Flashes and Flickers

  • Flashes are bright sparks or streaks of light that appear suddenly and briefly in vision
  • Flashes usually come from tugging on retinal photoreceptors, which may signal impending or actual vitreous detachment, retinal hole, or retinal detachment
  • Flickers are sparkles that shimmer in vision ("scintillations")
  • Flickers usually come from activated visual cortex in migraine, but importantly also in transient ischemic attack, seizure, damaged retina, and damaged optic nerve
  • Flashes appear abruptly like lightning bolts in outer edge of visual field
  • Flashes may be provoked by eye movement
  • Flickers may be transient or persistent
  • Flickers that are part of visual aura of migraine often expand across hemifield in 20-30 minutes and disappear
  • Flickers of migraine usually precede headache and other manifestations
  • Flickers of damaged retina or optic nerve are often persistent
  • Halos around viewed objects (corneal disorders, acute angle-closure glaucoma)
  • Yellow-tinged borders ("xanthopsia") around viewed objects (digitalis excess, other medications)
  • Strobe-like hallucinations (anxiety)
  • Refer patient with flashes urgently to ophthalmologist because they suggest intraocular disorder (vitreous, retina, optic nerve)
  • Refer patient with flickers urgently to ophthalmologist, neuro-ophthalmologist or neurologist unless diagnosis of migraine is obvious because they could also suggest transient ischemic attack or seizure
  • Vitreous detachment may rarely cause retinal tear and detachment which must be repaired promptly to protect vision
  • Visual aura of migraine is usually harmless, but transient ischemic attack and seizure have health consequences