The Problem
When you have diabetes, high levels of sugar in your blood affect the blood vessels in the retina. These damages vessels can lead to vision problems.
Diabetes affects the retina, the light sensitive tissue at the back of the eye, in two ways: Diabetic Macular Edema (DME) and Diabetic Retinopathy. They are described below.
1. Diabetic Macular Edema (DME)
Diabetic macular edema (DME) is a complication of diabetic retinopathy that specifically affects the macula, the central part of the retina responsible for detailed vision. When someone has diabetes, high levels of sugar in the blood can damage the tiny blood vessels in the retina. Aneurysm type changes can occur in the blood vessels around the central vision. These aneurysms can cause fluid and protein to leak into the macula, leading to swelling and thickening—this condition is known as diabetic macular edema.
The macula is crucial for clear and sharp vision, allowing you to see fine details, read, and recognize faces. When it's affected by edema, your central vision may become blurred or distorted. You might notice difficulty in seeing details, straight lines might appear wavy, or you might experience dark or empty spots in your central vision.
Our goal is to decrease leakage so that vision can be improved or at least maintained. Chronic leakage in the center vision is thought to decrease vision more so over time.
2. Diabetic Retinopathy
In diabetes, the retina can sometimes receive poor blood flow. When that happens changes can be seen. The first changes are classified as Non-Proliferative Diabetic Retinopathy. What that means is that changes are seen but no “proliferation” or new blood vessels are growing. Typically, hemorrhages are seen in the retina. These changes are monitored for progression over time.
Proliferative diabetic retinopathy is a more advanced stage, where new abnormal blood vessels grow on the surface of the retina, which can bleed and cause vision loss. Although it seems like a great idea that new blood vessels are growing in the eye when there is a lack of blood flow, the problem is that they always grow in the wrong places. These blood vessels are also thin and weak which can lead to breakage, leaving the eye full of blood.
The Procedure
Treatment of Diabetic Macular Edema:
There are two methods to decrease the leakage to help improve or preserve vision. They are injections with drugs that decrease leakage, and laser to the aneurysms that cause the leakage. These drugs are termed anti-Vascular Endothelial Growth Factor or Anti-VEGF drugs. When the leakage is too close to the center it is not safe to be lasered and so anti-VEGF drugs are injected into the eye to decrease the leakage.
If the aneurysms are far from the central vision, they can be lasered to decrease leakage. Sometimes even when laser is planned, anti-VEGF drugs are injected to decrease the leakage so that the laser can be better absorbed by the leaking aneurysms.
Treatment of Proliferative Diabetic Retinopathy:
When we see Proliferative Diabetic Retinopathy, or new blood vessels growing in the eye, treatment is indicated. We often treat the eye with injections of anti-VEGF drugs, which help to decrease new bleeding by shrinking these new blood vessels. If this keeps happening, then we can add laser to the retina to help prevent frequent recurrences of bleeding into the eye. If the blood does not clear, we can do surgery to help clear the hemorrhage.
Sometimes new blood vessels can pull on the retina causing a tractional retinal detachment. Depending on where this occurs, we may need to proceed with surgery.
Risks?
Risk of Anti-VEGF injections:
The main risk is 1 in 5,000 of bleeding, infection, or retinal detachment. The eye can feel itchy or scratchy on the day of the injection; this usually improves by the following day. The eye is frozen, so most people do not feel the treatment. After the treatment, Dr. Adatia suggests using preservative free artificial tears every 15 minutes for 2 hours. The reason for this is that, as the eye is frozen, we do not blink normally, and the eye can get dry and painful from decreased blinking. Using the drops help prevent that and often people will remain comfortable even on the day of treatment.
If there is persistent pain and decreased vision that does not improve on the following day, Dr. Adatia would like to see you back right away. Often this is just from a scratch or an abrasion on the cornea or front of the eye. However, infection would need to be ruled out. If pain and decreased vision persists and does not improve the next day, please call in to see Dr. Adatia. If it is an evening or a weekend, patients are advised to go to the Rockyview Emergency Department in Calgary.
Otherwise, the white of the eye can be red if there is a small bruise around the injection site. Like a bruise, this typically changes color and goes away on its own over the next few weeks.
At the time of the injection, you may notice floating material; that is the medication, and it should disperse over hours.
In general, this is a very safe and common procedure.
Risk of Focal (Central) Laser for Diabetic Macular Edema:
The laser is only done away from the center. This minimizes the risk to central vision. There is the risk that laser scars can expand over time and cause areas of vision to be lost around the central vision. Again, in modern practice this is minimized as laser is away from the center and the spot sizes are small.
Risk of Peripheral Laser for Proliferative Diabetic Retinopathy:
Peripheral laser destroys dying retina to prevent a hormone, vascular endothelial growth factor (VEGF) which is released by the dying retina, from causing new blood vessel growth. These new blood vessels are prone to bleeding into the eye. If done too aggressively, it can damage peripheral vision. Dr. Adatia does a fluorescein dye test to determine which areas of the retina have poor circulation to specifically target those areas to minimize any peripheral vision loss.