Merck Manual

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Some Causes and Features of Blurred Vision

Some Causes and Features of Blurred Vision

Cause

Common Features*

Diagnosis†

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

Corneal scarring after an injury or an infection

Usually in people with a previous injury or infection

A doctor's examination

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)

Sometimes an eye imaging test

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

Retinitis pigmentosa (progressive deterioration of the retina)

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 (see hypertensive retinopathy), systemic lupus erythematosus (lupus), diabetes (see diabetic retinopathy), Waldenström macroglobulinemia, and multiple myeloma 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

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)

Ophthalmoscopy (using an instrument to painlessly look inside the eye)

Macular hole

Blurry vision initially in straight vision

Ophthalmoscopy (using an instrument to painlessly look inside the eye)

Optical coherence tomography (specialized imaging of the back of the eye)

Risk factors (for example, hypertension, age, glaucoma) Painless vision loss (usually sudden) Sometimes, blurry vision

Ophthalmoscopy (using an instrument to painlessly look inside the eye)

Sometimes, fluorescein angiography (using a fluorescent dye to take images of the back of the eye)

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

Optic neuritis (inflammation of the optic nerve), which can be related to multiple sclerosis

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

Disorders that affect focus

Refractive errors (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 only mentioned in this column if the diagnosis can be made only by the doctor's examination, without any testing.

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