Retinopathy is asymptomatic outside of vision change. No pain is associated with the condition, and people who develop the condition don’t feel pressure or leakage increasing because it happens so gradually. That is why physicians recommend diabetics to have regular, frequent eye exams even when no vision change is detected.
When leakage swells the retina, the most common symptom is decreased visual acuity, in which a person has trouble reading and driving and less ability to see fine details in facial features. The retina's rods and cones are able to receive light but cannot function well because of the fluid collecting around them. Approximately 20 percent patients with diabetic retinopathy have the leakage resulting in the retinal swelling called macular edema.
With proliferative diabetic retinopathy, blood leakage can occur into the large space inside the eye known as the vitreous cavity, and vision can decrease to a far worse degree. Patients notice the blood as dark spots, strands, and clouds floating in their vision. Nothing is visible on the eye’s surface when blood leaks into the vitreous cavity; the normally white sclera shows no sign of the blood inside the eye.
Diabetic retinopathy, a condition of diabetes mellitus, is incurable. Physicians do not know how to prevent capillary closure (see following paragraph) that stems from diabetes and can cause retinopathy. However, physicians can counsel diabetic patients about ways to decrease the likelihood of retinopathy’s emergence.
The eye has two blood supplies, each of which is integral to vision function. One supply travels through the choroid, under the retina, and the other travels through the retinal artery to supply the inner retina. Diabetes does not affect the choroid, but can severely diminish the amount of blood reaching the inner retina via the retinal artery. The specific cause is capillary closure – the tiny cells that line the inside of the capillaries stop functioning properly because of diabetes. Ischemia (insufficient blood supply) to the retina creates a reaction in which new blood vessels are made to assist; however, these fragile vessels break inside the eye, slowly leaking blood and other fluids, and creating a swollen, abnormal retina and bleeding inside the eye.
Diabetic retinopathy is limited to people who have the systemic disease diabetes mellitus (diabetes). Within the diabetes community, these additional risk factors are associated with retinopathy:
- High blood sugars – The higher your blood sugar level, the higher the risk.
- Blood pressure – The higher your blood pressure, the higher the risk.
Most cases of retinopathy are discovered during annual or regular exams associated with diabetes. Physicians recommend that people with type 1 (juvenile onset) diabetes should have a dilated eye exam every year beginning five years after initial diagnosis. People with type 2 (adult onset) diabetes should have a dilated eye exam every year, starting immediately at diagnosis.
Cases of diabetic retinopathy roughly approximate the populations of people who develop diabetes (more have type 2). However a 23-year-old who has had diabetes for 10 years would have about the same risk of developing retinopathy as someone who is 54 and has had diabetes 10 years.
Using a direct ophthalmoscope (an instrument with a light and multiple lenses), ophthalmologists examine patients’ eyes and can detect micro-aneurysms or balloon-shaped abnormal capillaries in the retina, which are the earliest sign of diabetic retinopathy. Ophthalmologists also can inject fluorescein dye into the patient and, using a blue light, photograph the retina's circulation. These pictures enable an ophthalmologist to document the aneurysms and leakage, and monitor changes in the patient's condition. Optical coherence tomography is another diagnostic tool, which allows ophthalmologists to measure how swollen the retina has become.
Onset of proliferative diabetic retinopathy is highly variable but tends to occur 10-12 years or longer after diabetes is diagnosed. This stage of retinopathy is characterized by growth of abnormal blood vessels on the surface of the optic nerve and retina. These vessels can cause extensive bleeding inside the eye, which can prevent light from reaching the retina. This condition can cause blindness and loss of all vision in some patients.
Most important are regular eye screenings by ophthalmologists, particularly for people with higher risk factors. Keeping blood-sugar and blood-pressure levels as low as possible also helps patients to avoid diabetic retinopathy or, if it has developed, to slow its progression.