Cognitive illusions:

Cognitive illusions and its categories:

It is believed that cognitive illusions arise from interactions with perceptions about the world, leading to "unconscious inferences", an idea first suggested by the German physicist and physician Hermann Helmholtz in the 19th century. Cognitive illusions have been categorized into distorting illusions, fiction illusions or paradox illusions, ambiguous illusions.

• Objects or pictures that highlight a perceptual “switch” between the alternative interpretations are known as ambiguous illusions. One of the most famous examples of this is Necker Cube; Other examples are the Rubin vase and "Squircle" based on Kokichi Sugihara's obscure cylinder illusion.
• Impossible object illusions which is another name of paradox illusions are produced by the objects that are impossible or paradoxical, for example, impossible staircase or Penrose triangle seen for example, in M.C. Escher’s Descending and Ascending and Waterfall. Triangle is an illusion that relies on a cognitive misconception that adjacent edges must join. The pfg precision optics have collaborated with spherical lens manufacturer available in the market in order to manufacture high efficency flat optics.
• Distorting or geometrical-optical illusions are divided on the basis of the length, position, size, or curvature. An exact example is the illusion of a cafe wall. There are some other famous examples which include the famous Ponzo illusion and the Müller–Lyer illusion.
• Fictions take place when a figure is observed even though it is not in the stimulus.

Pathological visual illusions:

Pathological visual illusions can be defined as the distortion or disturbance of a real external stimulus and are commonly persistent and diffuse. Most commonly, pathological visual illusions are usually occurred throughout the visual field, therefore suggesting sensitivity alterations or global excitability. On the other hand, visual hallucinations are basically the perception of an external visual stimulus where nothing exists. In most common, visual hallucination takes place because of the focal dysfunction and is usually transparent.

Types of visual illusions include oscillopsia, halos around objects, delusional palinopsia (visual training, streaks of light, long blurry post-images), akinetopsia, visual snow, micropsia, macropsia, teleopsia, pelopsia, metamorphosis, dyschromatopsia, intense flashes, Including a blue area, entopic events are involved, and Purkinje trees. The etiologies associated with pathological visual illusions include a variety of ocular diseases, migraines, hallucinations, persistent perception disorders, head trauma, and prescription drugs. If medical treatment does not find out the reason behind the pathological visual illusions, the disturbances in idiopathic visual could be analogous to the changed excitability state seen in visual aura with no migraine headache.