Diabetes mellitus (DM) or diabetes
is a disease that is characterised by increased sugar levels in the blood due to insufficient or reduced efficacy of one’s own insulin. The permanent elevated level of sugar in the blood causes changes to blood vessels. Changes to small blood vessels (so-called microangiopathy) are manifested in the main complications of a diabetic:
- pathological changes to the retina – diabetic retinopathy
- pathological changes to the kidneys – diabetic nephropathy
- changes to the peripheral nerves – diabetic neuropathy
Diabetic retinopathy (DR), namely diabetic macular edema and complications of the proliferative DR, is one of the most common causes of blindness in advanced countries, including Slovakia. The risk of blindness in diabetes sufferers is roughly 10-20 times greater than in non-sufferers. In diabetics the development of cataract and atherosclerosis is also much more common.
Diabetic retinopathy is indicated by pathological changes to the retina and the retina vessels, which occur as a result of the overall infliction of the vessels in the case of diabetes. In particular it affects the retina capillaries. The infliction can appear as the onset of small aneurysms on the retinal capillaries (micro-aneurysms), minor bleeding to the retinas (haemorrhages) – as a consequence of the mentioned small aneurysms bursting.
Damaged vessels can leak out. This leads to swelling in the retina (edema). Later proliferation of blood vessels (neovascularisation) on the retina may occur , and multiplication of the tissue and the condition may lead even to complete blindness.
Diabetic retinopathy does not hurt
In the beginning the disease displays no symptoms. DR progresses long-term without pain and without signs of vision deteriorating. This is what makes the disease so deceiving. At the time when it would be appropriate to start therapy, the patient usually has no subjective difficulties even though affliction of the retina may already be at an advance stage. Affliction of the retina can only be discovered by a doctor upon preventive examination of the eye-ground or based on reduced sharpness of vision at advanced stages. At the moment subjective symptoms appear, treatment is already much more difficult and less effective. It is not until advanced stages of the disease that sharpness of vision deteriorates. Sharpness of vision deteriorates when swelling occurs in the area of the macula lutea of the retina, because it is the very function of yellow pigments that is important for sharp vision. With diabetics of an older age in particular, deteriorated vision is often attributed to other causes, such as presbyopia or cataracts, and not to diabetes, because a person’s sharpness of vision gets worse with age. Normally only the focus at close range becomes worse, and this can be balanced by reading glasses. If reading glasses do not correct close vision, or distance vision also gets worse, the cause is a pathological change, which must be revealed by an expert.
Classification of diabetic retinopathy
The basic classification of DR is based on the severity of micro-vascular changes in the retina and on the presence of retinal neovascularisation. DR is referred to as non-proliferative, provided all changes (micro-aneurysms, bleeding, edema and more) are only in the retina. With proliferative DR newly formed vessels and fibrous tissue grow on the surface of the retina. Both phases, depending on the volume of changes in the retina, can be mild, medium, heavy to extreme. The part of the retina at the centre of the eye – macula lutea (macule) ensure vision sharpness and colour perception. If this part of the retina is swollen, we refer to it as macular edema. This is the most common cause for sight deteriorating in diabetics. Macular edema accompanies the non-proliferative phase of the disease more often, but it may occur also in the proliferative phase.