Proliferative diabetic retinopathy

Proliferative diabetic retinopathy

Diabetes often causes damage to blood vessels, especially if blood sugar levels are not well controlled. Swelling, leakage, or blockage of the blood vessels in the eye cause a serious condition called proliferative diabetic retinopathy.

CAUSES OF DIABETIC RETINOPATHY

The retina is a light-sensitive tissue that lines the back of the eye. In your eye, the light rays that pass through the pupil are focused in the lens and penetrate the retina, where they are converted into signals that are transmitted by the optic nerve to the brain and interpreted as images. Therefore, it is as important to your vision as a processor is to a computer. Your retina has several delicate blood vessels that deliver oxygen and nutrients to maintain function.

Elevated blood sugar causes blood vessel walls to thin and red blood cells to clump together. These two processes lead to blood loss and vascular occlusion. The retina swells as blood leaks from vessels damaged by diabetes. When the blood vessels are blocked, the retinal cells in the area of ​​the blood vessel obstruction are deprived of oxygen and nutrition. A small, specialized area in the center of the retina, called the macula, is particularly sensitive to the consequences of vascular damage. Macula is important for clearly seeing the details of the objects in front of you. When the macula swells (a condition called macular edema), it causes blurred vision and impaired ability to recognize faces or read.

THE FOUR STAGES OF DIABETIC RETINOPATHY

proliferative diabetic retinopathy

The National Eye Institute (NEI) defines four different stages through which diabetic retinopathy can progress. These are mild, moderate and severe non-proliferative diabetic retinopathy and proliferative retinopathy. The first three stages of diabetic retinopathy are distinguished by the number of swollen, distorted, and blocked blood vessels in the retina. Macular edema can develop as early as the second stage of disease progression. In the third stage, the lack of oxygen and nutrients in the retina due to the vascular blockage triggers the secretion of a special molecule that stimulates the growth of new blood vessels. This molecule is called vascular endothelial growth factor, or VEGF for short. VEGF secretion promotes diabetic retinopathy to its most advanced, proliferative stage. It is characterized by the growth of new blood vessels in the retina, a process called neovascularization.

Proliferative retinopathy is particularly damaging to vision. The newly formed blood vessels are particularly fragile, and the blood that flows from them is absorbed by the retina into the vitreous gel, a jelly-like transparent substance in the eye through which light passes on its way from the lens to the retina. The accumulation of blood in the vitreous humor blocks vision partially, causing black “floaters” in your field of vision, or completely, resulting in blindness. Neovascularization of the retina can scar this delicate tissue and cause retinal detachment from the back of the eye. A detached retina cannot convert light rays into nerve signals, leading to partial or complete blindness.

SYMPTOMS OF RETINOPATHY

In summary, diabetic retinopathy can cause macular edema even in the early stages of development. In its advanced, proliferative stage, it leads to blood accumulation in the vitreous body (vitreous hemorrhage) and retinal scarring and detachment. Retinopathy usually develops in both eyes at the same time and causes the following symptoms:

• Blurred vision or changing from clear to blurred vision and back

• Floating and dark or black spots in the field of vision

• Poor night vision

• Changes in color perception, with colors appearing faded or washed out

DETECTION AND DIAGNOSIS OF DIABETIC RETINOPATHY

Diabetic retinopathy is diagnosed during a comprehensive eye exam. It may include the following tests, exams and procedures:

• Visual activity test. Eye chart reading measures your ability to see at different distances.

• Tonometry. A test that measures pressure in the eye.

• Funduscopy. It's a fancy name for an eye exam that's done with a magnifying glass. The drops applied to the surface of the eye dilate (dilate) the pupil, allowing the doctor to visually examine the “bottom of the eye,” including the retina, retinal vessels, and optic nerve. Fundoscopy detects changes in blood vessels (aneurysms), leaky blood vessels and fatty deposits, macular edema, as well as changes in the lens and optic nerve abnormalities.

• Optical coherence tomography (OCT). This test is similar to an ultrasound scan, but uses light instead of sound waves. OCT provides detailed images of eye tissue and complements visual inspection of the retina.

• Fluorescein angiogram. In this procedure, a fluorescent dye is injected into a vein in the arm. When the dye reaches the eye, multiple detailed images of the retina's blood vessels can be captured, revealing blood leaks and blood vessel changes that could not otherwise be detected.

The last two procedures are used when macular edema or progressive diabetic retinopathy is suspected.

