Diabetes Mellitus and The Eye

Insulin, a hormone manufactured by the islet cells in the Pancreas, is critical to good health. Insulin doesn?t dissolve glucose; rather, it moves glucose (simple sugar) out of the bloodstream and into the cells in muscle and the liver, where it is converted into glycogen, an energy storage molecule. There are two forms of Diabetes, which adversely affect the action of Insulin: [caption id="attachment_269" align="alignleft" width="231"] Home glucose testing is critical for control.[/caption] Type I, or Insulin Dependent Diabetes Mellitus: 80% of these cases are in children with no family history. Believed to be viral in origin or possibly related to not enough exposure to bacterial antigens due to an overly sterile childhood, the pancreas in Type I Diabetes mellitus makes very little or no insulin. Insulin Dependent Diabetes mellitus requires insulin be brought in externally to the body, either via periodic injections, an insulin pump, or inhalation. And it is not only high glucose levels that can be dangerous in Type I diabetics. Diabetic ketoacidosis can occur. This is a life-threatening condition that develops when cells in the body are unable to get the sugar (glucose) they need for energy. ?When the cells do not receive sugar, the body begins to break down fat and muscle for energy. If this happens, ketones, or?fatty acids, are produced and enter the bloodstream, causing a chemical imbalance called diabetic ketoacidosis (DKA). ?Although more common in Type I diabetics, it can also occur less commonly in uncontrolled Type II diabetes, described below. Type II or Non-Insulin Dependent Diabetes mellitus occurs most commonly in adults with a family history of the disease, obesity, or both. Unlike Type I Diabetes mellitus, Type II Diabetes can usually be controlled with oral medications and diet. Although metabolic acidosis is not usually a complication of Type II Diabetes, glucose levels can be much higher, especially on initial diagnosis. It is not unusual to have glucose levels of several hundred milligrams per deciliter (normal glucose levels are 70-120 mg/dl). Both Type I and Type II Diabetes mellitus can damage the eye, particularly if glucose is routinely uncontrolled.? The most common complications that can occur are cataracts and diabetic retinopathy. Less common are traction retinal detachments and neovascular glaucoma. What is Diabetic Retinopathy? Diabetes, when uncontrolled, damages the delicate inner lining of the smallest arteries and capillaries (blood vessels) in the body. These small blood vessels are found in the distal extremities (toes), kidney, heart and eyes. In the early stages of diabetic retinopathy, the small blood vessels become weak, forming tiny balloons along their walls called microaneuryms. Later, the weak blood vessels can weaken further, leaking plasma, protein and blood which can dramatically worsen central vision.? This early stage is known as Background Diabetic Retinopathy. Treatment for Background Diabetic retinopathy is performed using laser cauterization if the leaks are threatening or reducing central vision, and sometime injection of steroids or Anti-VEGF inhibitors into the vitreous gel if the leaks are unresponsive to laser or are too close to the center of the retina to treat. Diagnosis of diabetic retinopathy is best performed by an ophthalmologist (M.D.) or optometrist (O.D.) using direct visualization, optical coherence tomography (OCT) or fluorescein angiography. [caption id="attachment_267" align="alignright" width="255"] Diabetic retina as seen using Fluorescein Angiography[/caption] Fluorescein angiography is a simple and highly informative test. A water soluble dye is injected into a vein in one of the patient?s arms. The dye circulates everywhere, including into the eye. A precise microscopic camera creates a flash using a blue filter. This excites the dye, which causes it to glow green. Photographs are then taken of the green-glowing dye as it circulates throughout the retina. If there is a small leak from a tiny blood vessel, it will be readily seen and can then be treated accurately using laser by the eye doctor. Background diabetic retinopathy does not occur immediately, but rather 5-10 years after the onset of disease, if the glucose levels fail to be controlled. Damage to the small blood vessels is permanent; therefore it is not uncommon to require repeated laser treatments over several years