Blindness is the condition which is generally caused due to the lack of visual perception which is either caused due to physiological or due to certain psychological factors. Sense organ eye and the spinal cord work together in the process of visualization. The cornea, the lens, the iris and the retina all works together as centers of light and of viewing images. When the true contact between the eyes and the brain is absent, it may lead to the blindness in a person.
Sometimes even a blind person can experience the shadows and light which can be termed as partial blindness. There are various scales which have been developed in order to describe the amount of loss of vision or blindness. The complete lack of appearance and lack of perception to light is clinically termed as total blindness or termed as "NLP", which means "no light perception". "Blindness" is basically used to describe certain forms of severe impairment of vision.
Lack of proper perception to color may lead to color blindness. Color blindness often makes a person unable to perceive the basic differences between colors. Color blindness may cause due to eye, nerve, or brain damage or it may also be the cause of exposure to certain chemicals. Red, blue, and green are generally the three types of color receptors which is located in the eyes. Black and white are also certain other forms of color. Lack of one or either two types of color receptors lead to the cause of color blindness. For instance, Red and green are considered as the most common color preceptors. Thus lack of either red or green or red and green together may lead to color blindness. Complete color blindness is however very rare though partial forms of color blindness are common.
Inability to see in dim light or darkness causes night blindness. Night blindness is not only a disorder but also a symptom of underlying disorder or problem. Night blindness causes various eye diseases. Night blindness may occur from birth, or may occur due to certain injury or malnutrition in one's diet. Night blindness often leads to difficulty when driving at night, poor vision in low light, etc. Night blindness is generally caused due to a disorder of the cells in the retina which is responsible for vision in dim light.