Floaters: A Merck Manual of Patient Symptoms podcast

Floaters are opacities that move across the visual field and do not correspond to external visual objects.

Pathophysiology

With aging, the vitreous humor can contract and separate from the retina. The age at which this change occurs varies but most often is between 50 and 75 yr. During this separation, the vitreous can intermittently tug on the retina. The mechanical traction stimulates the retina, which sends a signal that is perceived by the brain and interpreted as light. Complete separation of the vitreous leads to an increase in floaters, which may last for years.

However, traction on the retina may create a hole (retinal tear), and if fluid leaks behind the tear, the retina may detach. Retinal detachment may also be caused by other factors (eg, trauma, primary retinal disorders). Lightning-like flashes, common in retinal detachment, are called photopsias. Photopsias can also occur when rubbing the eyes or when looking around after awakening.

Etiology

The most common cause of vitreous floaters is

• Idiopathic contraction of the vitreous humor

Less common causes are listed in Table 10: Symptoms of Ophthalmologic Disorders: Some Causes of Floaters.

Rare causes of floaters include intraocular tumors (eg, lymphoma) and vitritis (inflammation of the vitreous). Intraocular foreign bodies can cause floaters but usually manifest with other symptoms, such as loss of vision, eye pain, or redness.

Table 10
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Some Causes of Floaters Cause Suggestive Findings* Diagnostic Approach Benign disorders Idiopathic vitreous floaters Mild, stable floaters that come into the field of view intermittently and move as the eye moves Often shaped like cells or strands Translucent May be more noticeable under certain lighting conditions (eg, in bright sunlight) Normal vision May occur in both eyes, although not synchronously Normal eye examination Clinical evaluation Serious vitreous and retinal disorders Retinal detachment Sudden, spontaneous, continuous shower of lightning-like flashes (photopsias) Curtain of vision loss moving across the visual field, visual field defect (usually peripheral) Abnormal retinal examination (eg, detached retina appears as a pale billowing parachute) Possible risk factors (eg, recent trauma, eye surgery, severe myopia) Indirect ophthalmoscopy by an ophthalmologist after pupillary dilation Retinal tear Sudden, spontaneous photopsias May occur in the periphery of the retina and may be visible only by indirect ophthalmoscopy Indirect ophthalmoscopy by an ophthalmologist after pupillary dilation Vitreous detachment Increase in unilateral floaters over 1 wk–3 mo in patients with average age of 50–75 yr Floaters that are cobweb-like One large floater that moves in and out of central vision Spontaneous photopsias Indirect ophthalmoscopy by an ophthalmologist after pupillary dilation Vitreous hemorrhage History of proliferative diabetic retinopathy or trauma Loss of vision that may affect entire visual field Loss of red reflex Indirect ophthalmoscopy by an ophthalmologist after pupillary dilation Vitreous inflammation (eg, cytomegalovirus, Toxoplasma, or fungal chorioretinitis) Pain Loss of visual acuity Loss of vision affecting the entire visual field Retinal lesions (sometimes cotton-like) that do not conform to an arterial or a venous territory Risk factors (eg, AIDS) Decreased red reflex May be bilateral Evaluation and testing as directed by an ophthalmologist, based on suspected cause Nonocular disorders Ocular migraine Bilateral, synchronous, flashing lights often zigzagging on the peripheral field for 10–20 min Possible blurring of central vision Possible headache after visual symptoms Possible migraine history Clinical evaluation *Unilateral unless otherwise specified.

Evaluation

The most important goal is to identify serious vitreous and retinal disorders. If these disorders cannot be ruled out, patients should be examined by an ophthalmologist using an indirect ophthalmoscope after pupillary dilation. Recognizing ocular migraine is also helpful.

History: History of present illness should ascertain onset and duration of symptoms and the shape and volume of floaters, as well as whether they are unilateral or bilateral and whether they have been preceded by trauma. The patient should try to distinguish floaters from lightning-like flashes of light (as in photopsias) or jagged lines across the visual field (as in migraine). Important associated symptoms include loss of vision (and its distribution in the visual field) and eye pain.

Review of systems should seek symptoms of possible causes, such as headaches (ocular migraine) and eye redness (vitreous inflammation).

Past medical history should note diabetes (including diabetic retinopathy), migraine headaches, eye surgery, severe myopia, and any disorders that could affect the immune system (eg, AIDS).

Physical examination: Eye examination should be reasonably complete. Best corrected visual acuity is measured. The eyes are inspected for redness. Visual fields are assessed in all patients. However, recognition of visual field defects by bedside examination is very insensitive, so inability to show such a defect is not evidence that the patient has full visual fields. Extraocular movements and pupillary light responses are assessed. If patients have a red eye or eye pain, the corneas are examined under magnification after fluorescein staining, and slit-lamp examination is done if possible. Ocular pressure is measured (tonometry).

Ophthalmoscopy is the most important part of the examination; it is done after dilating the pupils. To dilate the pupils, the physician first makes sure to record pupillary size and light responses, then instills drops, usually 1 drop each of a short-acting α-adrenergic agonist (eg, 2.5% phenylephrineSome Trade Names
NEO-SYNEPHRINE
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) and a cycloplegic (eg, 1% tropicamideSome Trade Names
MYDRAL
MYDRIACYL
TROPICACYL
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or 1% cyclopentolateSome Trade Names
AK-PENTOLATE
CYCLOGYL
CYLATE
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). The pupils are fully dilated about 20 min after these drops are instilled. Ophthalmoscopy is done by a nonophthalmologist using a direct ophthalmoscope. An ophthalmologist does indirect ophthalmoscopy, which provides a more complete view of the retina, particularly the periphery.

Red flags: The following findings are of particular concern:

• Sudden increase in floaters
• Photopsias
• Loss of vision, diffuse or focal (visual field defect)
• Recent eye surgery or eye trauma
• Eye pain
• Loss of red reflex
• Abnormal retinal findings

Interpretation of findings: Retinal detachment is suggested by sudden increases in floaters, photopsias, or any of its other, more specific characteristics (eg, visual field defects, retinal abnormalities). Bilateral synchronous symptoms suggest ocular migraine, although patients often have difficulty deciphering the laterality of their symptoms (eg, they often interpret scintillating scotoma of the left field of both eyes as left-eyed). Loss of red reflex suggests opacification of the vitreous (eg, vitreous hemorrhage or inflammation), but it also can be caused by advanced cataracts. Loss of vision suggests a serious disorder causing dysfunction of the vitreous or retina.

Testing: Patients who require evaluation by an ophthalmologist may need testing. However, tests can be selected by or in conjunction with the ophthalmologist. For example, patients suspected of having chorioretinitis may require microbiologic testing.

Treatment

Idiopathic vitreous floaters require no treatment. Other disorders causing symptoms are treated.

Key Points

• Floaters by themselves rarely indicate a serious disorder.
• Patients with any abnormal findings on examination require ophthalmologic referral.
• If floaters are accompanied by any other symptoms (eg, persistent flashing lights, visual deficit, sensation of a moving curtain of vision loss), patients require ophthalmologic referral, regardless of examination findings.

Last full review/revision November 2012 by Kathryn Colby, MD, PhD

Content last modified December 2012