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Blurred Vision

By

Christopher J. Brady

, MD, Wilmer Eye Institute, Retina Division, Johns Hopkins University School of Medicine

Last full review/revision May 2021| Content last modified May 2021
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Topic Resources

Blurred vision is the most common visual symptom. It usually refers to decreased visual clarity of gradual onset, and corresponds to decreased visual acuity. Patients with small visual field defects (eg, caused by a small retinal detachment Retinal Detachment Retinal detachment is separation of the neurosensory retina from the underlying retinal pigment epithelium. The most common cause is a retinal break (a tear or, less commonly, a hole) (rhegmatogenous... read more Retinal Detachment ) may describe their symptoms as blurring.

Etiology of Blurred Vision

Blurred vision has 4 general mechanisms:

  • Opacification of normally transparent ocular structures (cornea, lens, vitreous) through which light rays must pass to reach the retina

  • Disorders affecting the retina

  • Disorders affecting the optic nerve or its connections

  • Refractive errors

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Certain disorders can have more than one mechanism. For example, refraction can be impaired by early cataracts or the reversible lens swelling caused by poorly controlled diabetes Diabetes Mellitus (DM) Diabetes mellitus is impaired insulin secretion and variable degrees of peripheral insulin resistance leading to hyperglycemia. Early symptoms are related to hyperglycemia and include polydipsia... read more .

Rare disorders that can cause blurred vision include hereditary optic neuropathies (eg, dominant optic atrophy, Leber hereditary optic neuropathy) and corneal scarring due to vitamin A deficiency.

Evaluation of Blurred Vision

History

History of present illness should ascertain the onset, duration, and progression of symptoms, as well as whether they are bilateral or unilateral. The symptom should be defined as precisely as possible by asking an open-ended question or request (eg, “Please describe what you mean by blurred vision”). For example, loss of detail is not the same as loss of contrast. Also, visual field defects may not be recognized as such by patients, who may instead describe symptoms such as missing steps or the inability to see words when reading. Important associated symptoms include eye redness, photophobia, floaters, sensation of lightning-like flashes of light (photopsias), and pain at rest or with eye movement. The effects of darkness (night vision), bright lights (ie, causing blur, star bursts, halos, photophobia), distance from an object, and corrective lenses and whether central or peripheral vision seems to be more affected should be ascertained.

Review of systems includes questions about symptoms of possible causes, such as increased thirst and polyuria (diabetes).

Past medical history should note previous eye injury or other diagnosed eye disorders and ask about disorders known to be risk factors for eye disorders (eg, hypertension Hypertension Hypertension is sustained elevation of resting systolic blood pressure (≥ 130 mm Hg), diastolic blood pressure (≥ 80 mm Hg), or both. Hypertension with no known cause (primary; formerly, essential... read more Hypertension , diabetes Diabetes Mellitus (DM) Diabetes mellitus is impaired insulin secretion and variable degrees of peripheral insulin resistance leading to hyperglycemia. Early symptoms are related to hyperglycemia and include polydipsia... read more , HIV/AIDS Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection results from 1 of 2 similar retroviruses (HIV-1 and HIV-2) that destroy CD4+ lymphocytes and impair cell-mediated immunity, increasing risk of certain... read more Human Immunodeficiency Virus (HIV) Infection , systemic lupus erythematosus Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic, multisystem, inflammatory disorder of autoimmune etiology, occurring predominantly in young women. Common manifestations may include arthralgias and... read more Systemic Lupus Erythematosus (SLE) , sickle cell anemia Sickle Cell Disease Sickle cell disease (a hemoglobinopathy) causes a chronic hemolytic anemia occurring almost exclusively in blacks. It is caused by homozygous inheritance of genes for hemoglobin (Hb) S. Sickle-shaped... read more Sickle Cell Disease , disorders that could cause hyperviscosity syndrome such as multiple myeloma Multiple Myeloma Multiple myeloma is a cancer of plasma cells that produce monoclonal immunoglobulin and invade and destroy adjacent bone tissue. Common manifestations include lytic lesions in bones causing... read more Multiple Myeloma or Waldenström macroglobulinemia Macroglobulinemia Macroglobulinemia is a malignant plasma cell disorder in which B cells produce excessive amounts of IgM M-proteins. Manifestations may include hyperviscosity, bleeding, recurring infections... read more ). Drug history should include questions about use of drugs that could affect vision (eg, corticosteroids) and treatments for disorders affecting vision (eg, diabetic retinopathy Diabetic Retinopathy Manifestations of diabetic retinopathy include microaneurysms, intraretinal hemorrhage, exudates, macular edema, macular ischemia, neovascularization, vitreous hemorrhage, and traction retinal... read more Diabetic Retinopathy ).

