Blurred vision is the most common visual symptom. It usually refers to decreased visual clarity of gradual onset, and corresponds to decreased visual acuity. For sudden, complete loss of vision in one or both eyes (blindness). Patients with small visual field defects (eg, caused by a small retinal detachment) may describe their symptoms as blurring.
Etiology
The most common causes of blurred vision (see table Some Causes of Blurred Vision) include
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Refractive errors (the most common cause overall)
Blurred vision has 4 general mechanisms:
Some Causes of Blurred Vision
Cause |
Suggestive Findings |
Diagnostic Approach |
Opacification of eye structures |
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Gradual onset, often risk factors (eg, aging, corticosteroid use), loss of contrast, glare Lens opacification on ophthalmoscopy or slit-lamp examination |
Clinical evaluation |
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Corneal opacification (eg, posttraumatic or postinfectious scarring) |
Corneal abnormalities on slit-lamp examination |
Clinical evaluation |
Disorders affecting the retina |
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Gradual onset, central vision affected (central scotoma) without loss of peripheral vision, macular drusen or scarring, neovascular membrane |
Fundoscopy Fluorescein angiography or other retinal imaging as clinically indicated |
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Infectious retinitis (eg, cytomegalovirus, Toxoplasma) |
Usually HIV infection or other immunosuppressive disorder, often eye redness or pain, abnormal retinal findings |
Fundoscopy Studies as clinically indicated (eg, anti-Toxoplasma antibodies) |
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Primarily night blindness, gradual onset, pigmented retinal lesions |
Fundoscopy Specialized testing by ophthalmologist (eg, dark adaptation, electroretinography) |
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Retinopathy associated with systemic disorders (eg, hypertension, systemic lupus erythematosus, diabetes, Waldenström macroglobulinemia, multiple myeloma, or other disorders that could cause hyperviscosity syndrome) |
Risk factors, retinal abnormalities detected during ophthalmoscopy (see table Red Flag Findings) |
Testing as indicated for clinically suspected disorders |
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Risk factors (eg, diabetic retinopathy, uveitis, retinal detachment or ocular injury) Blurry or distorted vision (eg, straight lines appear wavy) |
Fundoscopy Optical coherence tomography |
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Macular hole |
Blurry vision, initially central |
Fundoscopy Optical coherence tomography |
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Risk factors (eg, hypertension, age, glaucoma) Painless vision loss (usually sudden) Sometimes, blurry vision |
Fundoscopy Sometimes, fluorescein angiography Sometimes, optical coherence tomography |
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Disorders affecting the optic nerve or neural pathways |
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Gradual onset unless due to multiple sclerosis (in which onset of optic neuritis is rapid) Often unilateral or asymmetric Pain with eye movement, direct pupillary light reflex decreased more than consensual (afferent pupillary defect), sometimes loss of optic disk margins and/or globe tenderness |
Often MRI to rule out multiple sclerosis |
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Disorders affecting focus |
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Visual acuity varying with distance from objects, acuity corrected with refraction |
Clinical refraction by an optometrist or ophthalmologist |
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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.
Patients with certain disorders that cause blurred vision (eg, acute corneal lesions [such as abrasions], ulcers, herpes simplex keratitis, herpes zoster ophthalmicus, acute angle-closure glaucoma) are more likely to present with other symptoms such as eye pain and red eye.
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
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, diabetes, HIV/AIDS, systemic lupus erythematosus, sickle cell anemia, disorders that could cause hyperviscosity syndrome such as multiple myeloma or Waldenström macroglobulinemia). Drug history should include questions about use of drugs that could affect vision (eg, corticosteroids) and treatments for disorders affecting vision (eg, 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, 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. 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
The following findings are of particular concern:
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Sudden change in vision
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Eye pain (with or without eye movement)
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Visual field defect (by history or examination)
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Visible abnormality of the retina or optic disk
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HIV/AIDS or other immunosuppressive disorder
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A systemic disorder that could cause retinopathy (eg, sickle cell anemia, possible hyperviscosity syndrome, diabetes, hypertension)
Interpretation of findings
Symptoms and signs help suggest a cause (see table Some Causes of Blurred Vision).
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) 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.
Specific retinal findings help suggest a cause (see table Interpretation of Retinal Findings).
Interpretation of Some Red Flag Findings
Findings |
Possible Cause |
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Findings suggesting a systemic disorder that could cause retinopathy (eg, sickle cell anemia, possible hyperviscosity syndrome, diabetes, hypertension) |
Retinopathy |
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Bilateral symmetric visual field defects |
Lesion affecting cortical visual pathways |
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Eye pain* |
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Findings suggesting HIV/AIDS or other immunosuppressive disorder* |
Infectious retinitis |
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Monocular visual field defect* |
Retinal detachment, other retinal abnormality, other optic neuropathy |
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Retinal or optic disk abnormality |
Infectious retinitis,* retinitis pigmentosa, worsening retinopathy* (see table Retinal Findings) |
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Sudden change in vision* |
Optic neuritis, sudden worsening of retinopathy, or other physical eye disorder (see Acute Vision Loss) |
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*Urgent or immediate ophthalmologic referral is usually indicated. |
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Interpretation of Retinal Findings
Findings |
Possible Cause |
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Arteriolar narrowing, copper wiring, flame hemorrhages, arteriovenous nicking |
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Dark-pigmented lesions in bone spicule formation in the midperipheral retina (rarely visible with direct ophthalmoscopy) |
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Diffuse hemorrhages, venous dilation |
Hyperviscosity syndrome |
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Indistinct optic disk margins, suggesting optic nerve swelling |
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Macular hyperpigmentation, loss of pigment in retinal epithelium, drusen, hemorrhage |
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Microaneurysms and neovascularization at posterior retina |
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White retinal infiltrates, sometimes loss of red reflex or visible vitreous inflammation |
Infectious retinitis Toxoplasmosis suggested by retinal infiltrate immediately adjacent to a scar |
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:
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Diabetes: Fingerstick or random glucose measurement
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Poorly controlled hypertension and acute hypertensive retinopathy (hemorrhages, exudates, or papilledema): Urinalysis, renal function testing, blood pressure monitoring, and electrocardiography (ECG)
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HIV/AIDS and retinal abnormalities: HIV serology and CD4+ count
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Systemic lupus erythematosus (SLE) and retinal abnormality: Antinuclear antibodies, erythrocyte sedimentation rate (ESR), and complete blood count (CBC)
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Waldenström macroglobulinemia, multiple myeloma, or sickle cell anemia: CBC with differential count and other testing (eg, serum protein electrophoresis) as clinically indicated
Treatment
Geriatrics Essentials
Key Points
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If visual acuity is corrected with pinhole refraction, refractive error is likely the problem.
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If pinhole refraction does not correct acuity and there is no obvious cataract or corneal abnormality, ophthalmoscopy should be done after pupillary dilation.
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Many abnormalities on ophthalmoscopy, particularly if symptoms are recently worsening, require urgent or immediate ophthalmologic referral.
