What Is Palinopsia?
Palinopsia is a group of visible symptoms in which there is an abnormal recurring or persisting image in time, even when the view's stimuli are removed. Palinopsia is derived from the Greek word “palin,” meaning again, and “opsia,” meaning seeing. Palinopsia is classified into two primary types: hallucinatory palinopsia and illusory palinopsia. Palinopsia could be the presenting sign of a potentially fatal posterior cortical lesion or a side effect of certain medications.
Palinopsia is different from afterimages, a normal response to an image that persists for a short time after a person has stopped looking at the visual stimulus. In contrast, palinopsia images are more intense and long-lasting than physiological after-images and may appear immediately or after a time interval.
Also, palinopsia images are positive or present with similar colors to the original visual stimulus. Still, physiological after-images are present as negative images or complementary colors of the visuals.
What Are the Types of Palinopsia?
Palinopsia is classified into two primary types: hallucinatory palinopsia and illusory palinopsia.
Hallucinatory Palinopsia:
Hallucinatory palinopsia is a type of palinopsia that causes visualization of a previous image, even after removing the stimulus. These images can be simple, like colors, lines, and shapes, or complex, like specific objects, people, animals, or scenes. The afterimages caused by hallucinatory palinopsia are usually high-resolution but can also vary. Hallucinatory afterimages generally last for a short time, like a few seconds or minutes. They are not influenced by external factors such as motion or light. They are caused mainly by seizures or posterior cortical lesions and signify a problem with visual memory. However, in some cases, they can linger for hours.
Illusory Palinopsia:
Migraines, certain medications, illicit drugs, head trauma, or a defect in visual perception cause illusory palinopsia. Illusory palinopsia and optical illusions share many similarities. The afterimages of illusory palinopsia are blurry, unformed, or low resolution. These images are influenced by motion or light.
What Are the Causes of Palinopsia?
The exact causes of palinopsia are still unclear as it is rare. Hallucinatory and illusory palinopsia does offer some information about what is causing palinopsia. However, even more research is needed to understand the causes clearly.
Hallucinatory Palinopsia - Hallucinatory palinopsia mainly occurs due to some disturbances within the brain’s ability to store visual stimuli that create clear, long-lasting, and moving images. They can happen anywhere in the vision field. It often occurs as a sign of a brain-related condition, such as posterior cortical lesions or seizures, rather than to outside factors.
Posterior cortical lesions associated with hallucinatory palinopsia are:
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Bleeding occurs in strokes when a blood vessel in the brain bursts.
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Arteriovenous malformations, when there is a tangle between the blood vessels in the body).
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Neoplasms (abnormal tissue masses growth inside the brain).
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Infarctions occur due to tissue death or injury when blood flow is lacking.
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Aneurysm (a ballooning or bulge at a weak spot of a blood vessel).
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Abscesses (masses usually caused by an infection).
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Tuberculomas (a rare tumor-like growth but a severe form of tuberculosis).
Hallucinatory palinopsia that is caused by seizures may have various metabolic issues, such as:
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Hyperglycemia (high blood sugar).
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Ion channel issues.
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Creutzfeldt-Jakob disease (a rare disorder causing brain cells to break down).
Illusory Palinopsia - Illusory palinopsia is associated with outside stimuli like lighting and movement. The exact cause of illusory palinopsia is not clear but, there have been proven that these conditions can cause palinopsia:
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Changes in the neurotransmitters involved with migraines.
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Hallucinogen persisting perception disorder (HPPD).
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Psychedelic drugs such as Marijuana, Mescaline, and Ecstasy.
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Medications such as Trazodone, Risperidone, Nefazodone, Mirtazapine, Topiramate, and Clomiphene.
What Are the Symptoms of Palinopsia?
Palinopsia usually has visual field disturbances, and these disturbances more commonly affect the left side eye, which reflects the significance of posteriorly placed, right-sided cerebral lesions. Apart from visual field disturbances, a number of other clinical features may be present.
There are eight subcategories of symptoms, which includes:
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Formed Image Preservation - High resolution, realistic images fixed in the patient's vision for seconds to days.
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Scene Preseveration - A scene similar to a video clip that continuously replays in the vision.
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Categorical Incorporation - An image of an object that superimposes an image, object, or person.
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Light Streaking - A streak of the image is visualized when seeing a bright object against a dark background. For example, while driving at night.
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Visual Trailing - Multiple images appear in a trail behind a moving object.
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Variant Image Preservation - Low-resolution images affected by rapid external movements.
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Illusory Visual Spread - Spread of visual pattern into other objects in the visual field.
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Prolonged Indistinct Afterimages - Images are seen in the same place of the patient's visual field as the original one.
Other associated symptoms of palinopsia include:
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Cerebral polyopia (seeing two or more images arranged in ordered rows or columns after an object fixation).
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Akinetopsia (loss of ability to perceive visual motion).
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Visual allesthesia (transposition or rotation of the visual field).
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Entoptic phenomena (visual experiences derived from within the brain or eye).
How Is Palinopsia Diagnosed?
To find out whether a patient has hallucinatory or illusory palinopsia, a physician will take a full brain and eye history, and a physical exam will be done. The following test will be performed
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Automated Visual Field Testing - It helps detect illusory palinopsia conditions and causes.
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Neuroimaging - It is performed in people with hallucinatory palinopsia as its effects can indicate severe neurological diseases.
How Is Palinopsia Treated?
Treatment for palinopsia will depend on its type and cause.
Illusory Palinopsia - The treatment for illusory palinopsia can involve medications that reduce the excitability of neurons, such as Clonidine, Acetazolamide, Gabapentin, magnesium, or calcium channel blockers. More studies are needed to check the effectiveness and efficacy of the drug. Wearing contact lenses and sunglasses will help reduce symptoms of illusory palinopsia. Treating migraines will be beneficial for people who have illusory afterimages from their migraines.
Hallucinatory Palinopsia - It usually occurs due to some underlying serious neurological problems. Treating the underlying cause is usually beneficial in resolving palinopsia.
Conclusion:
Palinopsia is a visual condition in which images of an object reappear even after an individual has stopped looking at the object. Generally, patients with palinopsia see repeated images of the object. Depending on the type of palinopsia, the causes and treatment vary. In some people, medications will be helpful, while in others, treating underlying neurological conditions will help in treating the condition.
