Diabetes-related eye diseases include a group of disorders that can cause partial or total loss of vision; among them are diabetic retinopathy, cataracts, and glaucoma. All are typically associated with periods of high blood glucose levels as well as with high blood pressure.
Retinopathy. The term “retinopathy” means “disease of the retina,” and the type of retinopathy that is associated with diabetes is often referred to as “diabetic retinopathy.” Both high blood glucose levels and having had diabetes for a long time raise the risk of developing diabetic retinopathy. In retinopathy, the blood vessels in the retina are damaged. Two types of changes in the retinal blood vessels can occur as complications of diabetes: nonproliferative retinopathy (also called background retinopathy), and proliferative retinopathy.
In nonproliferative retinopathy, small blood vessels in the retina swell, weaken, and leak blood and fluid into the posterior chamber of the eye. The retinal tissues become swollen, and when the area of the retina called the macula is affected (a condition called macular edema), the result is blurry vision and sometimes changes in color perception. However, in its early stages, nonproliferative retinopathy may cause no symptoms at all.
In proliferative retinopathy, fragile, new blood vessels form and grow over the retina. The new blood vessels often leak blood into the vitreous humor, causing cloudy vision. The formation of new blood vessels can also lead to scarring, which can pull on the retina, leading to retinal detachment and loss of vision. If a detached retina is treated early, vision often returns to normal, but in advanced cases, vision loss can be permanent.
Both nonproliferative and proliferative retinopathy can be treated with laser photocoagulation, in which laser beams are used to seal leaky blood vessels and destroy abnormal new blood vessels. If a large amount of bleeding has occurred as a result of retinopathy, a vitrectomy, in which the vitreous humor is removed and replaced with a saline solution or other substance, may also be performed.
Cataracts. A cataract is a clouding of the lens in the eye. While many people will develop cataracts if they live long enough, those with diabetes tend to develop cataracts at an earlier age. In fact, having diabetes is considered a risk factor for the development of cataracts. Symptoms of cataracts include the following:
- Cloudy or blurry vision
- Changes in color vision (colors may appear faded or yellowish)
- Increased sensitivity to light (lights appear too bright)
- A glare or halo effect around lights
- Poor vision, especially at night
- Double vision or multiple images in one eye, which may actually get better as the cataract gets larger
- Frequent changes in eyeglass or contact lens prescriptions
The treatment for cataracts is surgical removal of the cloudy lens and, generally, replacement with an artificial lens. According to the National Eye Institute, cataract surgery results in improved vision in 90% of cases. When to have surgery is typically decided by the person who has the cataract and the physician treating the eyes. Surgery usually is scheduled when vision becomes impaired enough to interfere with activities of daily living or to pose a threat to personal safety or when discomfort occurs. A cataract may also be removed if it interferes with examination or treatment of another eye problem. Before surgery, some people with cataracts benefit from adding or changing prescription eyewear, using sunglasses to diminish bright light, and/or adjusting the lighting in their homes and work environments.
Glaucoma. The most common type of glaucoma in people with diabetes is called open-angle glaucoma, and it occurs when the fluid pressure inside the eyes rises, resulting in damage to the optic nerve. It can ultimately cause loss of vision. Glaucoma has no symptoms in its early stages. As the disease progresses, a person’s peripheral (side) vision may decrease. If the glaucoma continues without treatment, tunnel vision can occur, with an eventual loss of sight.