Illusory palinopsia

Illusory palinopsia
Palinopsia simulation
Specialty	Ophthalmology

Illusory palinopsia is a subtype of

Prolonged indistinct afterimages are unformed and occur at the same location in the visual field as the original stimulus. Stimulus intensity, contrast, and fixation length affects the generation and severity of these perseverated images. For example, after seeing a bright light such as a car headlight or a camera flash, a persistent afterimage remains in the visual field for several minutes.^[5] Patients often report photophobia, which can restrict their ability to perform outdoor activity. The prolonged image or light is typically isochromatic (positive afterimage) to the original stimulus, but can fade to different colors over time.^[7] Afterimages from lights tend to last longer than the indistinct afterimages from other brightly colored objects. Palinoptic prolonged light afterimages of the complementary color are differentiated from physiological afterimages based on afterimage intensity and duration.^[2][8]

Light streaking

Light streaking describes a comet-like tail which is seen due to motion between a person or a light.^[4] The streaking usually persists for several seconds before fading and often occurs with bright lights on a dark background. Patients commonly report of difficulty with night driving since the headlights of oncoming cars cause multiple streaks which obscure vision.^[5]

Visual trailing

Visual trailing describes an object in motion leaving frozen copies in its wake.^[9][10] These motion-induced afterimages may be discontinuous such as in a film reel or may be blurred together such as in a long-exposure photograph. If discontinuous, the patient also usually reports akinetopsia. The perseverated images last a few seconds and are usually identical in color and shape to the original stimulus. Most cases describe visual trails during movement of an object, although there are also reports from the movement of the observer's head or eyes.^[6]

Variant image perseveration

There are a few cases of palinopsia with many of the same features as hallucinatory palinopsia (formed image perseveration) but with some important differences. The formed perseverated image may only last a couple seconds^[11] or may be black or translucent.^[12] These variants usually lack the realistic clarity of hallucinatory palinopsia, and the generation of the palinoptic images is affected by fixation time, motion, stimulus intensity, or contrast. These variants probably represent an overlap in hallucinatory and illusory palinopsia but are included in illusory palinopsia since they often co-exist with the other illusory symptoms.

Cause

Of the published cases of palinopsia that are

Palinopsia necessitates a full ophthalmologic and neurologic history and physical exam. There are no clear guidelines on the work-up for illusory palinopsia, but it is not unreasonable to order automated visual field testing and neuroimaging since migraine aura can sometimes mimic seizures or cortical lesions.^[25] However, in a young patient without risk factors or other worrisome symptoms or signs (vasculopathy, history of cancer, etc.), neuroimaging for illusory palinopsia is low-yield but may grant the patient peace of mind.^[2]

The

Due to the subjective nature of the symptoms and the lack of organic findings, clinicians may be dismissive of illusory palinopsia, sometimes causing the patient distress. There is considerable evidence in the literature confirming the symptom legitimacy, so validating the patient's symptoms can help ease anxiety. Unidirectional visual trails or illusory symptoms confined to part of a visual field suggest cortical pathology and necessitate further work-up.^[26][27][28]

Treatment

There is limited data on treating the visual disturbances associated with