Diabetes is a condition that causes hyperglycemia (high blood sugar). Over time, this can cause blood vessels to narrow, starving tissues of the oxygen and nutrients needed to function normally. When the eyes are involved, blurring can occur and may even progress to permanent vision loss.
This article looks at the symptoms and causes of blurred vision in people with diabetes. It also explains how diabetic eye diseases are diagnosed, treated, and prevented.
Symptoms
Diabetic eye diseases are a group of eye problems that tend to affect people with long-term diabetes. Blurred vision is a common feature, but other symptoms may accompany depending on which part of the eye is affected.
These conditions include diabetic retinopathy, diabetic macular edema, glaucoma, and cataracts. The problem may be bilateral (affecting both eyes) or unilateral (affecting only one eye).
Diabetic Retinopathy
Diabetic retinopathy affects the inner lining at the back of each eye, called the retina. This is the part of the eye that senses light and turns it into signals that the brain interprets as vision.
Symptoms of diabetic retinopathy include:
Blurred vision Floaters (spots or strings floating in your vision) Fluctuating vision Dark or empty spaces in your vision Vision loss
Diabetic Macular Edema
Diabetic macular edema causes swelling in the central part of the retina, called the macula, used for reading, driving, and recognizing faces. It occurs as an extension of diabetic retinopathy rather than on its own.
Symptoms of diabetic macular degeneration include:
Blurred vision at the center of the field visionWavy lines at the center of the field of visionWashed out or faded colorsCentral vision loss
Glaucoma
Glaucoma is a group of eye diseases that can damage the optic nerve that connects the eye to the brain. Uncontrolled diabetes is one such condition that can cause and/or accelerate glaucoma.
Symptoms of glaucoma include:
Blurred vision Eye pain or pressure Red eyes Headaches Seeing rainbow-colored halos around lights Tunnel vision Blind spots Nausea or vomiting Vision loss
Cataracts
Cataracts are the clouding of the lens of the eyes that often occurs with age. In people with uncontrolled diabetes, they tend to occur at an earlier age and ofter more severely.
Symptoms of cataracts include:
Blurred visionInability to see in dim lightSeeing halos around lightsVision loss
Causes of Diabetic Eye Diseases
At the heart of all diabetic eye diseases are persistently high blood glucose (sugar) levels. This can directly or indirectly cause damage to the structures of the eyes.
The damage caused to one part of the eye can have a knock-on effect, leading to additional eye complications and/or accelerating the progression of pre-existing eye diseases.
How Diabetic Retinopathy Occurs
High blood sugar can cause damage to very small blood vessels called capillaries. Over time, the build-up of sugar within capillaries can cause the walls to stick together and restrict the flow of blood to different organs of the body.
The restriction of blood flow to the back of the eyes can cause retinal scarring and symptoms of diabetic retinopathy.
How Diabetic Macular Edema Occurs
The blockage of blood vessels in the retina can cause them to swell, leading to the formation of tiny bulges known as microaneurysms.
As the walls of these vessels continue to thin, they can start to leak fluids into surrounding tissues, leading to the development of diabetic macular edema.
How Glaucoma and Cataract Occurs
To compensate for the loss of blood flow to the retina, new blood vessels may start to grow. These weaker vessels can easily rupture and bleed into the middle part of the eye. This not only causes scarring but increases the pressure within the eye to dangerously high levels.
High intraocular eye pressure is one of the key contributing factors to the development of glaucoma.
High blood sugar can also cause structural changes to the lens of the eye as deposits start to accumulate. This can accelerate the progression of cataracts in people with diabetes.
Can Diabetes Medications Cause Blurry Vision?
Blurred vision can also be the result of diabetes treatment itself.
People will often experience blurred vision a few days or weeks after changing their diabetes medications or treatment plan. These changes can cause short-term spikes in blood sugar and, in turn, increased intraocular pressure. The changes in pressure can cause blurring by increasing the distance between the retina and the lens.
Once blood glucose levels are normalized, the intraocular pressure will decrease and return your vision back to normal.
How to Treat Diabetic Eye Diseases
The main treatment for diabetic eye diseases is the tight control of your blood sugar levels. Early on, all that may be needed are frequent eye exams to check the status of your vision. Efforts would also be made to manage your diabetes with medications, diet, and exercise.
You would also need to control your blood pressure and cholesterol, both of which contribute to diabetic eye diseases. Cigarettes should be stopped as tobacco smoke causes blood vessels to further narrow, increasing the risk of diabetic retinopathy and diabetic macular edema.
Additional treatments may be prescribed if you sustain vision loss or are at risk of disease progression. These may involve:
Of the 285 million people living with diabetes around the world today, around one-third have signs of diabetic retinopathy. Of these, a further one-third have vision-threatening eye complications.
Another possible complication of diabetic retinopathy is a detached retina. This can occur spontaneously as scarring or new blood vessel growth displaces the retina from underlying tissues. A detached retina requires immediate medical care to avoid severe vision loss or blindness.
Risk factors for diabetic retinopathy and other diabetic eye diseases include:
Having diabetes for a long timePoor blood sugar controlHigh blood pressureHigh cholesterolSmoking cigarettesBeing Black, Latinx, or Native AmericanPregnancy
Are There Tests to Diagnose Diabetic Eye Disease?
If you have diabetes, your healthcare provider will want to regularly check your eyes for any abnormal changes whether you have symptoms or not.
If there are signs of diabetic retinopathy, you will be advised to undergo certain tests and procedures. This may involve a specialist known as an ophthalmologist who specializes in diseases of the eye.
A comprehensive eye exam may involve some or all of the following:
Visual acuity test (using an eye chart) Tonometry (used to measure intraocular pressure) Retinal exam (used to examine the retina by first dilating the pupils) Optimal coherence tomography (an imaging test used to generate a picture of your retina) Fluorescein angiogram (used to image the retina using an injectable contrast eye)
When to See a Healthcare Provider
Any changes to your vision warrant a visit to your healthcare provider if you have diabetes. With that said, you should seek immediate medical attention if you experience any of the signs and symptoms of a detached retina, including:
Sudden, severe changes in vision A sudden increase in floaters Sudden flashes of light Sudden darkening as if a curtain has been pulled over your eyes Seeing a persistent shadow at the side of your vision
Summary
Blurred vision is a common symptom in people with diabetes, particularly those with poorly controlled blood sugar. Persistently high blood glucose can cause progressive damage to structures of the eyes, leading to diabetic retinopathy, diabetic macular edema, glaucoma, or cataracts.
The primary treatment of diabetic eye disease is improved blood sugar control with medications and changes in lifestyle. Additional treatment may be needed to repair damage or prevent further injury to the retina, macula, optic nerve, or lens of the eye.
A Word From Verywell
If you are being treated for diabetes, it is in your best interest to have regular eye exams to check for any changes in the structure or function of your eyes.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) recommends a yearly eye exam for people with type 1 diabetes starting within five years of their diagnosis. People with type 2 diabetes should get a yearly eye exam as soon as they are diagnosed.
By spotting a problem early, your healthcare provider can prescribe treatments that may help preserve your long-term vision.
A1c test: Keeping your A1c goal below 7%Blood pressure: Keeping your blood pressure below 140/90 mm HgCholesterol: Keeping your “good” HDL cholesterol and “bad” LDL cholesterol within the optimal rangeSmoking cessation: To prevent further narrowing of blood vessels
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