 1, juvenile diabetes) or by a reduced sensitivity of the body cells to insulin (type 2).
GENERAL, EXPLANATION OF TERMS
After age-related macular degeneration, eye involvement in diabetes (diabetic retinopathy) is the second leading cause of visual impairment in Europe and North America. It is the leading cause of blindness in the 20 to 70 age group. In Germany, diabetes is the most common metabolic disease affecting more than 4.5 million people. In Switzerland, the incidence is estimated to be at least 4.9% in men and 3.7% in women (about 350,000 people). From the fortieth year of age onwards, the incidence of diabetes increases up to 16% in men and 12% in women between 75 and 84 years of age. Between 1995 and 2008, in parallel with an increase in the incidence of overweight people, diabetes increased significantly, particularly among men. In the meantime, type 2 diabetes has developed into a worldwide epidemic and today causes costs amounting to 4% of total health care costs (FOPH estimate 2012). Changes in the eyes (especially in the retina) are already found in almost 18% of type 2 diabetics at the time of diagnosis. Good vision is often mistakenly equated with a healthy retina that does not require treatment. Visual disturbances are a late symptom, which is only observed after several years if the disease has progressed and no retinal treatment is available. The most frequent cause of visual disturbances in diabetes is a swelling of the retinal center (macular edema), which occurs less frequently in type 1 diabetes around ⅓ than in type 2, whereby one eye is affected in 55% and both eyes in 45%.
Advanced diabetic retinal damage, B = bleeding, E = protein deposition, L = laser focus, S = optic nerve, G = vessels, M = macula: site of sharpest vision
More and more we understand the interrelationships of individual factors for the progression of the disease, which can therefore be better and better treated. Particularly in the treatment of damage to larger vessels, major advances have been made in the last 10 to 15 years, which have significantly reduced cardiovascular risks and complications. As a consequence of the increasing average age of the population, the number of diabetics will continue to rise. More and more diabetics will reach diabetes stages in which the progressive damage of small vessels (microangiopathy) is the main symptom. This is particularly evident in the kidneys (nephropathy), the nerves (neuropathy) and the retina.
Causes and consequences of the diabetic metabolic disease
Since the 1980s, laser therapy has been the core element in the treatment of diabetic retinal changes. Its effect is attributed to an improved oxygen supply in the retinal areas with a better blood supply after laser treatment of retinas without blood supply. Although laser therapy rarely leads to an improvement in function, in the long term it significantly reduces the risk of severe vision loss. In the future, more gentle newer laser procedures will presumably enable even greater effects with less tissue damage.
In the past, a vision disorder caused by diabetes could only be treated if it involved bleeding into the inside of the eye (the vitreous body). As soon as damage to the center of the retina was discovered as the cause, nothing more could be done except to improve blood sugar and blood pressure control, which is why over 20% of late-stage diabetics went largely blind. For almost 15 years now, medication has been administered into the vitreous cavity. Although this very expensive treatment is only effective for a short period (1 to 3 months), it can be repeated if necessary and leads to a rapid recovery of visual acuity and temporary stabilization of the retina until long-term stability of laser vision and better diabetes control is achieved. However, this often takes more than a year. Newer drug treatments aimed at influencing the basic problem at the supporting and nutritional cells of the blood vessels are currently undergoing clinical testing. They appear to reduce the risk of severe visual impairment and the need for laser therapy but cannot stop the progression of diabetic retinopathy. Surgical procedures, in particular vitrectomy (removal of the vitreous body), are thus used much less frequently, and usually only when drug options have been exhausted. The treatment of the consequences of the diabetic metabolic disorder and the resulting vascular damage in the entire body with strict regulation of blood sugar and blood pressure and control of fat metabolism is clearly in the foreground for long-term preservation of visual function and quality of life. A high blood sugar level, but above all strong fluctuations in the blood sugar level, have a long-term effect on the small retinal vessels. High blood pressure that is not sufficiently reduced accelerates the progression of diabetic eye changes, especially the transition to an aggressive form. For this reason, every patient with diabetes mellitus should have ophthalmological care, even if there are no complaints or symptoms from the eyes. Laser treatment of diabetic retinal changes should be started when the blood circulation in the retina shows disturbance, and before a visual impairment occurs.