Evaluation of Common Visual Disturbances: Flashing Lights, Floaters, and Other Transient Phenomena

Claudia U. Richter

Flashes of light, floaters, specks, distortions, halos, and discolorations are among the transient visual phenomena reported by patients. Flashes of light (photopsia) and dark, moving lines and specks (floaters) are particularly common occurrences that are usually benign but may signal a retinal tear or detachment. Visual distortion (metamorphopsia) can be the presenting symptom of age-related macular degeneration. Other short-lived disturbances accompany such diverse conditions as migraine, digitalis toxicity, and acute glaucoma. The primary physician needs to know the significance of these visual phenomena and when they presage a serious ophthalmologic or systemic event that requires prompt ophthalmologic attention.

PATHOPHYSIOLOGY AND CLINICAL PRESENTATION (1, 2 and 3)

Floaters

Floaters are vitreous opacities that cast a shadow on the retina. They can be single or multiple, and they characteristically move across the visual field and transiently blur vision if they cross the macula. Their presence is most notable when a person is gazing at a clear, blue sky or blank, white wall. The new onset of floaters may occur as a consequence of vitreous detachment, a retinal tear or detachment, intraocular hemorrhage, or retinal infection.

Vitreoretinal traction is the principal cause of retinal tears and detachments, which can lead to sudden onset of flashes and floaters. As the vitreous gel liquefies with age, its fibrous matrix contracts and pulls away from the retina. Because the vitreous is attached to the retina at several sites, traction can cause tearing that leads to a retinal hole. Detachment may develop by a flow of fluid from the vitreous through the hole and beneath the retina. If the tearing involves a superficial retinal vessel, hemorrhage into the vitreous may occur.

Acute or chronic intraocular inflammation and/or infection are sometimes causes of new floaters, as in the immunocompromised patient with cytomegalovirus (CMV) retinitis. The sudden appearance of one or more floaters suggests the onset of serious underlying pathology. Floaters that are multiple and longstanding are associated with myopia and aging with or without a vitreous detachment.

Flashes (Photopsia)

Flashes (photopsia) are perceptions of bright, small, flickering lights or lightning-like flashes of light. They are most vividly seen in the dark and usually occur with mechanical stimulation of the retina. They account for “seeing stars” when one suffers head trauma or coughs very hard. New onset may be a consequence of vitreous traction on the retina, a retinal tear, or retinal detachment. Just rubbing the eyes can cause similar symptoms. Migraine can cause recurrent episodes of “seeing lights” (scintillating scotoma), although these visual phenomena are more complex and longer lasting. Light flashes may rarely be an indicator of neurologic disease, particularly those affecting the occipital lobe.

Distortion (Metamorphopsia)

Distortion (metamorphopsia) refers to the curvilinear distortion of straight lines or patterns. This visual disturbance is the consequence of an altered shape of the retinal surface, from either a collection of fluid beneath the retina or scarring on the surface. Metamorphopsia is seen with age-related macular degeneration, epiretinal fibrosis, and a variety of ocular diseases that cause traction on the retinal surface and/or retinal scarring.

Zigzag Lines

Migraine can produce a complex set of prodromal visual phenomena that include zigzag lines (sometimes referred to as fortification phenomena) and flashes of light with transient blind spots (scintillating scotoma). These may present with or without a subsequent headache. Typically, the zigzag lines occur adjacent to a gray area of shaded darkness. Both the gray area and the zigzag lines slowly expand. The visual phenomena typically end in 20 to 30 minutes with or without the onset of the headache and leave no residual visual deficit (see Chapter 165).

Halos, Discolorations, and Visual Hallucinations

Halos around lights may be caused by prior corneal refractive surgery, cataracts (usually yellow), implantation of multifocal intraocular lenses at cataract surgery, drug toxicity, and acute glaucoma. Numerous medications can cause halos. The first clinical manifestations of digitalis toxicity may be visual (see Chapter 32) and include lightning flashes, yellow discoloration, halos, and the appearance of frost over objects. Acute glaucoma (see Chapter 207) also produces rainbow-colored halos around lights but not lightning flashes.

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