Diabetic retinopathy is a retinal disorder seen in diabetic persons. Diabetes compromises the circulation in many parts of the body. Likewise, the blood vessels in the retina can be affected by diabetes. The circulation can be affected in several ways, including leakage of serum through leaky blood vessels (edema), closure or occlusion of blood vessels (ischemia), growth of abnormal new blood vessels (neovascularization), bleeding within the cavity of the eye (vitreous hemorrhage), and scar tissue pulling the retina out of position (retinal detachment).

The less severe type of diabetic retinopathy is called non-proliferative diabetic retinopathy. The more advanced type of diabetic retinopathy is called proliferative diabetic retinopathy. Non-proliferative diabetic retinopathy is far more common than proliferative diabetic retinopathy. It is called non-proliferative because there are no proliferating blood vessels (neovascularization) growing in the retina, whereas proliferative diabetic retinopathy is characterized by the growth of abnormal blood vessels. The abnormal vessels do not help the circulation, but rather they result in complications, such as bleeding into the eye ball (vitreous hemorrhage) and pulling on the retina (retinal detachment). Non-proliferative diabetic retinopathy is characterized by milder retinal changes. These include small spots of hemorrhage in the retina, poor circulation, and retinal blood vessels which leak serum, resulting in lipid deposits (exudate) or swelling (edema).

The earliest stages of diabetic retinopathy are too mild to affect the sight. However, many patients with significant diabetic retinopathy have no symptoms at all. This is possible for several reasons. Visual loss in one eye can be present, but might go unrecognized unless the good eye was covered. Alternatively, it is not unusual to have diabetic retinopathy which is threatening the vision, but has not yet caused a noticeable problem. For example, swelling of the retina (edema) would not cause a noticeable disturbance of vision unless the macular center (the one spot in the retina we use for reading) was involved. When the macular center is swollen, one notices blurred vision. Likewise, patients with proliferative diabetic retinopathy would not be aware of abnormal blood vessels (neovascularization) until after they bleed (vitreous hemorrhage). Bleeding in the eye would be perceived as floating spots or strands in the field of vision, or dark areas blocking the sight. It is important to understand that lack of symptoms does not mean lack of retinopathy!

The answer to this question is still not known. There are many possible explanations and a lot of research is ongoing. The following explanation is a simplification of a complex process. High blood sugar levels over a period of years results in changes in the blood vessel walls. The end result is loss of watertight seals in the vessel walls, allowing leakage of serum, closure of blood vessels resulting in oxygen-starved retinal tissue, and growth of new blood vessels as a consequence of poor circulation.

Most patients with diabetic retinopathy retain good vision throughout their lives. Maintaining good blood sugar control, good blood pressure control and good cholesterol levels helps to protect against diabetic retinopathy. For patients with advancing diabetic retinopathy, the prognosis for vision has improved significantly since the advent of laser treatment in the 1970's. Before laser treatment was available, eyes with proliferative diabetic retinopathy routinely suffered severe visual loss. Laser treatment lowers the risk of severe visual loss by more than half. Likewise, eyes with leakage involving or threatening the macular center have half the risk of visual loss after laser treatment than without laser treatment. Our greatest challenge now is ensuring that diabetic patients have their eyes properly examined so that diabetic retinopathy, if present, can be identified, staged, and treated in a timely fashion. Simply put, the best way for diabetics to improve their prognosis is to have a dilated eye examination!

The best way to diagnose diabetic retinopathy is with a dilated eye examination at an eye doctor's office. Patients cannot assume that they have no diabetic retinopathy if their vision is normal. Significant and potentially blinding diabetic retinopathy can be present in eyes with 20/20 vision! It is recommended that diabetics have dilated eye examinations every year. A comprehensive eye examination with dilating drops should take less than an hour. The dilating drops wear off after several hours. It is best for the patient to have a driver and to bring sunglasses to wear home after the exam. If retinopathy is present, your eye doctor may want to obtain a test called OCT and/or fluorescein angiography to study the retinal circulation in greater detail.

Most diabetic retinopathy can be safely observed because the mildest grades of retinopathy pose no threat to a patient's vision. However, clinically significant macular edema is diagnosed when leakage of serum creeps close to the macular center at which time focal laser treatment is considered. If proliferative diabetic retinopathy (new abnormal blood vessels) is present, panretinal or scatter laser treatment is advisable. Laser treatment can be applied in the office and does not require incisions or sutures. Laser is a microscopic beam of light which can be used to stop leakage from affected vessels or cause new blood vessels to shrink away. Laser treatment can be applied in a manner which the patient does not feel. A surgical procedure called vitrectomy is available for eyes with more severe retinopathy, such as bleeding (vitreous hemorrhage) or pulling (retinal detachment).