Diabetic retinopathy is the most common cause of blindness in individuals between 20 and 74 years old. Elevated blood glucose for prolonged periods of time causes damage to the retinal blood vessels (along with the kidneys and nerves). Such damage to the blood supply of the retina can result in abnormal bleeding, swelling of the retina, poor blood flow to the retina, and/or scarring of the retina.
Most sight-threatening diabetic problems can be prevented by laser treatment if it is given early enough. It is important to realize however that laser treatment aims to save the sight you have - not to make it better. The laser, a beam of high intensity light, can be focused with extreme precision. So, the blood vessels that are leaking fluid into the retina can be sealed.
Diabetic retinopathy is subdivided into two forms: non-proliferative diabetic retinopathy (NPDR) and a more severe form, proliferative diabetic retinopathy (PDR).
NPDR starts with damage to the retinal blood vessels from prolonged elevation of blood glucose. The blood vessels develop tiny weak areas called microaneurysms. Over time, these microaneurysms can rupture and leak. This can result in retinal bleeding, or hemorrhage. Fluid from the blood stream can also leak into the retina and cause swelling, a condition called macular edema. Fats and proteins from the blood stream may leak into the retina as well, and are referred to as hard exudates. Macular edema tends to cause central blurring of vision and/or distortion. Over time, poor blood supply can result in death of nerve cells responsible for fine vision (a process called macular ischemia); this can lead to a permanent central blind spot with corresponding untreatable decreased central vision.
After prolonged poor blood flow, the retina produces substances that promote the growth of new, abnormal blood vessels (a process called retinal neovascularization). Retinal neovascularization marks the shift from non-proliferative to proliferative diabetic retinopathy (PDR) and is a very serious condition. This development of new blood vessels may appear logical, as the old, original blood vessels are often permanently damaged and poorly functioning. However, the retinal neovascularization process tends to do more harm than good over the long-term. The new blood vessels are fragile and tend to bleed into the vitreous cavity, a condition termed vitreous hemorrhage. A vitreous hemorrhage can cause significant floaters in the vision (from floating blood cells) and may cause transient near-total blindness if the hemorrhage is particularly dense. The new blood vessels may also grow along the surface of the retina, scar, and contract; this can pull on the retina and cause a very serious condition called traction retinal detachment.
The most important aspect in the treatment of diabetic retinopathy is long-term control of blood glucose. Patients should monitor their glucose daily and follow their hemoglobin A1c level with their diabetes doctor. They should also control any coexisting conditions that can worsen retinopathy; these include hypertension and elevated cholesterol/lipids.
Retinal intervention is generally aimed toward preventing visual loss from macular edema and complications of proliferative diabetic retinopathy.