Diabetes is an extremely common disease affecting approximately 24 million Americans. Over years, diabetes can cause damage to various body organs and tissues. Some of the most common complications associated with diabetes are related to progressive damage to small caliber/microscopic blood vessels called capillaries. These complications include kidney damage (nephropathy), nerve damage, particularly in the feet and legs (neuropathy) and eye disease (diabetic retinopathy).
Diabetic retinopathy involves damage to the microscopic circulation of the retina which can lead to complications which threaten or damage vision. Diabetic retinopathy is the leading cause of vision loss in the U.S. in patients under age 55 and is second only to age-related macular degeneration (AMD) in Americans over 55. Fortunately, dramatic advances in the therapy of diabetic retinopathy have occurred in the last 25 years. As in the case of many diseases, early diagnosis and prompt treatment provide the best opportunity for optimal outcomes.
PHASES OF DIABETIC RETINOPATHY AND VISION-THREATENING COMPLICATIONS
For diagnostic purposes, diabetic retinopathy is divided into two phases – an earlier form called nonproliferative diabetic retinopathy (NPDR) and a more advanced form called proliferative diabetic retinopathy (PDR).
NONPROLIFERATIVE DIABETIC RETINOPATHY (NPDR)
Diabetic macular edema
The main problem associated with nonproliferative diabetic retinopathy is called diabetic macular edema. In this situation, capillaries in the macula (the central part of the retina, see Anatomy and Function of the Eye) which have been damaged by diabetes begin to leak fluid from the blood stream. Frequently, fatty materials called lipid exudates accumulate as well. The fluid leakage results in swelling of the tissue of the macula (imagine a sponge absorbing water). The medical term for swelling is edema, therefore this is called macular edema. There are many potential causes for macular edema, however that caused by diabetic retinopathy is called diabetic macular edema. As in any body tissue, swelling (edema) interferes with normal function. In the case of diabetic macular edema, vision becomes blurred. If swelling of the macula threatens or damages central vision, treatment is necessary to avoid progressive and potentially permanent loss of sight.
PROLIFERATIVE DIABETIC RETINOPATHY (PDR)
Proliferative diabetic retinopathy with extensive neovascularization and associated scar tissue formation.
Proliferative diabetic retinopathy with large area of neovascularization.
Proliferative diabetic retinopathy with vitreous hemorrhage overlying optic nerve
Proliferative diabetic retinopathy is characterized by gradual, progressive closure of the microscopic blood vessels which nourish the retina. Eventually, the available supply of oxygen and blood flow becomes inadequate for the needs of the retinal tissue. In an attempt to compensate for this lack of circulation, the body’s response involves the growth or proliferation of new blood vessels. Unfortunately, this response is detrimental since the new blood vessels which form do not grow where they are needed and are abnormal. Rather than growing within the retina itself and improving blood supply to the normal tissue, the new blood vessels (called neovascularization) grow on the surface of the optic nerve and/or the retina and in even more advanced cases, the iris. These new vessels are abnormal in that they are fragile and eventually tend to bleed into the vitreous gel (vitreous hemorrhage) causing floaters and blurred vision. With mild degrees of vitreous hemorrhage, a few floaters may be noted. With extensive hemorrhage, dramatic loss of vision can occur. Without proper treatment, scar tissue can also form in association with the abnormal blood vessels and can eventually result in tractional retinal detachment. In the worst case scenario, the process of proliferative diabetic retinopathy can result in severe loss of vision or even blindness.
EVALUATION OF DIABETIC RETINOPATHY
In addition to a thorough ophthalmic and vitreoretinal examination, additional diagnostic studies (see About Your Visit, Diagnostic Testing) are frequently necessary to evaluate and guide therapy for abnormalities associated with diabetic retinopathy. Testing may include retinal photography, fluorescein angiography, optical coherence tomography scanning and ocular ultrasonography.
TREATMENT OF DIABETIC RETINOPATHY
Significant advances in the treatment of diabetic retinopathy have occurred in recent years. With appropriate therapy, a substantial majority of patients can enjoy good outcomes with stabilization or improvement of vision. Realistic expectations are important however. Diabetes is a chronic disease and although very effective treatments are currently available both for diabetes and diabetic retinopathy, a cure is not possible. Any patient with diabetic retinopathy requires regular, periodic surveillance examinations. Additionally, an annual retinal screening examination is indicated for any diabetic patient even without a documented history of diabetic retinopathy.
In addition to specific treatments for complications of diabetic retinopathy, management of blood sugar and other associated medical conditions is critical in an effort to retard the development and/or slow the progression of diabetic retinopathy. Management coordinated through your primary care physician or endocrinologist should include:
- Controlling diabetes. Large clinical trials in the United States and the United Kingdom have conclusively demonstrated the benefits of good control of blood sugar. In the long term, this can have a significant beneficial effect on the course of diabetic retinopathy (as well as neuropathy and kidney disease).
- Controlling blood pressure. Hypertension can accelerate damage caused by diabetic retinopathy and should be properly managed.
- Controlling serum lipids. Many patients with diabetes may also have elevated serum lipids (triglycerides and cholesterol). As in the case of blood sugar and hypertension, control of these levels through diet, exercise and medication therapy can have a beneficial effect on the course of diabetic retinopathy.
- Cessation of smoking. Tobacco use can dramatically worsen the course of diabetic retinopathy as well as the other complications of diabetes. The risk for heart disease and stroke is also increased and therefore, smoking should be discontinued.
When necessary, your retinal specialist can provide a variety of sophisticated treatments for complications of diabetic retinopathy.
TREATMENT FOR DIABETIC MACULAR EDEMA
The mainstay of treatment for this condition is laser photocoagulation (see Surgical Procedures: Laser Photocoagulation). This technique involves the use of a powerful, precisely focused source of light to seal the microscopic leaking capillaries in the macula. In some cases, medication injection into the eye (intraocular injection of medication) may be recommended as well. The specific details of your abnormalities and management will be discussed by your physician at Northeast Wisconsin Retina Associates. The goal of therapy is to reduce or eliminate fluid leakage in the macula thereby controlling the swelling and stabilizing or improving vision.
TREATMENT FOR PROLIFERATIVE DIABETIC RETINOPATHY
The primary treatment for this abnormality is also laser photocoagulation. In this case however, a more extensive form of treatment called panretinal photocoagulation or scatter photocoagulation is performed (discussed in more detail in Surgical Procedures: Laser Photocoagulation). The therapeutic goal is to stop the growth of the abnormal blood vessels (neovascularization) and if possible, cause those which have already formed to undergo closure (termed regression). In many patients, adequate stabilization can be achieved following appropriate laser therapy. In some individuals however, repeated episodes of bleeding, progressive scar tissue formation or development of tractional retinal detachment may necessitate operative intervention. This involves a form of surgery called vitrectomy (detailed in Surgical Procedures, Vitreous Surgery).