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Diabetes is a condition in which the pancreas does not produce enough, or any, insulin, resulting in an excess of sugar in the blood. There are different variations of this disease, but all can affect the eye. Diabetes can damage specific parts of the eye, including the retina, vitreous, lens, and optic nerve.
How does diabetes affect the eyes?
Diabetes can lead to permanent eye damage. Patients can develop diabetic eye diseases like diabetic retinopathy, and are also at higher risk for developing cataracts, glaucoma, eye muscle problems causing double vision, and retinal detachments.
There are two types of diabetic retinopathy: nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR). NPDR is the earliest stage of diabetic retinopathy, when damaged blood vessels in the retina begin to leak extra fluid and small amounts of blood into the retinal tissue. Cholesterol or other fats from the blood may also deposit into the retina.
The leaking fluid can also cause a swelling or thickening of the macula, called macular edema. This is the most common cause of vision loss related to diabetes. Macular ischemia is when small blood vessels close and don’t provide adequate oxygen to the macula, causing the patient’s vision to blur.
Nonproliferative diabetic retinopathy
Many people with diabetes have mild NPDR, which usually does not affect their vision. However, if their vision is affected, it is because of macular edema or macular ischemia.
Proliferative diabetic retinopathy
PDR mainly occurs when many blood vessels in the retina are damaged, preventing enough blood flow. The retina responds by growing new blood vessels in an attempt to supply blood to the area where the original blood vessels are damaged. However, the new vessels are fragile and can bleed and fill the back portion of the eye with blood. The new blood vessels are also often accompanied by scar tissue that may cause the retina to wrinkle or detach.
If the retina wrinkles it can distort vision, and more severe vision loss can occur if the macula or large areas of the retina are detached.
PDR may cause more severe vision loss than NPDR because it can affect both central and peripheral vision. With a vitreous hemorrhage, the fragile new blood vessels can bleed into the vitreous – the gel in the center of the eye – preventing light rays from reaching the retina. If it’s a small hemorrhage, the patient may only see a few new, dark floaters, but a large hemorrhage might limit the amount of light that enters the eye, allowing them to primarily see only light and dark. However, when the blood clears vision may return to its former level unless the macula has been damaged.
People with diabetic retinopathy often don’t notice vision changes in the disease’s early stages, but as it progresses it usually causes vision loss that in many cases can’t be reversed. The longer the duration of diabetes, and the more uncontrolled the blood sugar, the more likely patients will suffer long-term damage.
Diabetic eye treatment
Diabetic patients should get their eyes checked regularly. Once a patient is diagnosed with diabetes, their primary care physician will refer them to an eye doctor to have their eyes checked with a dilated eye exam once a year. Yearly exams are recommended initially, but if retinopathic changes are noticed, their eye doctor may ask patients to come in more frequently. If treatments are needed, they will likely be referred to a retina specialist for laser treatments, injections of medications into the eye, or surgery.
Diabetic eye disease problems are preventable, though. Patients can prevent retinopathy and other related visual loss through tight blood sugar, blood pressure, and cholesterol control. This can be done through a combination of a good diet, regular exercise, and taking medications as directed by their primary care physician.