Diabetes and Blindness
Diabetes is linked to blindness because of a number of eye diseases that are directly related to having diabetes and especially to having diabetes that isn’t under the best of control. Diabetes can cause damage to most of the parts of the eye, including the optic nerve, lens, macula, and retina.
The four most common diseases that can be linked to blindness in diabetics include:
- Diabetic macular edema. Diabetic retinopathy can be linked to diabetic macular edema (DME), which is swelling of the macula of the retina.
- Diabetic retinopathy. This is when the high blood sugar levels adversely affect the blood vessels in the retina, which is the part of the eye that picks up light and allows us to see. Diabetic retinopathy is the most common reason why diabetics go blind.
- Cataracts. This is when the lens of the eye becomes cloudy. People with diabetes have a 2-5 times risk for cataracts when compared to non-diabetics. Cataracts often develop earlier in life in diabetics compared to non-diabetics.
- Glaucoma. This is when the pressure inside the eye becomes elevated, resulting in damage to the optic nerve. The optic nerve is the nerve that leads from the back of the eye to the brain and which allows use to see clearly. Diabetics have twice the risk of developing glaucoma.
Regardless of the type of diabetic eye disease you have, you are at risk for blindness or at least having an impairment in your vision.
Causes of Diabetic Retinopathy
Diabetic retinopathy is caused by elevated blood glucose levels that cause damage to the smallest blood vessels supplying the retina. Normally, the retina takes in light through the pupil and turns it into an electrical signal that travels from the optic nerve to the seeing parts of the brain.
Diabetic retinopathy can result in blood vessels in the retina to hemorrhage or leak fluid. This can lead to proliferation of capillaries in the retina to make up for the loss of blood supply to the retina. When diabetic retinopathy becomes advanced, there can be scarring of the retina as well as loss of the cells of the retina.
There are 4 stages to diabetic retinopathy:
- Mild non-proliferative retinopathy—there are areas of microaneurysms (balloon-like swelling) of the blood vessels of the eye that eventually leak fluid into the retina.
- Moderate non-proliferative retinopathy—the disease gets worse, causing distortion and swelling of the blood vessels to the eye. The blood vessels can fail to provide enough oxygen to the retina, causing diabetic macular edema.
- Severe non-proliferative retinopathy—this is when the blood vessels in the retina become blocked, resulting in a lack of oxygenation to the eye. This causes growth factors to become secreted that tells the retina to make new blood vessels to make up for those that are blocked.
- Proliferative diabetic retinopathy—this is the most advanced stage of diabetic retinopathy. Growth factors are secreted by the retina that cause proliferation of capillaries along the lining of the retina and in the vitreous of the eye. Fluid leaks into the eye and the fragile capillaries hemorrhage, affecting the vision. There is also an increased risk of retinal detachment in this phase.
Diabetic Macular Edema
This is when there is an excess of fluid in the macula of the eye. People need the macula of the eye in order to see things sharply, such as for recognizing people’s faces, reading, and driving. Diabetic macular edema is the most common reason why diabetics suffer from vision loss and blindness. About 50 percent of those who have diabetic retinopathy will also have diabetic macular edema. Diabetic macular edema is usually worse as the diabetic retinopathy worsens; however, you can get edema of the retina in the early stages of diabetic retinopathy as well.
Risk Factors for Diabetic Retinopathy
Those who have diabetes, whether it be type 1 diabetes, type 2 diabetes, or even gestational diabetes, have an increased chance of developing diabetic retinopathy. The longer a patient has diabetes, the greater are the chances of also having diabetic retinopathy. About 40-45 percent of diabetics will have some degree of diabetic retinopathy, although only about half have symptoms of the disease. Gestational diabetes can lead to an accelerated form of diabetic retinopathy or worsening of preexisting diabetic retinopathy.
Symptoms of Diabetic Retinopathy and Diabetic Macular Degeneration
Those who are in the earliest stage of diabetic retinopathy are generally asymptomatic. As the disease worsens, vision can be affected. Bleeding into the retina can cause “floaters” to appear in the visual field. Why they may clear up on their own, floaters can affect the diabetics ability to see clearly. If diabetic retinopathy is left unchecked, hemorrhaging can occur, increasing the chances of blindness. Diabetic macular edema usually causes blurry vision that is not usually irreversible.
Diagnosing Diabetic Retinopathy and Diabetic Macular Degeneration
An ophthalmologist is the doctor who usually diagnoses these conditions by performing a comprehensive eye exam with the pupils dilated to allow the doctor to see the entirety of the retina. Common testing for these diseases include:
- Visual acuity testing by measuring vision at different distances.
- Pupil evaluation done when the pupil is dilated.
- Tonometry, which measures the amount of pressure inside the eye.
- Optical coherence tomography, which is a sort of ultrasound of the eye that uses light waves rather than sound waves to see the inside of the eye.
The ophthalmologist performs a detailed eye exam with the pupils dilated to check to see if the retina has any changes associated with the retinal blood vessels, changes in the lens, swelling of the macula, leaking blood vessels, fatty deposits in the retina, or damage to the nerves in the retina.
If the doctor suspects diabetic retinopathy or diabetic macular edema, a fluorescein angiogram can be performed that looks specifically at the retina and any leaky blood vessels that might be present. During the test, a dye is injected into the diabetic person’s blood and pictures are taken to see the dye and its effects on the blood vessels.
Prevention and Treatment of Diabetic Eye Diseases
In some cases, the vision loss seen in diabetic retinopathy are irreversible. Early detection and management of the disease are necessary to reduce the chances of blindness. Because there are no symptoms of early diabetic retinopathy, the diabetic needs to have yearly eye exams involving dilation of the pupil so the ophthalmologist can see the entire retina and inspect it for damage. Women who are diabetic and who become pregnant should have a dilated eye exam as soon as they find out they are pregnant. More than one eye exam in pregnancy may have to be performed.
Once the diagnosis of diabetic retinopathy is made, the doctor can do laser treatments to destroy the new capillaries that are affecting the vision. A vitrectomy can be performed to get rid of blurriness in the eye. If the diabetic has cataracts, surgery can be done to remove the cataract. If the diabetic has glaucoma, eye drops and other medications can be performed that can reduce the pressure inside the eye.
References:
- Facts about diabetic eye disease. https://nei.nih.gov/health/diabetic/retinopathy. Accessed 5/28/16.