Diabetic retinopathy occurs when diabetes damages the tiny blood vessels in the retina. At this point, most people do not notice any changes in their vision.
Some people with diabetic retinopathy develop a condition called macular edema. It occurs when the damaged blood vessels leak fluid and lipids onto the macula, the part of the retina that lets us see detail. The fluid makes the macula swell, blurring vision.
As the disease progresses, it enters its advanced, or proliferative, stage. Fragile, new blood vessels grow along the retina and in the clear, gel-like vitreous that fills the inside of the eye. Without timely treatment, these new blood vessels can bleed, cloud vision, and destroy the retina.
What Are the Different Types of Diabetic Retinopathy?
Non-proliferative Diabetic Retinopathy (NPDR)
Non-proliferative diabetic retinopathy, also known as background retinopathy, is the early stage of diabetic retinopathy. In this stage, tiny blood vessels in the peripheral retina leak blood and fluid.
People with non-proliferative diabetic retinopathy may experience no difficulties with vision. However, those who do experience problems are those who develop macular edema or macular ischemia.
- Macular edema occurs when the macula, the small area in the center of the retina that provides central detail vision, can swell from the leakage of blood and fluid from blood vessels in the retina. Central vision loss may be mild to severe, and side (peripheral) vision loss can also occur. Reduced sensitivity to color is also a result.
- Macular ischemia occurs when small blood vessels feeding the macula close off. Because the macula doesn’t receive sufficient blood, the cells in the macula no longer work correctly, which causes vision to blur.
Proliferative Diabetic Retinopathy (PDR)
Proliferative diabetic retinopathy is the more severe stage of the disease when abnormal blood vessels grow into the retina or optic nerve. Because the disease can cause much of the circulation of the retina to close down, abnormal blood vessels grow into the retina to augment the reduced blood flow. Unfortunately, these abnormal vessels do not re-supply the reduced blood flow. These vessels are often fragile or accompanied by scar tissue, which may cause the retina to pull away from the wall of the eyeball — causing retinal detachment or retina hemorrhage.
Because abnormal blood vessels can grow in any part of the retina, not just the macula, both central and peripheral vision is affected with proliferative diabetic retinopathy. PDR can cause one of the following complications leading to potential vision loss:
- Vitreous hemorrhage
One of the complications of proliferative diabetic retinopathy is hemorrhage from fragile blood vessels leaking into the vitreous, the clear gel-like substance that fills the interior of the eye. If blood clouds the vitreous, light passing from the lens through the vitreous to the retina is blocked, and vision is markedly reduced. Blood can generally clear up over several months, but if it does not, surgical removal of the vitreous, called vitrectomy, can be performed. Specialists in vitreo-retinal surgery can remove blood and scar tissue from the eye and replace the vitreous with a clear solution. This may result in useful, though reduced, vision.
- Secondary glaucoma
Secondary glaucoma is also known as neovascular glaucoma. With this complication, fragile new blood vessels in the eye may form a new network directly on the iris, blocking the outflow of fluid from the eye. This condition results in elevated pressure of the fluids within the eye, and can cause optic nerve atrophy and loss of the full visual field. Treatment involves the application of laser to the leaking areas. Standard glaucoma treatment with drops or diuretics may also be recommended to lower intraocular pressure. For more information on glaucoma click here (LINK).
- Retinal detachment
The abnormal blood vessels that grow in proliferative diabetic retinopathy are often accompanied by hemorrhage and scar tissue formation. This scarring can cause wrinkling of the retina and even separation from the wall of the globe. This is known as retinal detachment. Wrinkling of the retina can result in visual distortion whereas retinal detachment can cause severe vision loss depending on where the separation has occurred.
With diabetes, you may notice no changes in your vision at first. However, uncontrolled diabetes can gradually get worse over the years and threaten your good vision.
Diabetic retinopathy often has no early warning signs. At some point, though, you may develop macular edema, which can blur vision, making it hard to do things like read and drive. In some cases, your vision will get better or worse during the day.
As new blood vessels form at the back of the eye, they can bleed (hemorrhage) and blur vision. The first time this happens it may not be very severe. In most cases, it will leave just a few specks of blood, or spots, floating in your vision. They often go away after a few hours.
However, gradually these spots are followed within a few days or weeks by a much greater leakage of blood. The blood will blur your vision.
In a vitreous hemorrhage, a person will only be able to tell light from dark in that eye. It may take the blood anywhere from a few days to months — or even years — to clear from the inside of your eye. In some cases, the blood will not clear spontaneously and must be surgically removed by vitrectomy.
Diabetic retinopathy is detected during an eye examination that includes:
- Visual acuity test
This eye test, which measures how well you see at various distances, has two components. It measures accurate vision without correction as well as best corrected vision confirmed by refraction.
- Pupil dilation
The eye care professional places drops into the eye to widen the pupil. This allows the doctor to see more of the retina and look for signs of diabetic retinopathy. After the examination, close-up vision may remain blurred for several hours.
This is an examination of the retina in which the eye care professional: (1) looks through a special magnifying lens that provides a narrow view of the retina, or (2) wearing an indirect ophthalmoscope with a bright light, looks through a special magnifying glass to gain a wide view of the retina.
A standard test that determines the fluid pressure inside the eye. Elevated pressure is a possible sign of secondary glaucoma, another common eye problem in people with diabetes.