It is caused by damage to the blood vessels of the retina, ie the nerve tissue located at the back of the eye. 
In the final stage, however, diabetic retinopathy can cause total loss of vision.

Diabetic retinopathy can affect anyone who has type 1 or type 2 diabetes . 
Usually retinopathy is bilateral.

Effects of diabetes on the retina

Diabetic retinopathy

The retina is a layer of sensitive cells in the back of the eye that converts light into electrical signals.

The signals are sent to the brain through the optic nerve and the brain interprets them to produce the images we see. 
To work effectively, the retina needs a constant supply of blood that it receives through a network of small blood vessels. 
Over time, a consistently high blood sugar level can cause blockage of blood vessels or bleeding . 
This damages the retina and prevents proper functioning.

In addition, there is also the risk of fluid accumulation (edema) in the macula (the central area of ​​the retina), which causes a reduction in vision.


Classification of diabetic retinopathy

Non-proliferative diabetic retinopathy

Non-proliferative diabetic retinopathy is the earliest stage of the disease.

Retinopathy can cause eye disease, including:

  • The microaneurysms are small lumps in the blood vessels of the retina which the fluid exits often;
  • Retinal hemorrhage : small amounts of blood coming out of the retina;
  • Hard exudates : deposits of cholesterol or other fats that are discharged into the retina of the blood.
  • Macular edema : The swelling or thickening of the macula is caused by fluid coming out of the vessels of the retina. 
    The macula does not work properly when it is swollen. Macular edema is the most common cause of vision loss in diabetics.
  • Macular ischemia : closure of small blood vessels (capillaries). The sight is disturbed because the macula does not get enough blood to function properly.

Many people with diabetes have mild neuropathy that usually does not affect vision. However, if sight is affected, the result is edema and macular ischemia.

Proliferative diabetic retinopathy

Proliferative diabetic retinopathy is the evolution of proliferative diabetic retinopathy, especially when many blood vessels in the retina are closed, preventing a sufficient flow of blood. 
In an attempt to keep the blood supply in the area where the vessels are closed, the body creates new blood vessels around the retina. 
This phenomenon is called neovascularization. 
However, these new blood vessels are abnormal, weak, subject to rupture and do not give the retina sufficient blood flow.

Proliferative diabetic retinopathy can cause more severe vision loss than nonproliferative diabetic retinopathy because it affects central and peripheral vision.


Causes and risk factors of diabetic retinopathy

The progression of retinopathy is related to the severity and duration of hyperglycemia . 
If diabetes is diagnosed before age 30, the incidence of neuropathy after 10 years is 50%, but rises to 90% after 30 years. 
There is no glycemic index threshold that predicts if and when diabetic retinopathy will occur. 
The hypertension and other cardiovascular risk factors can influence the onset and progression of retinopathy.

A kidney disease, as evidenced by proteinuria and high levels of urea / creatinine is an excellent element to predict the onset of retinopathy. 
Pregnancy may be associated with a rapid progression of neuropathy, particularly if: 
1. There is severe retinopathy. 
2. There is a decrease in glycemic control during conception, during pregnancy or in the postpartum period. 
3. Diabetes has been around for a long time. 
4. The patient has high blood pressure  (chronic or due to pregnancy).


Complications of proliferative diabetic retinopathy

1. Vitreous haemorrhage : New blood vessels are delicate and may bleed into the vitreous body, ie a mass of gelatin that is located inside the eye. 
Bleeding prevents light rays from reaching the retina. 
If the vitreous hemorrhage is small, dark spots or moving shadows can be seen in the field of view. 
A very large bleeding can completely block the vision and allow to perceive only light and dark. The vitreous hemorrhage alone does not cause permanent loss of vision. 
When blood is removed, vision may return to the previous level unless the macula has been damaged .

2. Retinal detachment by vitreoretinal traction: Scar tissue from neovascularization shrinks, causing wrinkling of the surface of the retina that is  pulled from its normal position. Vision loss is most severe if the macula or some large areas of the retina stand out.

3.  Neovascular glaucoma : if different vessels of the retina close, neovascularization can occur in the iris (the colored part of the eye). In this situation, new blood vessels can block the normal flow of fluid out of the eye. 
Excessive pressure builds up in the eye, this is particularly serious because it can cause damage to the optic nerve.

Phases of diabetic retinopathy

1. The  first stage  is mild non-proliferative retinopathy. At this early stage, there are small, balloon-like areas in the blood vessels of the retina. 
2. The  second stage  is moderate non-proliferative retinopathy. With the progression of the disease, some blood vessels that nourish the retina are blocked. 
3. The  third stage  is severe non-proliferative retinopathy. Many vessels are blocked and block blood flow to different areas of the retina. These areas send signals to the body to create new blood vessels for food. 
4. The fourth phase is proliferative retinopathy. At this advanced stage, the retinal signals to get the required nutrient intake can cause the growth of new abnormal and fragile blood vessels.


Symptoms of diabetic retinopathy

Usually diabetic retinopathy does not cause obvious symptoms until it has reached an advanced stage. 
If retinopathy is not identified and treated, it can lead to sudden blindness. 
This is why it is very important that people with diabetes have regular ophthalmic appointments.

Other symptoms of advanced retinopathy may be:

  • Floating points in the visual field (flying flies),
  • Blurred vision,
  • Reduced night vision,
  • Sudden loss of vision.


Diagnosis of diabetic retinopathy

Diabetic retinopathy can be diagnosed with a complete ophthalmic examination. 
The test is mainly focused on the evaluation of the retina and macula, and includes:

  • Analysis of the patient’s medical history to determine the difficulty of the vision, the presence of diabetes and other health problems that can affect vision.
  • Measure of visual acuity to determine the extent of central vision.
  • Autorrefratometria , to determine the need for changes in prescription of glasses.
  • Evaluation of ocular structures , including evaluation of the retina with the dilated pupil.
  • Measurement of pressure  in the eye.
  • Fundus – Photography fundus  to evaluate the retinal changes over time.
  • Angiofluoresceinography of the retina : allows to evaluate the alterations of the blood vessels of the retina. It is performed by injecting a dye (fluorescein sodium) intravenously and then the background is photographed.
  • The tomography optical coherence (OCT) showing the surface of the retina.

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