Diabetic retinopathy is a complication of diabetes that affects the retina, the light-sensitive tissue at the back of the eye. It develops when high blood sugar damages the small blood vessels in this tissue. The first detectable sign of this damage is often the appearance of tiny bulges in the vessel walls, known as microaneurysms. These abnormalities are an early warning sign that vision may eventually be impacted, making them a focus in managing diabetic eye disease.
The Formation of Microaneurysms
Sustained high blood glucose is toxic to the retina’s blood vessels, particularly the capillaries. These small vessels are supported by cells called pericytes, which also help regulate blood flow. High blood sugar leads to the loss of these pericytes, leaving the capillary walls weak and unstable.
Without the support from pericytes, the vessel walls stretch and balloon outward under blood flow pressure, creating a microaneurysm. This formation is like a weak spot bulging on a garden hose wall. These fragile bulges can become leaky over time.
Microaneurysms can leak blood, plasma, and lipids into the surrounding retinal tissue. During an eye exam, they appear as small red dots, sometimes with surrounding yellowish rings of lipid deposits. This leakage occurs because the damage from high glucose compromises the blood-retina barrier, a specialized lining within the vessels.
Detection and Clinical Signs
Early-stage diabetic retinopathy is asymptomatic. A person will not feel microaneurysms forming, and they do not cause vision changes at this point. For this reason, routine and comprehensive eye screenings are an important part of care for individuals with diabetes, allowing for early detection.
An ophthalmologist can observe the retina during a dilated eye exam. Microaneurysms appear as tiny red dots and are the earliest clinical sign of the disease. Fundus photography provides a high-resolution picture of the retina, which documents the number and location of these spots for future comparison.
Other technologies can assess the impact of these leaky vessels. Optical Coherence Tomography (OCT) is a non-invasive scan that uses light waves to create a cross-sectional map of the retina. This allows doctors to measure retinal thickness and detect any swelling caused by fluid leakage. A fluorescein angiogram may be performed for a more detailed assessment, which involves injecting a special dye into the bloodstream and taking rapid photographs of the retina to highlight any points of leakage.
Progression to Advanced Retinopathy
The presence of microaneurysms marks the first stage of the disease, Non-Proliferative Diabetic Retinopathy (NPDR). This stage is defined by changes within existing retinal blood vessels, not the growth of new ones. The number and severity of microaneurysms help an ophthalmologist gauge the risk of the disease advancing to more vision-threatening stages.
Leaky microaneurysms can lead to diabetic macular edema (DME). This occurs when fluid leaks into the macula—the central part of the retina responsible for sharp vision—causing it to swell. This swelling can result in blurred or distorted vision and is a common cause of vision loss from diabetic retinopathy.
If retinal damage continues, it can lead to poor circulation in the retina. This triggers the eye to grow new blood vessels, a phase known as Proliferative Diabetic Retinopathy (PDR), which is a more advanced form of the disease. These new vessels are abnormal and fragile. They can bleed into the vitreous gel that fills the eye, causing significant vision loss.
Managing Microaneurysms and Preventing Vision Loss
Managing diabetic retinopathy starts with controlling the systemic disease. The primary approach is managing blood glucose levels, measured by the HbA1c test. Maintaining stable blood sugar can significantly slow the onset and progression of retinopathy by preventing the initial damage to retinal capillaries.
Controlling blood pressure and cholesterol levels is also part of the systemic approach. Hypertension increases stress on weakened blood vessels, raising the likelihood of leakage. High lipid levels can contribute to the hard exudates, or deposits, seen in the retina with microaneurysms.
When microaneurysms are present but not causing macular edema, they are monitored with regular eye exams. Ocular treatment is initiated only when complications that threaten vision arise, such as DME. Treatments are directed at stopping the leakage. Anti-VEGF injections involve administering medication into the eye that targets a protein responsible for abnormal vessel growth and leakage, while focal laser therapy uses a laser to seal specific leaking microaneurysms. These interventions treat the consequences of microaneurysms rather than the bulges themselves.