Merck Manual

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Some Causes and Features of Blurred Vision

Some Causes and Features of Blurred Vision


Common Features*

Diagnostic Approach†

Clouding of normally transparent eye structures

Symptoms that begin gradually

Loss of the ability to distinguish between light and dark (loss of contrast) and glare (seeing halos and star bursts around lights)

Often in people with risk factors (such as older age or use of corticosteroids)

A doctor's examination alone

Corneal scarring after an injury or an infection

Usually in people with a previous injury or infection

A doctor's examination alone

Disorders that affect the retina

Usually symptoms that begin gradually

Loss of central vision (what a person is looking at directly) much more than peripheral vision (what is seen out of the corner of the eye)

A doctor's examination

Sometimes, an eye imaging test, such as optical coherence tomography (specialized imaging of the back of the eye) or fluorescein angiography (using a fluorescent dye to take images of the back of the eye)

Infection of the retina (as may be caused by cytomegalovirus or Toxoplasma parasites)

Usually in people who have HIV infection or another disorder that weakens the immune system

Often eye redness or pain

Tests to check for organisms suspected to be causing the infection

Symptoms that begin gradually

Primarily night blindness

Specialized testing (such as measuring the retina's responses to light in various conditions), done by an ophthalmologist

Retinopathy (damage of the retina) associated with a bodywide disorder such as high blood pressure High Blood Pressure High blood pressure (hypertension) is persistently high pressure in the arteries. Often no cause for high blood pressure can be identified, but sometimes it occurs as a result of an underlying... read more High Blood Pressure (see hypertensive retinopathy Hypertensive Retinopathy Hypertensive retinopathy is damage to the retina (the transparent, light-sensitive structure at the back of the eye) caused by high blood pressure. When blood pressure is high (a condition called... read more ), systemic lupus erythematosus ( lupus Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic autoimmune inflammatory connective tissue disorder that can involve joints, kidneys, skin, mucous membranes, and blood vessel walls. Problems in the... read more Systemic Lupus Erythematosus (SLE) ), diabetes Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more (see diabetic retinopathy Diabetic Retinopathy Diabetic retinopathy is damage to the retina (the transparent, light-sensitive structure at the back of the eye) as a result of diabetes. Blood vessels in the retina can leak blood and fluid... read more Diabetic Retinopathy ), Waldenström macroglobulinemia Macroglobulinemia Macroglobulinemia is a plasma cell cancer in which a single clone of plasma cells produces excessive amounts of a certain type of large antibody (IgM) called macroglobulins. Although many people... read more , and multiple myeloma Multiple Myeloma Multiple myeloma is a cancer of plasma cells in which abnormal plasma cells multiply uncontrollably in the bone marrow and occasionally in other parts of the body. People often have bone pain... read more or other disorders that can cause thickening of the blood (hyperviscosity syndrome)

Often in people known to have such disorders

Usually other symptoms in addition to loss of vision

A doctor's examination

Tests to check for disorders suspected to be causing retinopathy

Risk factors (for example, diabetic retinopathy, uveitis, retinal detachment or ocular injury)

Blurry or distorted vision (eg, straight lines appear wavy)

A doctor's examination alone

Macular hole

Blurry vision initially in straight-ahead vision

Optical coherence tomography

Risk factors (for example, hypertension, age, glaucoma)

Painless vision loss (usually sudden)

Sometimes, blurry vision

A doctor's examination

Sometimes, fluorescein angiography

Sometimes, optical coherence tomography (specialized imaging of the back of the eye)

Disorders that affect the optic nerve or its connections in the brain

Missing stairs and not seeing parts of written or typed words

Measurement of pressure inside the eye (tonometry), examination of the angles between eye structures such as the cornea and iris (gonioscopy), and optic nerve testing, done by an ophthalmologist

Usually mild pain that may worsen when one eye (often) or both eyes are moved

Partial or complete loss of vision

Symptoms that can become severe in hours or days

No effect on the eyelids and cornea

Often, MRI with contrast of the brain and orbits

Disorders that affect focus

Refractive errors Refractive Disorders (such as nearsightedness, farsightedness, and astigmatism)

Sharpness of vision (visual acuity) that varies with distance from objects

Decreased acuity that can be corrected by using glasses or a pinhole device

Testing of refraction by an optometrist or ophthalmologist

* Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present.

† Although a doctor's examination is always done, it is mentioned in this column only if the diagnosis can be made only by the doctor's examination, without any testing.

HIV = human immunodeficiency virus; MRI = magnetic resonance imaging.