TREATMENT OF DIABETIC RETINOPATHY

Many treatments for diabetic retinopathy aim to repair or remove the damaged blood vessels and restore blood flow to the retina. For best effect, two or more therapies can be combined

ANTI-VEGF INJECTION THERAPY

. VEGF, a vascular endothelial growth factor, is a key molecule that induces neovascularization and promotes the progression of diabetic retinopathy to its fourth stage, proliferative retinopathy. Drugs that counteract the effect of VEGF are injected into the vitreous body of the eye every month for six months. Thereafter, the frequency of injections is gradually reduced and treatment is completed within five years. Anti-VEGF drugs include Avastin (bevacizumab), Lucentis (ranibizumab), and Eylea (aflibercept). Avastin is approved by the US Food and Drug Administration (FDA) as a cancer drug, but is also used to treat eye diseases, including macular edema. Lucentis and Eylea are approved for the treatment of macular edema and diabetic retinopathy. Anti-VEGF therapy shows promise for the treatment of macular edema and proliferative diabetic retinopathy.

PANRETINAL LASER SURGERY

proliferative diabetic retinopathy

. This treatment is also known as scattered laser surgery or photocoagulation. Several thousand microscopic laser burns are performed to shrink the abnormal blood vessels. The burns are directed to the areas outside the macula to preserve central vision. Side effects of panretinal laser surgery include some loss of peripheral vision and defects in night and color vision caused by laser-induced damage to parts of the retina.

Vitrectomy. If proliferative retinopathy causes a buildup of blood in the center of the eye that blocks vision, the vitreous gel is surgically removed. In this procedure, the vitreous gel is removed by suction and replaced with sterile saline to maintain pressure in the eye and maintain the eye shape. Vitrectomy can be performed under local or general anesthesia; it often requires hospitalization and recovery takes several weeks. If both eyes require surgery, the second vitrectomy is performed after the first eye has completely healed.

When proliferative diabetic retinopathy is combined with macular edema, specific treatments for the latter can be combined with panretinal laser surgery and anti-VEGF therapy.

Injection or implantation of corticosteroids. Corticosteroids have antiangiogenic, antipermeability and antifibrotic properties. This means they prevent new blood vessels from growing, reduce fluid leakage into the retina, and prevent retinal scarring. Injections of steroids, usually triamcinolone, into the vitreous gel are performed as in anti-VEGF therapy. Implants are also inserted into the vitreous body and deliver a sustained amount of medication over a defined period of time. Some implants are designed for short-term treatment, such as Ozurdex (dexamethasone). Iluvien (fluocinolone acetonide) is used for longer treatment. Flexibility in choosing the steroid treatment regimen is essential as steroids are known to increase intraocular pressure and promote the development of glaucoma. Glaucoma is more common in diabetics than in the general population, so consider discussing the risks and benefits of steroid treatment with your doctor.

Focal/Raster Macular Laser Surgery. Unlike panretinal surgery, this treatment specifically targets the macula. 10-100 laser burns are inflicted to remove and seal the damaged blood vessels to prevent blood leakage and minimize macular swelling. This treatment can be combined with anti-VEGF therapy or used as a second line of defense if anti-VEGF therapy has proven ineffective.

OTHER DIABETES-RELATED OPHTHALMIC COMPLICATIONS

Although diabetic retinopathy is the most common and serious eye disease associated with diabetes, other complications such as glaucoma and cataracts are known to affect vision in diabetics.

Glaucoma is a disease in which the optic nerve is damaged and does not transmit signals from the retina to the brain. In most cases, glaucoma is caused by increased pressure in the eye. In diabetes, the growth of new blood vessels in the iris can block the flow of fluid in the eye. The pressure in the eye increases and a condition called neovascular glaucoma may develop. It is also known that people with diabetes are twice as likely as non-diabetics to develop a more common form of glaucoma, open-angle glaucoma. But the opposite is also the case: glaucoma patients have an increased risk of developing diabetes. Therefore, it is not clear whether high blood sugar levels cause open-angle glaucoma or whether the two diseases share some common risk factors.

Cataracts are a common cause of blindness due to clouding of the lens. The incidence of cataracts in diabetics is twice as high as in non-diabetics. This can be caused by chronic lens swelling caused by the constantly elevated blood sugar. Sudden, sharp changes in blood sugar concentration can also lead to distortion of the lens shape.

FINAL

Diabetes contributes to the development of serious eye diseases such as proliferative diabetic retinopathy, macular edema, glaucoma and cataracts. The best way to prevent diabetes-related blindness is to keep your blood sugar under control through a combination of diet, exercise, and medication. The incidence of developing diabetic retinopathy in diabetics whose hemoglobin A1c level is maintained below 7.0 is the same as in non-diabetics.

Eye diseases are easier to treat if they are detected in their early stages. Therefore, all diabetics should undergo a comprehensive eye exam at least once a year. Regular eye doctor visits ensure timely detection and treatment of diabetic retinopathy, glaucoma and cataracts.

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Inspired by Keith E. Barker