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    Acute-Onset Flashes and Floaters

    Environmental Injuries / Exposures

    Last Updated Feb 08, 2023
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    By James Reid, Andrew Au


    • Floaters refer to the sensation of dark spots that are caused either by opacities in the vitreous which cast shadows.
    • Flashes are a visual phenomena known as photopsias and refer to perception of light in the absence of external stimuli.
    • Flashes and floaters are most often a result of benign age-related conditions, however a small percentage of patients have sight-threatening disease, thus early recognition and referral is prudent.
    • The most common cause of acute-onset flashes and floaters is posterior vitreous detachment (PVD) which involves separation of the posterior vitreous from the retina. If left untreated, this may progress to retinal detachment and blindness.

    Differential Diagnosis

    Diagnostic Process


    • Characteristics
      • Onset and duration of symptoms
      • Shape and volume of floaters
      • Unilateral or bilateral symptoms
      • Loss of vision
      • Presence of photopsias
      • Presence of scintillating scotomas
      • Presence of headaches
      • Presence of eye pain
      • Systemic signs or symptoms or focal neurological deficits
      • History of trauma
    • Classic migraine: amorphous pattern of lights or jagged lines and colours “marching” through the binocular visual field.
    • Past medical history: diabetes, migraine headaches, eye surgery, myopia, cataracts.

    Eye Examination

    • Visual acuity of each eye separately and with glasses or pinhole.
    • Visual fields to confrontation.
    • Relative afferent pupillary defect (RAPD).
    • Direct ophthalmoscopy is often insufficient as most retinal tears or detachments occur in the periphery.
    • Pupil dilation only if angles are open.
    • Ocular ultrasonography

    Referral Guidelines

    • Patients with symptoms of acute onset flashes or floaters and visual field loss need same day referral to ophthalmologist for dilated fundus exam.
    • Longstanding flashes and floaters require non-urgent referral.

    Patients at increased risk

    • Presence of subjective visual reduction (LR 5.0, 95% CI 3.1-8.1), vitreous hemorrhage (LR 10, 95% CI 5.1-20) or pigment (LR 44, 95% CI 2.3-852) – increased risk of retinal tear.
    • These patients require referral within 24 hours.
    • Slit lamp focused on anterior vitreous: look for vitreous hemorrhage or pigment.
    • Patients with acute onset floaters or flashes but no visual field defects should be seen within one week.

    Red flags

    • 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.

    Related Information

    Reference List

    1. Hollands, H., Johnson, D., Brox, A. C., Almeida, D., Simel, D. L., & Sharma, S. (2009). Acute-onset floaters and flashes: is this patient at risk for retinal detachment?. Journal of the American medical association, 302(20), 2243-2249.

    2. Johnson, D., & Hollands, H. (2012). Acute-onset floaters and flashes. Canadian medical association journal, 184(4), 431-431.

    3. Kahawita, S., Simon, S., & Gilhotra, J. (2014). Flashes and floaters: A practical approach to assessment and management. Australian Family Physician, 43(4), 201-203.

    4. Lumi, X., Hawlina, M., Glavač, D., Facskó, A., Moe, M. C., Kaarniranta, K., & Petrovski, G. (2015). Ageing of the vitreous: from acute onset floaters and flashes to retinal detachment. Ageing research reviews, 21, 71-77.


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