What Are the Different Types of Diabetic Retinopathy?
There are two different types of Diabetic Retinopathy, namely
- Non-proliferative Diabetic Retinopathy (NPDR)
- Proliferative Diabetic Retinopathy (PDR)
Non-proliferative Diabetic Retinopathy (NPDR)
Non-proliferative diabetic retinopathy, also known as background retinopathy, is the early stage of diabetic retinopathy. Over time, diabetes causes changes in the tiny blood vessels that nourish the retina. It occurs when the retinal blood vessels start to leak, causing blood or fluid to seep into the retina. You may find it difficult to recognize people’s faces. The retina becomes thick and swollen and does not work correctly. If the leaks happen in the macula, (the central part of the retina), vision will be blurred. If the leaks occur on the periphery of the retina, there may be no impact on vision.
Many people with diabetes have mild NPDR, which usually does not affect vision. However, there are two forms of NPDR that can cause vision loss:
- Macular Edema is swelling of the macula, a small area in the center of the retina that allows us to see fine details (like letters or numbers) clearly in the center of our vision. The swelling is caused by fluid leaking from retinal blood vessels. It is the most common cause of visual loss in diabetes. The amount of central vision that is lost varies from person to person. However, the vision that allows you to get around at home and outside (peripheral vision) will be preserved. Reading and close work may become more difficult because of this condition.
- Macular ischemia occurs when small blood vessels feeding the macula close off. Due to insufficient blood supply to macula, the cells in the macula no longer work correctly, which causes vision to blur.
Proliferative Diabetic Retinopathy (PDR)
When retinopathy advances, the decreased circulation of the blood vessels deprives areas of the retina of oxygen. Blood vessels become blocked or closed, and parts of the retina die. New, abnormal, blood vessels grow to replace the old ones. This is called proliferative diabetic retinopathy, and is nature way of trying to repair the damage so that the retina has a new blood supply. It affects up to 20% of diabetics and can cause severe loss of sight, including blindness.
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. If the vitreous hemorrhage is small, a person might see only a few new dark floaters. A very large vitreous hemorrhage might block out all vision. Blood can generally clear up over several months, but if it does not, surgical removal of the vitreous, called vitrectomy, can be performed.
- 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.
- 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.
