Eye disease and vision problems: an introduction
Vision problems are one of the most frightening complications of diabetes. We depend on our eyes to make our way in the world (in a very literal sense) and when our ability to see is threatened, it can have a profound effect on our well-being.
Diabetes (both type 1 and type 2) is associated with both short-term and long-term effects on our eyes. Diabetes is the most frequent cause of new cases of legal blindness in the US population. Blurred vision is one of the most common symptoms of poorly controlled blood glucose and can affect a person at any stage of diabetes. Long-term complications affecting vision, including cataracts, glaucoma, and retinopathy, can appear at different stages of diabetes.1
Vision loss due to diabetes can be prevented or slowed in most cases
The good news about diabetes and vision complications is that in most cases vision loss associated with diabetes can be prevented or slowed by:
- Controlling your blood sugar (as close to normal as possible)
- Getting regular check-ups and timely treatment when problems arise
If you have type 2 diabetes, your doctor will refer you to an ophthalmologist or an optometrist for an initial assessment after your diagnosis. This initial assessment will include a dilated and comprehensive eye examination to determine if there are signs of retinopathy. If there is no evidence of disease, you should have follow-up exams every 2 years. If there is evidence of retinopathy, you should be re-examined annually or more frequently if retinopathy is progressing. Your primary care provider (doctor, nurse practitioner [NP], or physician assistant [PA]) will be able to recommend an eye specialist who has experience in treating different forms of diabetic retinopathy. The key to diabetic eye care is catching complications early. For some of the worst diabetic vision problems, such as proliferative diabetic retinopathy and diabetic macular edema, if the complication is caught in the early stages, treatment can be very effective. For instance, more than 95% of severe vision loss due to retinopathy and more than 50% of moderate vision loss due to macular edema can be prevented using laser surgery techniques.1
How does diabetes affect the eyes?
To understand how diabetes affects the eyes it is necessary to understand some of the basics about the anatomy of the eye and how vision works. Our eyes function like a camera, with light passing through the clear structures of the eye (the cornea, lens, and vitreous gel) and getting focused on the light-sensitive tissue that lines in the inner surface of eye called the retina. The center of the retina is called the macula. The macula is responsible for seeing colors and fine details. The outer area of the retina, called the peripheral retina or the periphery, is responsible for peripheral vision and seeing in low light. The different muscles, ligaments, and nerves of our eye allow us to focus the light, move the eye, and control the size of the pupil (the opening in the center of iris). In an old-fashioned camera (the kind that uses film), light reflecting off an object would get focused on the undeveloped surface of film, leaving an image of whatever the photographer intended to capture. The eye works a little more like a digital camera, in terms of what happens to the reflected light when it hits the retina. The retina is covered with receptors called rods and cones that transform light into electrical signals that are sent by the optic nerve to an area of the brain called the visual cortex. The visual cortex then translates electrical signals from the eye into the visual image that we perceive in our mind’s eye.
Vision problems happen when changes affect any of the individual components of the eye, optical nerve, or visual cortex that are involved in vision. For example, clouding of the lens of your eye causes a cataract, glaucoma involves increased pressure within the eye causing damage to the optic nerve, and in diabetic retinopathy damage occurs to the retina resulting in gradual loss of vision.
The main vision complications of diabetes are: