Tag: disorders of nervous system

• Cones are the photoreceptor cells that contain iodopsin, porpyrosin and cyanopsin pigments. These cells are associated with the daylight vision and colour vision of eyes.
  
• Rods are the photoreceptor cells that contain rhodopsin pigment and associated with scotopic vision of eye i.e. vision under low light.
• Rhodopsin or visual purple (derivative of vitamin A) is a photopigment in the rods that are associated with scotopic vision of eye i.e. vision under low light or dim light.

The old person requires spectacle for both nearsightedness and farsightedness which is found in presbyopia for correcting near vision and far vision both.

Presbyopia is a condition of consisting of nearsightedness, farsightedness, and astigmatism. The condition is common in old age because of hardening of eye lens which results in focusing of light behind the retina for closely placed objects.

• Braille is named after its creator, Louis Braille, and consists of raised dots arranged in "cells."
•  A cell is made up of six dots that fit under the fingertips, arranged in two columns of three dots each. 
• Each cell represents a letter, a word, a combination of letters, a numeral or a punctuation mark. Hence, In braille script, letters are formed with 6 embossed dots.

Helen Adams Keller was born a healthy child in Tuscumbia, Alabama, on June 27, 1880. At the age of 19 months, Helen became deaf and blind as a result of an unknown illness, perhaps rubella or scarlet fever. As Helen grew from infancy into childhood, she became wild and unruly.As she so often remarked as an adult, her life changed on March 3, 1887. On that day, Anne Mansfield Sullivan came to Tuscumbia to be her teacher. Anne began her task of teaching Helen by manually signing into the child's hand. Anne had brought a doll that the children at Perkins had made for her to take to Helen. By spelling "d-o-l-l" into the child's hand, she hoped to teach her to connect objects with letters. Anne took Helen to the water pump outside and put Helen's hand under the spout. As the cool water gushed over one hand, she spelled into the other hand the word "w-a-t-e-r" first slowly, then rapidly. Suddenly, the signals had meaning in Helen's mind. She knew that "water" meant the wonderful cool substance flowing over her hand. Quickly, she stopped and touched the earth and demanded its letter name and by nightfall, she had learned 30 words.