Diabetic retinopathy

Definition
Diabetic retinopathy is an eye disease, associated as its name shows with diabetes. This is the main cause of decreased vision in people who suffer from diabetes. Retinopathy is related to all types of diabetes. If left untreated, diabetic retinopathy may cause blindness.

Causes
The probability of appearance of diabetic retinopathy directly correlates with the duration of the disease. Persistent high blood sugar causes damage to the smallest blood vessels in the retina (the area in the back of the eye that perceives the light signals, transforms them and sends them to the brain as nerve impulse in order to "see" what we see). Blood vessels gradually become thinner and this is a predisposition for thrombosis. Damaged vessels can also provoke bleeding or  fluid retention  in the retina. The condition is called edema of the retina.

The thrombosis of the small vessels in the retina results in reduced blood flow and oxygenation of the retina. The retina is from one side damaged by the hypoxia itself. From the other side this leads to the development of new pathological blood vessels (process known as neovascularization), which are fragile and may break down, forming a vicious circle.  

Risk factors
• Poor blood sugar control - not taking the prescribed antidiabetic drugs on a regular basis or not sticking up to your dietary regime may accelerate the appearance of retinopathy
• Duration of diabetes- the longer you have diabetes, the greater the chance to develop retinopathy
• Proteins in the urine
• Hypertension
• Pregnancy
• High cholesterol and/or triglycerides
• Smoking

Types
There are three basic types of diabetic retinopathy. They are non-proliferative retinopathy, maculopathy and proliferative retinopathy.

In the first type the wall of the blood vessels is damaged so that microaneurisms appear. They are visible as small red spots on the retina. They are very thin and are often the cause of retinal exudation, edema or bleeding. 

Maculopathy is the second type of retinopathy. It affects a specific area of the retina, near its center called macula lutea. The macula is responsible for the central vision as well as for the clear sharp vision. Nonproliferative retinopathy is usually combined with maculopathy as changes in the retina could not leave its elements, including the macula untouched.

Proliferative retinopathy is presented by thrombosis of the small retinal vessels and formation of new abnormal vessels that tend to bleed, cause exudation and edema. One of the most frequent complications of proliferative diabetic retinopathy is the detachment of the retina. This is an emergency, which, if left undiagnosed or untreated, may lead to complete blindness.  

Diagnosis
•To put the diagnose retinopathy the doctor will start by examination of the eye. This is done through a special microscope after dilatation of the pupils. During the test the doctor will look for deposits or blood in the retina, detachment of the retina, abnormal or new blood vessels
• To visualize better the blood vessels, your doctor may inject a special dye and follow its distribution within the vessels. In that way broken, dilated or leaking vessels could be identified. This test is known as fluorescein angiography.
• To examine the condition of the different layers of the retina, your doctor may recommend OCT- optical coherence tomography

Treatment
If the diabetic retinopathy is mild or moderate, good control of blood sugar levels may slow down the progression of the process. Otherwise, laser treatment is the main option for diabetic retinopathy.
Focal laser treatment is applied when leaking blood vessels need to be destroyed in order to stop their exudation. On the other hand scatter laser treatment is convenient for the neovascular retinopathy as it shrinks and destroys newly formed vessels

New type of therapy is yet available on the market. It is called Intravitreous anti-VEGF injection. The injections were firstly introduced for the treatment of senile macular degeneration. Additional studies have shown that they are also effective in patients with diabetic maculopathy. The VEGF is growth factor that promotes the formation of new vessels and its essential for their growth. Anti-VEGF drugs, by blocking VEGF, stop the neovascularization, characteristic for the proliferative diabetic retinopathy. For the moment this is not therapy of first choice, as its side effects are not fully explored. 

When the retinopathy is detected at an advanced stage or the laser treatment is not being effective, a surgical procedure called vitrectomy may be performed. It consist of removing the vitreous body (a jellylike substance situated between the iris and the retina, that supports the eye structures and determines the shape to the eye), when the same is being affected by retinal hemorrhage. The vitreous is than being replaced by synthetic analogues.

Conclusion
Although laser and surgical approaches in treating retinopathy exist, patients should be educated that neither of them is definitive. The bad control of their blood sugar levels may lead to recurrence of the retinopathy. That's why regular eye checks must be a part of the complex diabetes treatment.