Diabetes is a disorder of sugar utilization and storage which causes damage to blood vessels throughout the body. When the blood vessels in the eye are effected it is called Diabetic Retinopathy. Diabetic retinopathy is the leading cause of blindness in patients 20 to 74 years of age. There are two stages of diabetic retinopathy: nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR). Neovascular glaucoma is a less common complication of diabetes, and will also be discussed.
Nonproliferative Diabetic Retinopathy (NPDR)
In NPDR, the retinal blood vessels which are normally watertight begin to leak. This causes blood, serum, and lipid to collect in the retina. If the leakage is excessive, fluid builds up in the retina, causing it to swell. This is called Macular Edema. Serum and lipid which leak may cause the formation of solid deposits in the retina called exudate.
A patient with macular edema may not have any visual symptoms. However, if the swelling involves the central macula, vision will become blurred, distorted or darkened.
Evaluation of NPDR
In addition to frequent thorough eye exams,Optical Coherence Tomography (OCT) may be used to detect macular edema. OCT is a scanning laser which images a slice of the retina in cross section. Fluorescein Angiography is a test in which a dye is injected into a vein in the arm. Special photographs are taken of the retina as the dye passes through the blood vessels in the eye. The abnormal blood vessels leak the injected dye and become detectable to the physician.
Proliferative Diabetic Retinopathy (PDR)
Proliferative diabetic retinopathy is the more advanced form of diabetic retinopathy. In PDR abnormal blood vessels begin to grow from the surface of the retina into the vitreous gel. This is called neovascularization. The abnormal vessels can break and bleed into the vitreous cavity, causing a Vitreous Hemorrhage. Symptoms of a vitreous hemorrhage usually include the appearance of spots, strands, or a curtain in the vision. The abnormal blood vessels may also cause scar tissue to form. Scar tissue can block light from reaching the retina, or pull on the retina causing a Traction Retinal Detachment. Either of these problems may lead to severe visual loss. A person with PDR can also have macular edema, as in NPDR.
PDR can also lead to Neovascular Glaucoma , a condition in which abnormal blood vessels grow on the iris or colored part of the front of the eye. These abnormal blood vessels can block the flow of fluid from the eye and cause the eye pressure to become very high. Neovascular glaucoma can cause pain, halos around lights, and rapid loss of vision.
The Patient’s role in Diabetic Retinopathy
The best treatment of diabetic retinopathy is prevention. Good control of blood sugar, blood pressure, and cholesterol will significantly reduce the risk of vision loss. It is recommended that patients take an active role in managing blood sugar and try to keep Hemoglobin A1C levels as low as possible, optimally 7 or less. A close relationship between patient and primary care physician is vital to preserve eyesight and overall health.
It is important to realize that diabetes may damage the retina without causing any noticeable visual symptoms. For this reason, individuals with diabetes should receive dilated eye exams regularly. With proper screening, follow-up and treatment, the majority of patients with diabetic retinopathy maintain useful vision and avoid severe visual loss.
Treatments for Diabetic Retinopathy
Treatment of NPDR
When macular edema effects or threatens vision, treatment is typically recommended.
Laser treatment for macular edema is a painless in-office procedure. Laser light is applied to the areas of leakage. The goal of laser treatment is to decrease the swelling by diminishing the leakage, and therefore, stop the loss of vision. Most, but not all, patients show a beneficial response to laser treatment. In some patients multiple laser treatments are required. Even when laser treatment successfully seals the leaking vessels, new areas of leakage may arise later.
Intraviteal Drug Therapy may be recommended to treat macular edema. The goal of these injections is to make the retinal vessels less leaky. These injections are very effective and can improve vision in many cases. In some patients with diabetic macular edema, a series of intraocular injections over a long period of time (sometimes years) is the most effective way of managing diabetic macular edema.
Vitrectomy Surgery is effective at treating diabetic macular edema. During vitrectomy, the vitreous gel is removed. Fibrous membranes on the surface of the macula are removed with microscopic forceps. Most patients experience decrease in macular edema and improvement in vision.
Treatment of PDR
Laser Treatment is the first line of treatment for PDR. Unlike limited focal laser for macular edema, PDR requires a more global treatment. This is called Pan-Retinal Photocoagulation (PRP). PRP treats the peripheral retina and causes abnormal blood vessels to shrink. Although PRP can sometimes reduce night or side vision, it decreases the likelihood of bleeding, and can reduce the risk of severe visual loss by up to 50%. PRP laser is an in-office procedure and is often carried out over several sessions.
Vitrectomy Surgery may be indicated in patients who develop vitreous hemorrhage or tractional retinal detachment. During vitrectomy, the vitreous gel and blood is removed. Microscopic forceps are used to remove scar tissue. Bleeding blood vessels are cauterized or treated directly with laser.
Vitrectomy surgery is an outpatient procedure performed at the surgery center under local anesthesia. Most patients experience improvement in vision and eye health following vitrectomy.