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SAI INTERNATIONAL SCHOOL
                                                         Class 8
                                                     Lesson Notes
                                                   Subject-Physics
                                                        CH- Light
                                   Subtopic- Vision defects & Braille system
               Vision Defects:
               Some of the vision defects are as follows:

               Myopia: A person suffering from myopia finds it difficult to see a distant object. This
               disease is also called short sightedness or near sightedness. Spectacles with suitable
               concave lenses can improve the vision in a myopic person.

               Hypermetropia: A person suffering from hypermetropia finds it difficult to see a nearby
               object. This disease is also called long sightedness. Spectacles with suitable convex
               lenses can improve the vision in a hypermetropic person.

               Cataract: The eye lens becomes cloudy in a cataract patient and thus the person
               cannot see clearly. Cataract is treated by surgery. In cataract surgery, the cornea is
               cleaned and an artificial lens is transplanted in the eye.


































               Braille: The resource for visually challenged persons.
                Developed by Louis Braille
                It has 63 dot patterns or characters.
                Each character represents a letter, a common word or a grammatical sign.
                Dots are arranged in two vertical rows of three dots each.


               Suggested Activity
               Check the difference in spectacle lenses used by a young person and an elderly person.
               What can you guess about the type of vision defect they are having?
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