Diabetic Macular Edema (DME)
The occurrence of retinopathy in diabetic patients is a common cause of loss of vision. This happens when blood vessels in the patient’s eye are damaged in the retinal tissue. Sometimes these blood vessels will leak near the center of the retina (the macula), causing the area surrounding it to swell. This leads to excessive fluid leakage around the retina (edema), and the reduction or loss of central, detailed vision. Left untreated, it will cause blindness. Diabetic macular edema (DME) is a manifestation of Diabetic Retinopathy (DR) and is the most frequent cause of blindness in young and mid-aged adults.
What Is DME?
DME is a form or a subtype of diabetic retinopathy. In the retina, the small blood vessels are especially vulnerable to poor blood glucose control. When these vessels become damaged, the condition is known as diabetic retinopathy. DME occurs when these damaged blood vessels leak fluid and lipids onto the central macular area, the part of the eye where sharp, central vision occurs. This leads to swelling of the macula and can cause blurred vision or, in severe cases, profound vision loss.
Definition of DME: Macular Edema means swelling of the macula, the central area of the retina most critical for vision. It occurs when blood vessels leak fluid into the retina. The fluid build-up distorts the macula and causes blurring or distortion of vision.
DME can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses.
How is DME different from macular degeneration?
Macular degeneration is a condition of the eye that is often related to aging. It is commonly referred to as age-related macular degeneration, and is abbreviated as AMD. It is the most common cause of irreversible blindness in people over the age of 65. It is a slow progressive disease that affects the central area of the retina called the macula. This is the location of the retina responsible for central vision or the vision which gives us the greatest detail in our sight. While there is a higher incidence of macular degeneration with hypertension, arteriosclerotic vascular disease and diabetes, it is not exclusive to diabetic people and commonly occurs over the age of 65 years. The macular degeneration occurring in people with diabetes, results from leakage of small blood vessels, which leads to fluid accumulation under the retina and loss of central vision.
DME, on the other hand, is specifically a disease of people with diabetes. It is estimated that approximately 30 percent of people living with diabetes for 20 or more years will develop DME. As mentioned above, DME is a form of diabetic retinopathy. In the retina, the small blood vessels are especially vulnerable to poor blood glucose control. When these vessels become damaged, the condition is known as diabetic retinopathy. DME occurs when these damaged blood vessels leak fluid and lipids onto the central macular area, the part of the eye where sharp, central vision occurs. This leads to swelling of the macula and can cause blurred vision or, in severe cases, profound vision loss. DME can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses.
How do hypoxia and the production of vascular endothelial growth factor play a part in DME?
Diabetic macular edema (DME) occurs when the damaged blood vessels from diabetic retinopathy leak fluid and lipids onto the central macular area.
Vascular Endothelial Growth Factor (VEGF) is created basally in response to ischemia or hypoxia. Hypoxia or ischemia can be defined as low or absent oxygen supply to a tissue and the retinal hypoxia has been implicated in the development of DME. This hypoxia causes increased expression of vascular endothelial growth factor (VEGF), which increases blood vessels’ permeability that has been shown to cause leakage from retinal vessels. Practically speaking, any time you touch the eye (laser, cataract surgery, inflammation) you release VEGF and this VEGF, in turn, causes increases leakage of the fluid on the central macula, giving rise to DME.
Treatment & correction of DME
If left untreated, swelling in the macula can cause vision problems that get worse over time or become permanent. The swelling of Cystoid Macular Edema can often be reduced or eliminated with anti-inflammatory eye drops or intraocular injections. Sometimes oral anti-inflammatory medicines are also prescribed. The swelling of Diabetic Macular Edema is often treated with laser light treatments that can help to “dry-up” leaky blood vessels in the back of the eye. Commonly, when a patient develops DME, ophthalmologists typically intervene with photocoagulation to slow vision loss. Photocoagulation also remains the principal treatment for DME and has been found to substantially reduce the risk of vision loss, increase the chance of visual improvement, and decrease the frequency of persistent macular edema.
New pharmacologic agents, such as protein kinase C ?(PKC) inhibitors and vascular endothelial growth factor (VEGF) inhibitors, are currently being studied in clinical trials and have shown evidence of benefit with regards to visual outcomes. In addition, Intravitreal steroid use is also widely gaining acceptance as a treatment for DME. Corticosteroids also down regulate the production of VEGF.
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