Avast majority of persons above the age of forty living in Guyana suffer from some form of elevated blood sugar or Diabetes Mellitus. Additionally, a fraction of these have poor control over it which leads to a number of issues, one being diseases affecting the eye and vision.
Diabetic eye disease is actually a group of conditions resulting from symptoms of diabetes. These can take two major forms:
1. Diabetic retinopathy – which affects blood vessels in the retina (the light-sensitive area that lines the back of the eye). It is the premier underlying cause of visual impairment and blindness in adults suffering from diabetes.
2. Diabetic macular edema or DME – this is a consequence of diabetic retinopathy and is basically swelling in an area of the retina called the macula. Diabetic eye disease also includes cataract and glaucoma.
What exactly causes diabetic retinopathy?
When blood sugar is chronically high from diabetes mellitus, there is widespread damage to the tiny blood vessels in the body, including the retina, leading to what is known as diabetic retinopathy.
The retina works in the capacity to detect light and to convert it to nervous impulses that are sent via the optic nerve to the brain. Diabetic retinopathy can lead to blood vessels in the retina leaking fluid or bleeding after blood vessel destruction, thus enhancing the distortion of vision. When in the advanced stages, new abnormal blood vessels grow back and increase in number on the retina’s surface.
This leads to scarring and cell loss and thus further vision loss. It goes through four stages:
• Mild non-proliferative retinopathy – This occurs when small areas in the blood vessels in the retina begin to swell and may leak fluid into the retina.
• Moderate non-proliferative retinopathy – As there is progression, there is also swelling and distortion of the blood vessels that bring nutrients to the cells of the retina. This loss in the ability to transport blood causes a characteristic change in the appearance of the retina and can lead to DME.
• Severe non-proliferative retinopathy – The progression leads to many more blood vessels being blocked, preventing blood from reaching certain areas of the retina. These specific areas compensate for this loss by secreting compounds known as growth factors that stimulate the retina to grow new blood vessels.
• Proliferative diabetic retinopathy (PDR) – At this stage, the growth factors secreted by the retina triggers the growth and multiplication of new blood vessels, which grow along the inside surface of the retina and into the vitreous gel, which is the fluid that fills the eye and gives it its shape. These new blood vessels are very fragile and are more likely to break and bleed. Scar tissue that has developed can contract and cause retinal detachment. This leads to permanent vision loss.
What is Diabetic Macular Edema (DME)?
DME occurs when there is a build-up of fluid in a part of the retina known as the macula. What makes the macula so important is the fact that it is necessary for the sharp, straight-ahead vision that is used for reading, facial recognition and driving.
A little-known fact is that DME is the most common cause of vision loss among people with diabetic retinopathy. Also, approximately half of all people with diabetic retinopathy will develop DME. It also occurs at any stage but is more prominent in the latter stages.
What are the risk factors?
• Diagnosis of either type 1 or type 2 diabetes
• Diagnosis of diabetes at an earlier age
• Females are at a higher risk than males
• Age 40 and above
What are the symptoms of diabetic retinopathy and DME?
The early stages of diabetic retinopathy are usually asymptomatic, notwithstanding symptoms of diabetes and some small amount of blurred vision that occurs on and off and is often confused as being normal eye shifts.
The illness usually gets worse and is not noticed until vision is constantly affected. Due to bleeding of the retinal vessels, persons may complain of seeing numerous floating spots in their visual fields. These may dissipate, but if not treated there is always a recurrence, thus increasing the risk of blindness. If DME simultaneously occurs, it can lead to blurred vision.
How are diabetic retinopathy and DME detected?
The diagnosis of these two diseases must actually be done using a comprehensive dilated eye exam that includes each of the following components:
1. Visual acuity testing – This is the eye chart test that measures how well a person sees at different distances.
2. Tonometry – This test is done to measure the pressure inside of the eye.
3. Pupil dilation – When a specific type of drop is placed on the eye’s surface, it causes the pupils to widen, thus allowing a doctor to look at the retina and the optic nerve.
4. Optical coherence tomography (OCT) – As complex as the name sounds, the technique used is very similar to ultrasound, but uses light waves instead of sound to capture images of body tissue. OCT helps to provide detailed images of tissues that can be penetrated by light.
If there are suspicions of DME or severe diabetic retinopathy, a fluorescein angiogram may be done to ascertain the presence of damaged or leaky blood vessels.
How can people with diabetes protect their vision?
Prevention is always better than cure, especially when the damages are irreversible, as in the case of vision loss due to diabetic retinopathy. It is important to detect the disease early so as to treat it early, and because the early stages are so asymptomatic, everyone with diabetes should be screened or get a comprehensive dilated eye exam at least once yearly. Of course, people diagnosed with diabetic retinopathy will need eye exams more frequently.
Also, pregnant women with diabetes should have a comprehensive dilated eye exam as soon as possible.
How is DME treated?
DME can be treated using several different therapies. These could be used solely or in conjunction with each other.
• Anti-VEGF Injection Therapy – These Anti-VEGF drugs are injected into the vitreous gel to block a protein called vascular endothelial growth factor (VEGF), which can stimulate abnormal blood vessels to grow and leak fluid. Thus, by blocking VEGF, the growth of abnormal vessels could be reversed. Some of these include Avastin, Lucentis, and Eylea.
• Focal/Grid Macular Laser Surgery- In this form of surgery, just a few to hundreds of small laser burns are made to leaking blood vessels in areas where there is edema near the center of the macula. These laser burns for DME help to slow the leakage of fluid, reducing swelling in the retina. It is a one-session procedure but some persons may need more than one.
• Corticosteroids – These common drugs can either be injected or implanted into the eye and may be used in solitude or in conjunction with other drugs or laser surgery. The Ozurdex (dexamethasone) implant is done for short-term use, while the Iluvien (fluocinoloneacetonide) implant is longer lasting.
How is proliferative diabetic retinopathy (PDR) treated?
Laser surgery is the mainstay of treatment and it has been very successful given the fact that it has vastly remained unchanged for many decades. The treatment involves making about 1,000 to 2,000 tiny laser burns in areas of the retina away from the macula. These are done in an attempt to cause abnormal blood vessels to shrink.