Table of contents:
- What is palinopsia?
- Know the types of palinopsia
- Various symptoms of palinopsia based on the type
- What causes us to see a palinopsian black shadow?
- What checks should be done?
Shadow appears when light is blocked by an object. Try to stand with your back to the sun. Then, your silhouette will fall right in front of your body. As you move away from the light, your shadows will shrink and disappear. But if you still see black shadows even after the object blocking the light source has moved far away, you need to be alert. No, suddenly seeing a black shadow doesn't mean you are seeing a ghost. This could be a sign of a medical condition called palinopsia.
What is palinopsia?
Palinopsia is a term to describe visual disturbances characterized by the appearance of visual illusions, causing a person to see black images continuously or repeatedly for several minutes after the actual object disappears.
The term palinopsia has its roots from Ancient Greek which means "to see again" ("palin"Which means" again "and"opsia " which means seeing).
Know the types of palinopsia
Palinopsia can be divided into two types, based on the conditions experienced. The first is hallucinatory palinopsia which is characterized by the formation of a visual illusion, it can be simple (light, line, color) or complex (animal, object, human), without any influence from the surrounding environment, usually occurs in high resolution. For example, after seeing a cat, the silhouette of the cat that was previously "stuck" in your field of view.
Hallucinatory illusions are usually temporary and brief only from a few seconds to a few minutes). But in some cases the black shadow may last for hours. This type of palinopsia is also known as afterimage.
The second type is palinopsia illusori. Illusory palinopsia is the formation of a visual image with a shape that is usually imperfect and in low resolution. The onset of this type of palinopsia is related to movement and light in the environment. That's why people with palinopsia ilusori can see the flash of a comet-like tail behind a moving object leaving light.
Illusory palinopsia is caused by an abnormality in how the eye forms the initial perception of an object. Meanwhile, hallucinatory palinopsia is caused by abnormalities after the object is recorded in visual memory.
Various symptoms of palinopsia based on the type
There are several forms of symptoms that can be complained of, including:
- Seeing a black shadow that remains in the field of vision. The images of these objects are the same as real objects that have been seen before, including from their clarity, color, and resolution. So, what is chosen is not always a black shadow. It could be a duplicate of a person or object that we saw earlier, like a hologram.
- Scenes that repeat for several minutes. For example, if someone sees the scene of combing hair, a few moments later he will be able to return to see the scene when his view has shifted. This can happen over and over again.
- Categorical fusion, which is when object A is seen impinging on other objects around it. Suppose a person saw the mustache of person A, he would see the same mustache on everyone else around him.
- The line that appeared behind the light and persisted for a few seconds before finally disappearing. This causes difficulty in driving a car especially at night.
- Visual footprint, which is when the same object follows an object in front of it that is moving. Generally, the image of the object being seen will have the same shape and size, but with a lower color intensity. This is often described as "The Matrix”.
What causes us to see a palinopsian black shadow?
Palinopsia can arise due to various things, ranging from dangerous diseases to the result of using certain drugs. Therefore, seeing black shadows (especially if they occur repeatedly) cannot be underestimated, let alone considered as a mystical thing.
Several causes of palinopsia, including:
- Brain tumor
- Impaired arterivena formation
- Epilepsy
- Early symptoms of stroke
- Severe impact on the head area injuring the brain (cerebral infarction, abscess)
- Migraine
- Medicines (trazodone, topiramate, ecstasy, and LSD)
What checks should be done?
Various types of examinations must be carried out to determine the cause of the onset of palinopsia. The examination to be carried out depends on the complaint and also the possibility of the disease being suffered.
An ophthalmologist will generally begin the examination by examining visual acuity, eye movement, examining visual field disorders, and examining the condition of the front chambers of the eye.
Other advanced examinations such as neurological imaging using MRI, blood tests, electroensefalogram (EEG), and drug use screening will be carried out according to the instructions obtained from the initial examination.
