Many people assume that individuals who are “totally blind” experience nothing but absolute darkness. However, the reality of what totally blind people perceive is far more varied and complex, challenging this simplistic understanding.
Understanding “Total Blindness”
The term “total blindness” is not a singular experience, but rather a medical or legal classification. Medically, total blindness is often defined as having “no light perception” (NLP), meaning an individual cannot detect any light. However, even within this definition, some individuals with NLP still report being able to discern whether a room is light or dark, or experiencing flashes of light.
Legally, in the United States, “legal blindness” is defined by a corrected visual acuity of 20/200 or less in the better eye, or a visual field of 20 degrees or less. This means what a person with normal vision can see at 200 feet, a legally blind person can only see at 20 feet. Only about 15% of people with eye disorders are considered totally blind, with the majority having some residual vision.
The Spectrum of Visual Perception
For those truly without light perception, the experience is often described as “nothingness,” rather than blackness, as they lack any prior visual reference for color or darkness. This state is distinct from simply closing one’s eyes, as it involves a complete absence of visual input.
Many individuals classified as totally blind still possess some level of light perception. They might be able to distinguish between light and shadow, or perceive the movement of light. For example, they may be able to tell if a light is on or off in a room, or sense the presence of sunlight or camera flashes.
A phenomenon known as Charles Bonnet Syndrome (CBS) can occur in individuals who have experienced significant vision loss, particularly later in life. This condition involves vivid, complex visual hallucinations, which can include recognizable shapes, random patterns, or colors. These “phantom visions” are not indicative of mental illness but are a neurological response to the brain’s attempt to fill in missing visual information.
The Brain’s Reorganization
The human brain exhibits remarkable neuroplasticity, adapting in response to experience or injury. In individuals with total blindness, particularly those born blind, areas of the brain typically dedicated to processing visual information may be repurposed for other sensory inputs. This reorganization can lead to heightened abilities in other senses, such as hearing, touch, and smell.
For instance, the visual cortex, normally responsible for sight, might become active when a blind person reads Braille or processes auditory information. This cross-modal plasticity allows the brain to compensate for the absence of visual input by enhancing the processing capabilities of remaining senses.
Dreams and Mental Imagery
The experience of dreams and mental imagery in totally blind individuals varies significantly depending on whether their blindness is congenital (present from birth) or acquired later in life. Individuals born blind do not experience visual dreams or form mental images based on sight. Their dreams are instead rich with sensations from their other senses, such as sounds, tactile sensations, smells, and emotions.
Conversely, those who lost their sight later in life often continue to have visual dreams and can form mental images based on their past visual experiences. These visual dream experiences can even extend to people and objects they encountered after the onset of blindness, drawing upon their visual memories to construct new scenarios.