Diabetic retinopathy: stages, causes and risk factors

Diabetic retinopathy is a complication of diabetes that affects the eyes.

It is caused by vascular damage to the retina, that is, to the nervous tissue located in the back of the eye.
In the initial phase, diabetic retinopathy causes no symptoms or only very mild visual disturbances.

In the final phase, however, diabetic retinopathy can lead to blindness.
Diabetic retinopathy can affect people with type 1 or type 2 diabetes.

As a rule, retinopathy occurs on both sides.

Effects of diabetes on the retina?

The retina is a light-sensitive layer of cells at the back of the eye that converts light into electrical signals.
The signals are sent to the brain via the optic nerve and the brain interprets them and produces the images you see.
To work effectively, the retina relies on a constant supply of blood and is supplied via a network of small blood vessels.
Over time, an increased level of sugar in the blood can close the blood vessels or cause bleeding.
This damages the retina and prevents proper functioning.

In addition, there is a risk of fluid accumulating in the center of the retina (macula), which is called macular edema and leads to decreased vision.


Classification of diabetic retinopathy

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

Neuropathy can cause changes in the eye, including:

  • microaneurysms, small bulges in the blood vessels of the retina, from which fluid often leaks;
  • Retinal hemorrhages: small amounts of blood leaking from the retina;
  • Hard exudates: Accumulations of cholesterol or other fats that are emptied to the retina with the blood.
  • Macular edema: Swelling or thickening of the macula, caused by fluid leaking from blood vessels of the retina.
    The macula does not function properly when it is swollen. Macular edema is the most common cause of vision loss in diabetic patients.
  • Macular ischemia: occlusion of the small blood vessels (capillaries). Vision is clouded because the macula does not receive enough blood to function properly.

Many people with diabetes have mild neuropathy, which usually does not affect vision. However, if vision is affected, the cause is edema and ischemia of the macula.

Proliferative diabetic retinopathy
Proliferative diabetic retinopathy is the evolution of non-proliferative diabetic retinopathy and occurs mainly when many blood vessels in the retina close and thus sufficient blood flow is prevented.
In an attempt to maintain blood flow in the affected zones, the body forms new blood vessels around the retina.
This phenomenon is called neovascularization.
However, these new vessels are abnormal, weak and vulnerable and do not provide sufficient blood flow to the retina.

Proliferative diabetic retinopathy can lead to more serious vision loss than non-proliferative diabetic retinopathy because it affects central and peripheral vision more.

Causes of diabetic retinopathy and risk factors

The progression of retinopathy is associated with the severity and duration of hyperglycemia.
If diabetes is diagnosed before the age of 30, 10% is neuropathy after 50 years, but after 30 years this figure rises to 90%.

There is no glycemic index threshold that predicts when diabetic retinopathy occurs.
High blood pressure and other cardiovascular risk factors can affect the onset and progression of retinopathy.
Kidney disease characterized by proteinuria and elevated urea/creatinine levels is a good parameter to predict the occurrence of retinopathy.

Pregnancy can be associated with rapidly progressive neuropathy, especially:

  1. is caused by severe retinopathy.
  2. if too few blood glucose checks are carried out after conception, during pregnancy or in the postpartum period.
  3. if the diabetes has been present for a long time.
  4. if the patient has hypertension (chronic or due to pregnancy).

Complications of proliferative diabetic retinopathy

  • Vitreous hemorrhage: The new blood vessels are tender and can bleed into the vitreous, a gelatinous mass located inside the eye.
    The bleeding prevents the light rays from penetrating to the retina.
    If the vitreous hemorrhage is small, you can see dark spots floating in the eye.
    A very heavy bleeding can completely obstruct vision and only reveal light and dark. Vitreous hemorrhage alone does not lead to constant vision loss.
    If the blood is removed, vision can be regained as before, unless the macula has been damaged.
  • Retinal detachment due to tensile forces between the vitreous body and the retina: The scar tissue from neovascularization contracts, causing wrinkling on the surface of the retina, which pulls it out of its normal position.
    Vision loss is more severe if the macula or some large areas of the retina have detached.
  • Neovascular glaucoma: If different retinal vessels close, neovascularization can occur in the iris (the colored part of the eye). In this case, the new blood vessels can interfere with the normal flow of fluid from the eye.
    There is excessive pressure in the eye. This situation is especially serious because it can cause damage to the optic nerve.


Stages of diabetic retinopathy

  1. The first stage is mild, non-proliferative retinopathy. In this first phase, there are some small swollen areas that resemble small balloons in the blood vessels of the retina.
  2. The second stage is moderate, non-proliferative retinopathy. As the disease progresses, some blood vessels that feed the retina close.
  3. The third stage is serious, non-proliferative retinopathy. Many blood vessels are occluded, hindering blood flow in various areas of the retina. These areas send signals to the body to form new blood vessels for nutrient supply.
  4. The fourth stage is proliferative retinopathy. In this advanced phase, signals are sent out from the retina to initiate the required supply of nutrients. This leads to the growth of abnormal and fragile blood vessels.

Symptoms of diabetic retinopathy

Until diabetic retinopathy reaches an advanced stage, it usually causes no symptoms.
If retinopathy is not detected and treated, it can lead to sudden blindness.
That’s why it’s important to have regular checkups if you have diabetes.

Other possible symptoms of advanced retinopathy:

  • Swimming spots in the visual field (flying mosquitoes),
  • blurred vision,
  • Decreased night vision,
  • Sudden loss of vision.

Diagnosis of diabetic retinopathy

Diabetic retinopathy can be detected during a complete eye examination.

The examination is mainly focused on the evaluation of the retina and macula and includes:

  • Analysis of the patient’s medical history to determine the visual disturbances, the presence of diabetes and other health problems that can affect vision.
  • Measurement of visual acuity to determine the limits of central vision.
  • Autorefractometry to determine the need for a change of glasses.
  • Evaluation of eye structures, including examination of the retina with dilated pupil.
  • Measurement of intraocular pressure.
  • Photograph of the fundus of the eye (retinography) to observe the changes in the retina over time.
  • Fluorescangiography of the retina, makes it possible to evaluate the changes in the retinal vessels. During the examination, a dye (fluorescein) is injected intravenously and then the fundus of the eye is photographed.
  • Optical coherence tomography (OCT), shows cross-sectional images of the retinal surface.

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