What are visual blind spots?

Visual blind spots are areas within the visual field where the vision is absent. They occur naturally due to the way the eye is structured. Specifically, the blind spot is the region on the retina where the optic nerve exits the eye and heads toward the brain. There are no photoreceptors (such as rods or cones) in this spot, which means no visual information is detected from this part of the retina. Each eye has one blind spot located in the central vision, which is usually not noticeable in normal circumstances because the two eyes compensate for one another's blind spots. When one eye is covered, there should logically be a gap in the visual field, but the brain fills in the missing information, based on the surroundings and past experience, to create a complete image.

Microsaccades, tiny, involuntary eye movements, prevent our eyes from fixating on a single location long enough to notice the blind spot. If the eyes were fixed in one position for too long, such as what happens in experiments with paralytics, objects can start disappearing from sight and even lead to hallucinations, although this would normally not happen because of the continuous eye movements.

To demonstrate a blind spot, one can perform a simple experiment with a piece of paper and marks by covering one eye and fixating on one mark, and then moving the paper until the other mark disappears from the visual field. The brain does not typically visually represent this absence of information 1.