Physical examination

Nonvisual symptoms are evaluated as needed; however, examination of the eyes may be all that is necessary.

Testing visual acuity is key. Many patients do not give a full effort. Providing adequate time and coaxing patients tend to yield more accurate results.

Acuity ideally is measured while the patient stands 6 m (about 20 ft) from a Snellen chart posted on a wall. If this test cannot be done, near acuity can be measured using a chart held about 36 cm (14 in) from the eye. Measurement of near vision should be done with reading correction in place for patients > 40 years. Each eye is measured separately while the other eye is covered with a solid object (not the patient’s fingers, which may separate during testing). If the patient cannot read the top line of the Snellen chart at 6 m, acuity is tested at 3 m (about 10 ft). If nothing can be read from a chart even at the closest distance, the examiner holds up different numbers of fingers to see whether the patient can accurately count them. If not, the examiner tests whether the patient can perceive hand motion. If not, a light is shined into the eye to see whether light is perceived.

Visual acuity is measured with and without the patients’ own glasses. If acuity is corrected with glasses, the problem is a refractive error. If patients do not have their glasses, a pinhole refractor is used. If a commercial pinhole refractor is unavailable, one can be made at the bedside by poking holes through a piece of cardboard using an 18-gauge needle and varying the diameter of each hole slightly. Patients choose the hole that corrects vision the most. If acuity corrects with pinhole refraction, the problem is a refractive error. Pinhole refraction is a rapid, efficient way to diagnose refractive errors, which are the most common cause of blurred vision. However, with pinhole refraction, best correction is usually to only about 20/30, not 20/20.

Eye examination is also important. Direct and consensual pupillary light responses are examined using the swinging flashlight test. Visual fields are checked using confrontation and an Amsler grid.

The cornea is examined for opacification, ideally using a slit lamp. The anterior chamber is examined for cells and flare using a slit lamp if possible, although results of this examination are unlikely to explain visual blurring in patients without eye pain or redness.

The lens is examined for opacities using an ophthalmoscope, slit lamp, or both.

Ophthalmoscopy is done using a direct ophthalmoscope. More detail is visible if the eyes are dilated for ophthalmoscopy with a drop of a sympathomimetic (eg, 2.5% phenylephrine), cycloplegic (eg, 1% tropicamide or 1% cyclopentolate), or both; dilation is nearly full after about 20 minutes. As much of the fundus as is visible, including the retina, macula, fovea, vessels, and optic disk and its margins, is examined. To see the entire fundus (ie, to see a peripheral retinal detachment), the examiner, usually an ophthalmologist, must use an indirect ophthalmoscope.

Intraocular pressure is measured.

Red flags

Interpretation of findings

If visual acuity is corrected with glasses or a pinhole refractor, simple refractive error is likely the cause of blurring. Loss of contrast or glare may still be caused by cataract, which should be considered.

However, red flag findings suggest a more serious ophthalmologic disorder (see table Interpretation of Some Red Flag Findings Interpretation of Some Red Flag Eye Findings Blurred vision is the most common visual symptom. It usually refers to decreased visual clarity of gradual onset, and corresponds to decreased visual acuity. Patients with small visual field... read more ) and need for a complete examination, including slit-lamp examination, tonometry, ophthalmoscopic examination with pupillary dilation, and, depending on findings, possibly immediate or urgent ophthalmologic referral.

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Testing

If acuity corrects appropriately with refraction, patients are referred to an optometrist or ophthalmologist for routine formal refraction. If visual acuity is not corrected with refraction but there are no red flag findings, patients are referred to an ophthalmologist for routine evaluation. With certain red flag findings, patients are referred for immediate or urgent ophthalmologic evaluation.

Patients with symptoms or signs of systemic disorders should have appropriate testing:

Treatment of Blurred Vision

Underlying disorders are treated. Corrective lenses may be used to improve visual acuity, even when the disorder causing blurring is not purely a refractive error (eg, early cataract).

Geriatrics Essentials

Although some decrease in visual acuity in low light or loss of contrast sensitivity can normally occur with aging, acuity normally is correctable to 20/20 with refraction, even in very elderly patients.

Key Points

  • If visual acuity is corrected with pinhole refraction, refractive error is likely the problem.

  • If pinhole refraction does not correct acuity and there is no obvious cataract or corneal abnormality, ophthalmoscopy should be done after pupillary dilation.

  • Many abnormalities on ophthalmoscopy, particularly if symptoms are recently worsening, require urgent or immediate ophthalmologic referral.

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