Diabetic retinopathy is the main eye disorder caused by diabetes mellitus, and in industrialized countries it is the leading cause of blindness in people of working age. Symptoms associated with it often appear late, when lesions are already advanced, which limits the efficacy of treatment.

Diabetes is a disease characterized by high blood sugar (hyperglycaemia), due to an absolute or relative insulin deficiency (insulin is a hormone produced by the pancreas which processes sugar). Two forms of diabetes are currently recognized: type 1 affects mostly children and adolescents and is due to the destruction of the insulin-producing ß cells of the pancreas, while type 2 affects mostly adults and is characterized by the insufficient production of insulin on the part of beta cells and/or the failure to use insulin properly.

Epidemiological notes

In Italy, there is neither data on the prevalence and incidence of legal blindness (residual vision no higher than 1/20 in the best eye) in diabetic patients, nor a register of subjects affected by diabetes mellitus. There are nevertheless epidemiological data which show that at least 30% of diabetics suffer from retinopathy, and that every year 1% of diabetics are affected by the most severe forms of retinopathy. The main risk factors associated with an early onset and rapid evolution of retinopathy are the duration of diabetes, the glycemic imbalance and any resulting arterial hypertension, in patients with either type 1 and type 2 diabetes. The prevalence of diabetes in Italy is estimated at 3-4% of the population and it increases with age. This means that about 180,000 people suffer from diabetes in Latium, of which 50,000-90,000 are affected by diabetic retinopathy. About 1 in 10 cases involves type 1 diabetes. Additionally, it is estimated that between one-third and one-half of type 2 diabetes have not yet been diagnosed, since they are asymptomatic.  Projections by the World Health Organizations (2) suggest that the number of diabetes cases in Europe will double by 2025, due to an increase in risk factors such as an aging population, sedentary lifestyles, and poor eating habits.

Risk factors

The main risk factors associated with an early onset and rapid evolution of diabetic retinopathy are the duration of diabetes, the glycemic imbalance and any resulting arterial hypertension. Without a doubt, the main risk factor that can be modified is glycemic control. It has also been clearly shown that by optimizing the control of glycemia and, if present, arterial hypertension, the onset of retinopathy can be delayed and its progression slowed.

Clinical classification

Diabetic retinopathy is classified in two forms, an early and less serious form (non-proliferative) and an advanced form (proliferative). If the former is not diagnosed and treated in a timely manner, it evolves into the second, highly debilitating form. In non-proliferative diabetic retinopathy (which can in turn be sub-divided into slight, moderate, or advanced), hyperglycaemia damages the structure of blood vessels, paving the way for the formation of micro-aneurysms, micro-haemorrhages and intraretinalmicrovascular anomalies (IRMA). These anomalies can lead to certain blood components responsible for edemas and exudative phenomena to pass through the damaged walls of these vessels, or to a reduced perfusion of the retinal tissue, ultimately leading to complete ischemia, which initially manifests itself with the presence of cotton wool exudate. Diagnosing an advanced non-proliferative retinopathy is important since we know that if left untreated, it evolves into proliferative diabetic retinopathy within 12 months in 40% of cases. The occlusion of retinal capillaries and the resultant formation of ischemic areas in the retina is a stimulus for the formation of retinal neovessels, which characterize the proliferative form. Since the structure of these new blood vessels is inadequate, they can break easily, with the risk of pre-retinal and endovirtealhaemorrhage and secondary retinal detachment.

Diagnosis

In its early stages, diabetic retinopathy is generally asymptomatic. However, the lack of symptoms does not indicate  the absence of diabetic retinal microangiopathy, since loss of vision, which is the first symptom a patient becomes aware of, only occurs once the macular region (central part of the retina) is affected. The latter situation can be an early sign of diabetic retinopathy, but it can also fail to be present even in advanced stages of proliferative and non-proliferative retinopathy. Blindness from diabetic retinopathy could be avoided in over half of all cases if patients are adequately informed and if suitable health education measures are implemented, which measures are of key importance for the success of any policies to prevent damage to vision from diabetes. Screening of ocular complications, performed by trained personnel using proven techniques, allows for the early diagnosis of high-risk diabetic retinopathy, and thus helps prevent vision loss. A digital national register of diabetic patients would make it possible to identify all citizens in need of screening, and to implement the adequate quality control procedures for the programme.  An early and precise diagnosis of diabetic retinopathy is therefore essential for preventing ocular damage, which in extreme cases can lead to blindness.
To prevent or fight possible damage from diabetic retinopathy, it is advisable to undergo periodic ophthalmological checkups including a dilated eye exam, and to keep glycemia and systemic arterial pressure under control. A key step in diagnosing and establishing the degree of retinopathy is the fluoroangiographic exam, which makes it possible to study in detail the morphological and functional changes in the retinal vessels, and providing indispensible indications in case of laser treatment. Other useful diagnostic exams for managing diabetic retinopathy are ophthalmic ecographies (especially in complex, advanced forms), optical coherence tomography (OCT) and microperimetry.

Treatment

As stated above, the most efficient ways to reduce the frequency of the onset of diabetic retinopathy, and to prevent it from becoming more serious, are careful prevention and  rigorous metabolic compensation.
In case of complications affecting the eyes, efficient interventions, depending on the specific situation at hand, may include:

  • Targeted laser treatment, which is effective in improving recovery of vision in edematous forms, and in reducing the severe complications associated with proliferative neovascular forms.
  • Intra-vital injections of Ranibizumab or Aflibercept useful in regressing neovases, in forms refractory to laser treatment and in edematous forms of a certain magnitude (>400 microns central thickness of the macular region at oct examination)
  • Intra-vitreal implant of slow release dexamethasone that exploits the antiangiogenic and anti-edemigenous action properties of corticosteroids in diabetic macular edema forms.
  • Vitreous-retinal surgery, which is generally reserved for the most serious cases (proliferating regenerative lymphatic hemorrhages with recurrent vitreous hemorrhages and/or traditional retinal detachment).