Diabetes
Diabetes mellitus has two main types: insulin-dependent Diabetes mellitus (Type I) and non-insulin-dependent diabetes mellitus (Type II). Approximately 3% of the population has diabetes mellitus and the majority of the patients (approximately 90%) have type II diabetes. A high level of blood glucose is present in both types. Insulin hormone is produced by the abdominal salivary gland (Pancreas) to reduce blood glucose. Sufficient amounts of insulin are not produced in type I diabetes patients. Whereas, in type II diabetes patients, there is disruption in the efficiency of present insulin. Type I diabetes is usually observed in children and young adults. Type II diabetes is usually observed in individuals with advanced age or excessive weight. Increasing blood glucose value damages the cells in the vessel walls in organs. For the eye, the retina and iris are particularly affected. The vessel walls in the retinal capillaries lose supportive cells. Small ruptures occur in the vessel wall (microaneurism), which lead to leakage. Thus, blood, fat and water leakages may reach the retina through the cappillaries. In addition, increased blood glucose may thicken the cells which constitute the cappillaries (endocytes). Therefore, the vessels are obstructed and the retina can not be nourished with sufficient oxygen. The reaction of the eye in response is to form new vessels with connective tissue (neovascularization). Most of the time, blood flows into the cornea through these vessels (Cornea bleeding, see the picture below).
Newly formed connective tissue tends to shrink. It strains the retina while doing so and may lead to retinal detachment. Neovascularization occurs in the iris and chamber angle (Rubeosis iridis). Here, the chamber water is prevented from flowing outside and glaucoma (secondary glaucoma) may develop. Diabetes mellitus is the most common cause of blindness in industrialized countries. An individual with diabetes carries a 25-fold higher risk of blindness compared to a healthy individual. If the macula is not affected by vessel damages and their outcomes, little to no symptoms are observed. If blood or water fills the macula, visual acuity decreases suddenly most of the time. Bleeding in the transluscent fluid leads to a darkening in the whole visual area. In the first stages of retinal detachment, there is only a minor visual ability and a risk of blindness. Retinal changes do not lead to pain. If there is secondary glaucoma, which mostly occurs together with increased intraocular pressure, pain may be felt.
The retina should be regularly examined in individuals with diabetes in order to detect presence of micro aneurisms, vessel damages, bleedings and neovascularization. For this examination, the opthalmologist uses an opthalmoscope, a microscope with a special lens or contact glass. In addition, dye substance test is applied to better evaluate the vessels according to the findings. Each diabetic patient should be examined by an opthalmologist for at least once a year. If diabetic changes are observed in the eye, examinations should be performed with shorter intervals (1/2 year, ¼ year or with shorter intervals).
The condition in all opthalmological therapies is good regulation of the blood glucose. The most important treatment in diabetic retinal changes is laser coagulation performed in the retina (laser therapy).
In this way, neovascularization with its complications can be prevented normally. In advanced conditions, sometimes corpus vitreum-retina operation (Vitrectomy) may be necessary. Here, bleedings in the corpus vitreum are stopped and newly formed vessels and connective tissues are removed.