Blurry vision is the loss of sharpness of eyesight, making objects appear out of focus and hazy.
The primary causes of blurred vision are refractive errors nearsightedness, farsightedness and astigmatism or presbyopia. But blurry vision also can be a symptom of more serious problems, including a potentially sight-threatening eye disease or neurological disorder.
Blurred vision can affect both eyes, but some people experience blurry vision in one eye only.
Cloudy vision, where objects are obscured and appear “milky,” is often mistaken for blurry vision. Cloudy vision usually is a symptom of specific conditions such as cataracts, but blurry and cloudy vision can both be symptoms of a serious eye problem.
A qualified eye doctor can measure the extent of your blurred vision and determine the cause with a comprehensive eye exam, including spatial contrast sensitivity, slit-lamp and standard Snellen eye chart tests.
Sudden blurry vision that persists could be a sign of a serious health problem, and you should see a doctor immediately.
Blurred Vision Symptoms & Signs
Blurred vision refers to a lack of sharpness of vision resulting in the inability to see fine detail. Blurred vision may result from abnormalities present at birth such as nearsightedness or farsightedness that require corrective lenses (eyeglasses) or it may signal the presence of eye disease. Blurry vision may be experienced in one eye or in both eyes, depending upon the cause. Blurred vision can also be a symptom of numerous conditions that do not directly involve the eye, such as migraine or stroke. A number of medications may also lead to temporary blurring of vision as a side effect. Sometimes, blurred vision is associated with other symptoms, depending upon its cause, including headache, sensitivity to light, or redness and irritation of the eyes.
Causes of blurred vision
There are many different eye problems and conditions that can cause blurred vision. These include:
To understand how refractive errors cause blurred vision, it first helps to understand how the eye works.
Refractive errors that cause blurred vision include:
- Long sightedness: causes blurred vision when viewing objects close up, such as when reading a book or using a computer.
- Short sightedness: causes blurred vision when viewing objects at a distance, such as when watching television or driving.
- Astigmatism: causes blurred vision when viewing objects at any distance, from reading and computer use, to driving and watching television.
Cataracts are a clouding of the lens in your eye. At first, any blurred eyesight may be almost imperceptible. However, cataracts can eventually result in severe blurred vision that has a major impact on your independence.
If you have had a cataract removed and your blurry vision re-occurs, posterior capsule opacity also known as a ‘secondary cataract’ – may be the cause.
Diabetic retinopathy is a condition associated with diabetes. High blood sugar levels cause damage to the retina (the focusing surface at the back of the eye). The final stage of diabetic retinopathy, known as macular oedema, can cause blurred vision.
An epiretinal membrane is a thin, fibrous layer that forms over the retina (the focusing surface at the back of the eye). It acts like a film that partially blocks the light entering your eye, which results in blurred vision.
Keratoconus is an eye disease that results in a conically shaped cornea (the clear front ‘window’ of your eye). Because the cornea does much of the eye’s focusing, the irregular shape can cause blurred vision.
Macular degeneration and macular holes
The macula is the central part of the retina at the back of your eye. It allows you to see detail, colour, and things directly in front of you. Macular degeneration and macular holes damage the macula, causing central vision to become blurred.
A detached retina is a serious medical emergency that can cause sudden blurred vision. It may also cause a number of other symptoms, such as flashes and floaters, and sudden blindness.
Retinal vein occlusion
If the blood vessels that feed the retina (the focusing surface at the back of the eye) become blocked, it is known as a retinal vein occlusion. This can cause sudden blurred vision, and also sudden blindness.
A pterygium is a benign growth that occurs on the surface of the eye. Sometimes, a pterygium can grow onto the cornea. If this occurs, it can alter the shape of the cornea, causing blurred vision.
If blood leaks into the vitreous ‘gel’ that fills your eye, it can block the light that enters your eye, causing blurred vision. Vitreous haemorrhage can be caused by trauma or injury, or it may be a result of an eye condition, such as diabetic retinopathy.
Eye infection, inflammation or injury
Many people suffer blurry vision as a result of an eye infection or injury. Eyelid and eyelash problems can sometimes cause blurred vision, as can the common eye infection conjunctivitis.
Diabetes and Blurred Vision
Don’t run out and buy a new pair of glasses as soon as you notice you have blurred vision. It could just be a temporary problem that develops rapidly and is caused by high blood sugar levels.
High blood sugar causes the lens of the eye to swell, which changes your ability to see. To correct this kind of blurred vision, you need to get your blood sugar back into the target range. For many people this is from70 mg/dL to 130 mg/dL before meals and less than 180 mg/dL one to two hours after the start of a meal. Ask your doctor what your personal target range should be.
Blurred vision can also be a symptom of more serious eye problems. If your vision is blurred, contact your doctor.