According to the National Eye Institute, changes in the eyes caused by diabetes—characterized by elevated blood sugar levels—are the leading cause of blindness in adults aged 25 to 64 in the United States.
Diabetes causes leakage by weakening the structure of small blood vessels throughout the body. The blood vessels in the eye are tiny and easily damaged by prolonged high blood sugar levels. If these blood vessels corrode, they have the potential to leak into the vitreous and retina. The vitreous is the gel-like substance found behind the lens. The retina is a layer of light-sensitive tissue at the back of your eyeball that converts images into electric signals that are transmitted to your brain via the optic nerve.
Tests are never fun, but in order to diagnose DME, your doctor will need to perform a battery of them in order to assess the state of your macula and determine the best course of treatment. The main function of the macula is to process information in our central vision. When it is impaired, such as with DME, our central vision begins to deteriorate while our peripheral vision remains unaffected. What to expect from each DME eye test is as follows:
You've probably taken a visual-acuity test if you've ever been to the eye center. It is the exam that employs a standardized chart of varying letter sizes (called a Snellen chart). Your doctor will ask you to sit or stand 20 feet (or 6 meters) away from the chart and cover one eye while reading certain lines of letters aloud. This test assists your doctor in determining how well you can see through your central vision and whether your vision is deteriorating.
The Amsler grid and visual acuity are subjective visual tests used to determine the extent of vision damage in a patient. The Amsler grid is a grid with many identical squares, white lines, and a black background. This test is used to determine whether the patient's vision is distorted and which areas of their visual field are affected. If the white lines in the grid appear curved or wavy, this could be due to fluid within the macula.
This non-invasive test involves putting special drops in your eyes that affect the muscles of your iris, causing your pupils to dilate. The dilated-eye exam is the only way for your eye doctor to see the peripheral part of your retina and determine if there are any other issues affecting it.
During the examination, your doctor will use an "indirect ophthalmoscope," which is a fancy way of saying they will shine a bright light into your eye to examine the retina. This shouldn't be too painful, but you should brace yourself for an intense light show.
A variety of imaging studies, such as this one, are also used to diagnose diabetic macular edema. Ocular coherence tomography (OCT) measures retinal thickness to determine the amount of fluid or swelling in the macula. The test employs a specialized light and a camera to provide detailed images of the retina's cell layers. Your doctor can use these tools to determine the thickness of your retina, which can aid in determining whether the macula is swollen.
If your doctor suspects DME based on your eye exam and OTC results, you may need to have a fluorescein angiogram. This one isn't too bad either but be warned: getting a shot is involved. Your doctor will use a needle to inject you with a small amount of fluorescein, a yellow dye that reaches the blood vessels in the eye about 10-15 seconds after being injected into the arm. When it reaches the eyes, it causes them to fluoresce, or shine brightly.
Fluorescein angiography is used to examine the health of the blood vessels in the eye. The dye injected into the eye illuminates the blood vessels and can reveal whether any of the blood vessels are actively leaking within the macula.