Diabetes is a chronic disease that can effect the health of the eye in different ways. If the blood sugar is very high swelling of the lens occurs and this makes the eye more near sighted. After the diabetes is brought under control the swelling resolves and vision normally returns to the patient's baseline level. In diabetes healing time is prolonged and infections can be slower to resolve, so if an eye develops one of these conditions it may be more serious.
However the most vision-threatening eye problems associated with diabetes are from damage to the retina. The retina is akin to the film in a camera, and so when this tissue is impaired the picture your eye takes can become compromised. In diabetes, retinal damaged can be caused by compromised blood vessels. These vessels leak fluid and blood cells into the retina and this process is called background diabetic retinopathy. When there are just a few leaks in the periphery of the retina, vision may not be perceptively affected, but when the swelling involves the macula which is the area of the retina used for seeing fine objects, distortion or blurring occurs. An individual may notice a wiggle in a straight line, see a black spot, or have difficulty reading. To precisely locate the leaks and areas of retinal swelling precise imaging is done which will help guide treatment and determine if the retinal swelling is resolving.
Background retinopathy is rare during the first 5 years of diabetes, however over 75% of diabetics have at least some vessel changes after 15 years of the disease. These changes are often more pronounced in individuals that have not been able to control their blood sugar in a satisfactory fashion. If vessel damage progresses portions of the retina will not get enough oxygen and the tissue reacts to this by developing new blood vessels. This process is called proliferative diabetic retinopathy. These new vessels often do not grow in the retina, but rather go into the large cavity of the eye that is filled with an optically clear substance called the vitreous. If these vessels bleed the eye can fill with blood and vision will be profoundly effected.
In the 19th century the ophthalmoscope was invented, and for the first time an ophthalmologist could get a clear image of the retina in a living person's eye. It was observed that if a significant amount of retinal tissue was replaced by a scar or failed to develop, that eye generally did not develop prolifeative retinopathy the way an eye did which had its full complement of retina. This is because when there is less retinal tissue to nourish, the damaged blood vessels of a diabetic can still supply enough blood to keep the limited amount of retina healthy. Consequently, attempts were made to cause retinal scars in eyes severely damaged by proliferative disease. At the beginning of the 20th century lenses which focused light on the retina were used. Later the carbon arc photocoagulator was employed, and in the ‘70s the argon laser replaced the carbon arc. With a laser minute, intense beams can be precisely directed to leaking and peripheral areas of the retina that are not critical to vision . This will help seal vessel leaks and / or decrease the total amount of retinal tissue and often the retinopathy regresses. When the proliferative changes are severe or long standing surgery may be needed to remove the abnormal blood vessels, scar tissue and blood filled vitreous.
During the last few years a new class of drugs referred to as anti vaso endothelial growth factors have become the initial mode of therapy for many individuals with diabetic retinopathy. These substances can block the development of new blood vessels and consequently help prevent retinal edema and bleeding.
The ideal scenario is either preventing or finding a permanent cure for diabetes and active research is progressing in these areas. If you have diabetes the interim step is trying to keep the retina from developing any damage. Blood sugar control, attention to diet, exercise, weight control. and the treatment of other problems such as hypertension and lipid abnormalities are all-important in attaining this goal. Prevention of the retinopathy is far more productive than treating it after the fact.
For more information. . .
The American Academy of Ophthalmology has a section devoted to diabetic eye diseases and their prevention, diagnosis and varying treatment options.
The National Eye Institute has pamphlets on diabetes and the eye. They include basic information about what the disease is, risk factors, diagnosis, treatment, and a short reference section to other sites.