Diabetic Retinopathy Classifications

Diabetic Retinopathy

Last updated on June 13th, 2016

Diabetic retinopathy is the most common eye complication of type 1 and type 2 diabetes.  Diabetic retinopathy happens when there are changes in the blood vessels in the retinas of people who have elevated blood glucose levels.  The blood vessels of the person with diabetes have a tendency to leak fluid, swell, or have the blood vessels become blocked with atherosclerosis.

In other situations, the diabetic can have the formation of new blood vessels on the retinal surface that interferes with the diabetic’s ability to see so that blindness can occur. Normally, diabetic retinopathy is worse in those diabetics who do not have good blood sugar levels on a regular basis.

In normal people, the retina is the area of the back of the eye that responds to light entering through the pupils.  The rays of light enter the pupil and are focused by the lens onto the retinal surface. From there, the retina sends signals to the brain, where the brain interprets the light signals into actual visual pictures that the person sees.

The macula is part of the retina that is responsible for seeing the finer details in the vision.  It is a small part of the retina and is the part that allows for seeing fine details for things like reading, sewing, seeing sharp images on the television, and recognizing details in another person’s face. Outside of the macula, the rest of the retina is used for peripheral (side) vision.

Diabetic retinopathy usually involves damage to both eyes at the same time.  The diabetic who has early stage diabetic retinopathy may not have any symptoms or they can have slightly blurry vision.  As the disease becomes worse, the vision worsens so that, if the disease is left unchecked, blindness and reduction in the ability to see fine detail is lost.  When the diabetic retinopathy is at its worst, the changes are often irreversible and the person will be permanently affected.

Types of Diabetic Retinopathy

There are two classifications of diabetic retinopathy:

Nonproliferative diabetic retinopathy (NPDR).

This is the earliest stage of the disease.  In a person with nonproliferative diabetic retinopathy, the diabetic has edema and the leakage of small amounts of blood in and around the retinal tissues.  There can be cholesterol deposits in the blood vessels supplying the eyes and the presents of blood fats that have leaked from the blood vessels into the retinal tissue.

Nonproliferative diabetic retinopathy can cause changes in the diabetic’s retina, including the development of microaneurysms or small bulges in the tiny blood vessels supplying the retina.  The areas involved with microaneurysms often leak fluid, reducing the diabetic’s ability to see clearly.

Other things that can come out of nonproliferative diabetic retinopathy include the development of tiny hemorrhages in the retina of the eye, macular edema, which is swelling or thickening of the tissues of the macula caused by leakage of fluid from the blood vessels of the retina.  Macular edema is extremely common and is the most common reason why a diabetic has poor vision.

In nonproliferative diabetic retinopathy, there can also be deposits of fats, including cholesterol, that leak into the retina, resulting in what is known as “hard exudates”.  When the nonproliferative diabetic retinopathy becomes more severe, the macula can have a reduction in the blood flow in the small vessels supplying the macular cells.  The vision becomes blurry because the macular cells have died off from a lack of circulation. This is usually irreversible.

When a diabetic has had about 20 years of elevated blood sugars, the chances of having nonproliferative diabetic retinopathy are high.  This usually is asymptomatic unless the person has already developed macular edema.  If the nonproliferative diabetic retinopathy is left untreated, it passes on to the next stage.

Proliferative Diabetic Retinopathy.

Proliferative diabetic retinopathy is more serious than nonproliferative diabetic retinopathy. During the proliferative stage, more blood has leaked into the retinal tissue and into the vitreous, which is the gelatinous substance that is inside the globe of the eye. As a result of a lack of circulation to the retina, the retinal tissue develops new blood vessels that cover the retinal tissue, interfering with vision.

The relatively fragile capillaries in the proliferative stage of diabetic retinopathy tend to bleed more than normal capillaries. Not only the capillaries themselves cause the retina to be unable to see clearly, but the bleeding of these delicate blood vessels covers the retinal tissue, resulting in blurring of the vision.

Macular edema can be seen in proliferative diabetic retinopathy but it can also be seen in nonproliferative disease.  When macular edema develops, the ability to see clearly is threatened and the ophthalmologist may have to use laser surgery to burn away the proliferation of capillaries that are interfering with the vision and function of the retina.

In proliferative diabetic retinopathy, the vision can be threatened in more than one way.  Not only is it threatened by macular edema and the proliferation of new blood vessels (capillaries), but, when the body attempts to heal the bleeding areas, scar tissue can develop, which pulls on the retinal tissue, resulting in the increased chance of retinal detachment.  Retinal detachment can lead to permanent blindness.

Curing Diabetic Retinopathy

Diabetic retinopathy of either stage cannot be cured but can be prevented through maintaining normal blood glucose levels.  When the blood glucose levels are maintained in the normal range, the circulation to the eye is better and the chances of microaneurysms, macular edema, macular ischemia, bleeding into the retina and vitreous, and retinal detachment are much less.  This is why it is important to keep the blood sugars under the best of control in both type 1 and type 2 diabetes mellitus.

Complications of Diabetic Neuropathy

If the diabetic cannot maintain normal blood sugars, the chances of diabetic neuropathy are high and the diabetic can have several complications, including the following:

Vitreous hemorrhage.

This is a complication of proliferative diabetic retinopathy.  It occurs when the new capillaries bleed into the gelatinous substance that make up the inside of the globe of the eye.  The main symptoms are a lack of clear vision and the presence of floaters in the eye.  If the bleeding is extensive, the diabetic’s vision may become extremely limited so that they can only differentiate between light and dark and cannot see any objects clearly.

Traction retinal detachment.

This is when the new blood vessels heal, leading to scar tissue that pulls on the retina.  It can pull on the retinal tissue so much that the retina detaches from the rest of the eye ball, resulting in permanent vision loss.

Neovascular glaucoma.

If the retinal blood vessels become blocked, new blood vessels can form in what is known as neovascularization. This can occur in the iris of the eye, blocking the flow of fluid from inside the eye to the outside of the eye.  The end result is a buildup of pressure inside the eye, a condition known as neovascular glaucoma.

Image source: Wikipedia

References:

  1. What is diabetic retinopathy? http://www.aao.org/eye-health/diseases/what-is-diabetic-retinopathy. Accessed 5/31/16.
  2. Diabetic Retinopathy: Your Questions Answered. http://www.joslin.org/info/Diabetic_Retinopathy_What_You_Need_to_Know.html.  Accessed 5/31/16.
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