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Diabetic Retinopathy



 
Diabetic Retinopathy
Diabetic retinopathy is the leading cause of acquired blindness among Americans under the age of 65. The great majority of this blindness can be prevented with proper examination and treatment by ophthalmologists (EyeMDs). An extraordinary amount of research has already been completed, and is relied upon heavily by practicing ophthalmologists, in the treatment of patients with diabetes. Unfortunately, patients who are not properly referred for evaluation and management or those who, for any reason, fail to get proper care from an ophthalmologist, are at the greatest risk of vision loss. Ophthalmologists primarily rely on the results of four major clinical studies to guide their treatment of patients with diabetes mellitus. These are the Diabetes Control and Complications Trial (DCCT), the Diabetic Retinopathy Study (DRS), the Early Treatment Diabetic Retinopathy Study (ETDRS), and the Diabetic Retinopathy Vitrectomy Study (DRVS).

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Background Diabetic Retinopathy
Background diabetic retinopathy (BDR) may occur at any point in time after the onset of diabetes. In general, this is the first "stage" of diabetic retinopathy and, therefore, the least concerning. This condition is often present without any visual symptoms. Findings in the retina include dot and blot hemorrhages (tiny hemorrhages in the retina itself), microaneurysms (out-pouchings of capillaries), and exudates (retinal deposits occurring as a result of leaky vessels). The development of this condition in type I (juvenile-onset) diabetics is rarely present prior to three or four years following the onset of diabetes. In type II (adult-onset) diabetics, background diabetic retinopathy may be present at the time of diagnosis of the condition. Primary care practitioners should refer patients with diabetes to ophthalmologists, accordingly.

In general, patients are not typically treated with laser photocoagulation of the retina for background retinopathy. An exception exists for some patients with an advanced form of BDR known as pre-proliferative diabetic retinopathy. Ophthalmologists may recommend treatment at this stage, especially if the opposite eye has had diabetic related complications.

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Clinically Significant Macular Edema
Clinically significant macular edema (CSME) is a condition of swelling of the macula related to the development of leaky capillaries and microaneurysms. This condition may or may not be associated with reduced or distorted vision. Ophthalmologists use rather strict criteria to determine whether a patient should be treated with focal laser photocoagulation for this condition. These criteria were set forth by the studies mentioned above.

Patients with CSME are generally recommended to undergo focal laser photocoagulation. This entails a fluorescein angiogram to guide treatment and utilization of a laser to help "dry up" the localized swelling (macular edema). Ophthalmologists apply laser treatment to the macula of the eye, avoiding the fovea where central acuity resides, in a grid-pattern or directly to leaking microaneurysms. The risk of visual loss is reduced by more than 50% for patients with CSME who undergo focal laser photocoagulation. Even patients with 20/20 vision who meet guidelines for treatment should be considered for laser therapy to prevent eventual visual loss. It is important to realize that laser treatment does not usually improve vision, but is aimed at prevention of further visual loss. Most patients with CSME require 3 to 4 different focal laser sessions, two to four months apart, to resolve the swelling.

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Proliferative Diabetic Retinopathy
Proliferative diabetic retinopathy (PDR) carries the greatest risk of visual loss of the conditions discussed thus far. The condition is characterized by the development of neovascularization (new, abnormal vessel growth) on or adjacent to the optic nerve and vitreous or pre-retinal hemorrhage (hemorrhage in the vitreous humor or in front of the retina). PDR usually occurs in eyes with advanced background diabetic retinopathy and is thought to be secondary to ischemia (lack of oxygen or blood flow) of the retina. It has been theorized that a "neovascular growth factor," acting as a local hormone, may cause the development of neovascularization. Unfortunately, the neovascular vessels are abnormal and have a tendency to break and bleed into the vitreous humor of the eye. In addition to sudden vision loss, this may lead to more permanent complications, such as tractional retinal detachment and neovascular glaucoma.

Patients with PDR should receive scatter laser photocoagulation (laser treatment of the ischemic peripheral retina) as soon as possible following diagnosis of the condition. This treatment is also known as pan-retinal laser photocoagulation. By causing regression of the neovascular tissues, the risk of severe vision loss is substantially reduced. Scatter laser photocoagulation (also known as PRP, or pan-retinal photocoagulation) is an in-office or out-patient procedure done with or without an anesthetic injection adjacent to the eye. Many patients will experience mild discomfort with the laser treatment, although this can be resolved with an anesthetic block. The laser treatment usually takes less than 30 to 45 minutes per session. A complete laser treatment, however, may require up to 3 or 4 different sessions, with a total of one to two thousand laser applications ("spots").

In some patients with PDR, the vitreous hemorrhage prevents the ophthalmologist from performing the laser treatment. Simply put, the blood is in the way of the laser beam. If the vitreous hemorrhage fails to clear within a few weeks or months, a vitrectomy surgery may be performed to mechanically clear the hemorrhage and laser photocoagulation is then applied, either at the time of the vitrectomy or shortly thereafter. Patients who have tractional retinal detachment are usually scheduled for vitrectomy surgery promptly.

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