Diabetic Retinopathy

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Diabetic Retinopathy

Diabetes is a chronic health condition that impacts how the body processes glucose (sugar) in the bloodstream, leading to elevated levels of blood sugar. The disease can increase the risk of developing a myriad of health issues, including high blood pressure, kidney damage, heart disease, and vision problems. One of the most common eye diseases associated with diabetes is diabetic retinopathy, a potentially blinding condition. It is one of the leading causes of permanent vision loss in adults in the US.

Diabetes and General Health

When we eat, most of the food we consume breaks down into sugars that are used to power our cells. This process is regulated by a peptide hormone known as insulin, which is produced by the pancreas and facilitates the cell’s ability to use glucose as fuel or store it for later. In diabetes, the pancreas either doesn’t produce enough insulin to properly process blood sugar or the cells stop responding to the insulin. Because the glucose isn’t being properly metabolized, it remains in the bloodstream for an excessive amount of time.

There are two types of diabetes: type 1 and type 2. Both types can have a significant impact on health, but the primary difference between them is that type 1 diabetes is considered to be a genetic autoimmune disease, while type 2 diabetes is typically caused by lifestyle factors. According to the Centers for Disease Control and Prevention, type 2 diabetes accounts for 90 to 95% of all diabetes cases.

Diabetes and Retina Health

One of the effects of having excessive glucose levels in the bloodstream is that it reduces the elasticity of blood vessels throughout the body. This can cause the blood vessels to tighten up, thus restricting blood flow and ultimately limiting how much blood and oxygen is supplied to various bodily systems.

Although the retina is very small and thin, it’s exceedingly complex and constantly at work whenever our eyes are open. To make our vision possible, the retina relies on a specialized vascular system to cycle a near-constant supply of fresh oxygenated blood. When excessive blood sugar damages the retinal blood vessels, it causes diabetic retinopathy.
Diabetic retinopathy is a progressive condition in which damaged blood vessels leak and bleed into the retina, causing a wide range of vision problems. If detected early on, patients are often able to maintain their vision. However, if the disease progresses unchecked, it can lead to permanent loss of vision.

Types of Diabetic Retinopathy

There are two types of diabetic retinopathy: background, or nonproliferative, diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR).

Background or Nonproliferative Diabetic Retinopathy (NPDR)

Diabetic retinopathy begins as NPDR. During the earliest phases, blood vessel damage is relatively minimal. At this point, only small amounts of fluid and blood have started to seep into the retina. NPDR can cause a wide range of changes to the eye, including:

• Microaneurysms: small lumps in the retinal blood vessels that leak fluid and cause swelling in the retina
• Retinal hemorrhages: abnormal bleeding in the retinal blood vessels
• Hard exudates: accumulations of cholesterol and other fatty debris from blood leaking into the retina
• Macular edema: swelling of the macula caused by excessive fluid and leakage in the retinal vascular system
• Macular ischemia: a process in which capillaries within the retinal vascular system atrophy, become obstructed, or constrict

Many patients with diabetes have only a mild case of NPDR, which typically doesn’t have any noticeable symptoms. Many changes to the eye during this stage are only observable during a comprehensive eye exam. When NPDR does impact vision, it is usually due to the presence of macular edema and/or macular ischemia.

Proliferative diabetic retinopathy (PDR)

The more advanced stage of diabetic retinopathy is known as proliferative diabetic retinopathy (PDR). PDR is characterized by a process known as neovascularization, which is when the retina tries to grow new blood vessels. This occurs because blood flow to the retina has been obstructed by the presence of numerous ischemic blood vessels. In an attempt to correct the issue, the retina grows new blood vessels. However, the new blood vessels are irregular and extremely fragile.

Instead of delivering blood, these abnormal blood vessels leak and bleed into the retina and vitreous, also known as vitreous hemorrhage. As the blood accumulates, it prevents light from passing through the eye and reaching the retina. If the hemorrhage is small, patients may see a few dark floaters in their field of vision. Floaters are small specks or squiggly lines scattered across your vision. If the hemorrhage is large, it can block out vision entirely. Although this can be a very alarming experience, vitreous hemorrhage does not cause permanent vision loss on its own. Unless the macula has been significantly damaged, vision can often return to normal once the blood clears away.

Neovascularization in the retina is also typically accompanied by the formation of scar tissue, which can cause puckering of the retinal tissue. Known as a macular pucker or epiretinal membrane, the wrinkling of the retina typically causes visual distortions. In some cases, the malformation of the retinal tissue can cause what is known as a traction retinal detachment. This type of retinal detachment occurs when scar tissue adheres to the retina and then shrinks away, pulling the retina out of its normal position. If large portions of the retina or the central macular become detached, it can cause significant and permanent vision loss. Retinal detachments are considered to be medical emergencies and must be addressed and treated as quickly as possible.

PDR can also lead to neovascular glaucoma (NVG), which occurs when several retinal blood vessels become ischemic. NVG is characterized by neovascularization in the iris, which is the pigmented tissue that surrounds the pupil at the front of the eye. In NVG, new abnormal blood vessels prevent fluid from coming out of the eye, which leads to elevated pressure inside the eye. In more severe cases of NVG, this can lead to damage to the optic nerve.

Diabetic Retinopathy Diagnosis & Treatment

Diabetic retinopathy is much easier to manage and treat when caught during the earlier stages of the disease. It’s recommended that patients with type 1 diabetes undergo a dilated eye exam and comprehensive retinal evaluation within the first five years of their diagnosis, while patients with type 2 diabetes should schedule a diabetic eye exam at the time of diagnosis. After their first initial exam, all patients with diabetes should plan on having an eye exam at least once a year. Patients who are diagnosed with diabetic retinopathy may need to see a retina specialist more frequently or need proactive retinal treatment, depending on how far the condition has progressed.

Treatment options for diabetic retinopathy can include:

• Laser therapy: also known as photocoagulation, laser therapy is sometimes used to weld-seal leaking blood vessels
• Anti-vascular endothelial growth factor (anti-VEGF) injections: Anti-VEGFs medications are injected directly into the eye to hinder the development of abnormal blood vessels
• Vitrectomy: a surgical procedure that involves removing vitreous fluid from inside the eye