once background diabetic retinopathy has begun. Proliferative Diabetic Retinopathy (PDR) The more aggressive form of diabetic retinopathy is the proliferative form.? This occurs due to the tiny blood vessels closing off, creating small areas of the retina that are not obtaining enough oxygen. In response, there is formation of abnormal new and very fragile blood vessels, which is called neovascular growth. Rather than being helpful in bringing oxygen to the retina, these neovascular vessels form a disorganized tangle that not only leak large amounts of blood and plasma, but can contract, lifting off the retina and creating a traction retinal detachment. Treatment of PDR is aimed at reducing the oxygen need of the non-critical areas of the retina using hundreds of peripheral laser burns (PRP, or pan-retinal photocoagulation) and in reducing the chemical signal to form these blood vessels by injecting Avastin or Lucentis into the vitreous gel. [caption id="attachment_268" align="alignleft" width="244"] Proliferative Diabetic Retinopathy[/caption] In advanced cases of proliferative diabetic retinopathy, a retinal surgeon may my required to evacuate blood inside the vitreous or to repair the traction retinal detachment. In Summary Because the consequences of diabetic retinopathy are so severe if the disease remains uncontrolled, it is my recommendation that you take the following measures if you have diabetes mellitus: 1.? Obtain Hemoglobin A1c levels every three months. This tracks your overall glucose control. Non-diabetics have Hemoglobin A1c levels less than 6%. The American Diabetes Association recommends a Hemoglobin A1c level of less than 7%, while the American Association of Clinical Endocrinologists recommends a level of less than 6.5%. The following table is instructive in correlating Hemoglobin A1c levels with average glucose levels: A1c(%) ??? Mean blood sugar (mg/dl) 6 ??? ??? ??? 135 7 ??? ??? ??? 170 8 ??? ??? ??? 205 9 ??? ??? ??? 240 10 ??? ??? ??? 275 11 ??? ??? ??? 310 12 ??? ??? ??? 345 2. Watch Your Diet and Your Weight The percentage of Americans who are obese, as measured by Body Mass Index (BMI) is over 30%. Twenty years ago it was only 18%. This is a direct effect of our changing diet, and not just the convenience of fast food, but additionally the preponderance of processed carbohydrates and high caloric fat products that populate the grocery store aisles. David Kessler, the former head of the Food and Drug Administration has written a book entitled, The End of Overeating: Taking Control of the Insatiable American Appetite. His premise is that the food scientists that work for the companies that manufacture processed and cooked foods have mastered the science of combining fat, sugar and salt into a concoction that creates food cravings with resultant overeating. Do what I did to lose 30 pounds ? join Weight Watchers and do most of your shopping along the perimeter of the grocery stores where the food scientists can hurt you ? fish, chicken, skim milk, fruits and vegetables and fat free cheeses. 3. See an endocrinologist Primary doctors cannot be entirely blamed for wanting to care for your every illness. But if your Hemoglobin A1c is more than 6.5%, you need to gently suggest to him or her that it is time to put the treatment of your diabetes in the hands of a good endocrinologist. Diabetes mellitus is the bread-and-butter illness for endocrinologists. They will help you to reign in your diet, instruct you when and how many times to measure your blood sugar, and are more likely to be obsessive about following your laboratory results and less inhibited about telling you when you?re not doing as well as you could. A good endocrinologist takes a personal interest in your diabetes control and administers ?tough love.? 4. Get regular eye examinations If you do not yet have diabetic retinopathy, examinations should be performed annually at least. If you do have diabetic retinopathy, examinations and treatments can range between every month to every six months. Seek an ophthalmologist or optometrist who sees a lot of diabetics and performs? Optical Coherence Tomography, Digital Retinal Photography and Fluorescein Angiograms, since these are frequent diagnostic tests required for this condition. If you have questions about your own eye health, why not post them for me on our new "Ask The Eye Doctor" form at VisiVite.com? -- Paul Krawitz, M.D., President VisiVite.Com