Friday, October 21, 2011

Diabetic retinopathy treatments

Diabetes mellitus is a fast growing health hazard throughout the world. According to a study Hyderabad has emerged as the Indian metro city with the highest incidence of diabetes. The study estimated 16.6% of Hyderabad populations have diabetes making it diabetic capital of India. A recent survey revealed only one third of the diabetic individuals know the evil effects of diabetes on the eye.

Diabetes is a metabolic disorder characterized mainly by high blood sugar. It can affect different parts of the body including blood vessels, heart, kidney, eye, foot and nerves.

Diabetic retinopathy is due to damage to the small blood vessels present in the retina (innermost light sensing tissue of the eye). Poorly maintained blood sugar levels and duration of diabetes are the risk factors for the progression of diabetic retinopathy.

Most diabetic patients are non insulin dependent (NIDDM or type 2 diabetics) and usually control their blood sugar with exercise and oral medication. The remaining are insulin dependent (IDDM or type 1 diabetics) and require insulin to regulate the sugar levels.

Diabetic retinopathy is seen in both type 1 and type2 diabetes. The risk is increased when hypertension, renal disease and pregnancy are added. Regular eye checkups (as diabetic retinopathy is asymptomatic unless the macula is involved) with added laser when necessary significantly stabilizes the progression of retinopathy.

Diabetic retinopathy is divided into 3 main categories
   1.. Non proliferative diabetic retinopathy
   1. Proliferative diabetic retinopathy
   1. Diabetic maculopathy

Ocular Symptoms of Diabeties:
In early stages diabetic retinopathy is asymptomatic; there may be a frequent change in glass power due to uncontrolled diabetes; that is why it is recommended that yearly checkup is necessary. First checkup in advisable at the time of diagnosis in type II diabetes and by 5 years in case of type I diabetes.

Signs of Nonproliferative Diabetic Retinopathy diabetic retinopathy:
1. Microaneurysums: These are deep red dots seen as first visible sign of diabetic retinopathy.
2. Retinal hemorrhages, which may be superficial known as flame shaped hemorrhages or deep hemorrhage known as dot and blot hemorrhages.
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3. Retinal lipid exudates also known as hard exudates which are lipid deposits that are associated with leakage from vessels.
4. Cotton-wool spots, also called soft exudates or nerve fiber infarcts, result from local ischemia and the subsequent swelling of the nerve fibers which gives cotton-wool spots their characteristic white fluffy appearance.
5. Intra Retinal Micro vascular Abnormalities (IRMAs) are dilated capillaries, which seem to function as collateral channels.
6. Venous beading and Venous loops are important sign of sluggish retinal circulation which are seen advanced non proliferative diabetic retinopathy.
7. Macular edema or retinal thickening is an important manifestation of NPDR and represents the leading cause of decreased vision in diabetics. The intercellular fluid comes from leaking microaneurysms or from diffuse capillary incompetence and is often accompanied by retinal hard exudates. Most patients with hard exudates have increased cholesterol levels. Good control of blood sugar levels and cholesterol decreases the chance of hard exudates formation.
8. The hallmark of proliferative diabetic retinopathy is presence of neovascularization (New blood Vessels) which may be neovascularization of disc (NVD) or neovascularization elsewhere (NVE). Decrease in vision occurs either due to bleeding from this new vessels or due to development of tractional retinal detachment due to contraction of the fibrovascular component in these new blood vessels

Treatment of diabetic retinopathy
   1. Systemic disease control
      Medical treatment of diabetes, hypertension, anemia and renal disease are important to slow the development and progression of diabetic retinopathy.
   2. Laser treatment
      Laser treatment is indicated in maculopathy and proliferative diabetic retinopathy. It is an outpatient procedure and requires the pupil to be dilated to the full extent. Laser light is focused on the retina with the help of a contact lens, after anaesthetizing the eye with topical eye drops.

Laser for macular oedema: The goal in treating macular oedema in diabetic retinopathy is not to improve the vision but to stabilize vision by attempting to stop the damaged blood vessels from leaking fluid into the retina. Small discrete areas of vessel leakage re treated with focal lasers and diffuse leakage is treated with a grid pattern. Vision may get little worse following laser for a short period. Most of the patients who receive laser for macular oedema maintain better vision than those who had not received any treatment.

Laser for proliferative diabetic retinopathy: PRP or pan retinal photocoagulation is done to treat the abnormal new vessels. Peripheral retina which is not receiving adequate blood flow is treated by laser to halt the new vessel formation. This process requires over 1000 laser applications and hence is divided into three or more separate sessions. The laser helps to prevent severe visual loss occurring due to complications of diabetic retinopathy, though it does not improve the lost vision.

Intraocular steroids and other medications:
Diffuse macular oedema and focal oedema not responding to laser treatment require intraocular injection of steroids or avastin (bevacizumab). Studies with avastin showed promising results with excellent safety profile. The drug lasts for about 6 weeks in the eye after a single injection and may need to be repeated if the disease reactivates.

Surgery: A person may have bleeding before the application of laser or rarely the diabetic retinopathy progresses even after laser treatment. Majority of vitreous hemorrhage clears by six weeks by absorption of the body. Vitrectomy surgery is indicated to remove vitreous hemorrhage if it is not absorbed within 6 weeks. The procedure is also done for treatment of tractional retinal detachment which threatens or involves macula.

Vitrectomy is performed in the operating room after anaesthetizing the eye with local anesthetics. It is one to two hours procedure and the patient can go home the same day.

Risk factors for progression of diabetic retinopathy:
   1. Duration of diabetes
   2. Glycemic control ( blood sugar control)Hypertension
   3. Hyper lipidemia ( increased blood cholesterol)

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