"VISION DEFECTS AND THEIR CORRECTIONS" MYOPIA:(short sightedness) person can see near objects but can not see far object. *image of far off objects is formed in front of retina and hence it appears blurred. *corrected by using a concave lens. HYPERMETROPIA-a person suffering can see distant objects clearly but can not see nearby objects clearly. *in this defect the image of the nearby objects falls behind the retina. *corrected by convex or converging lens. PRESBIOPIA(in this defect,a person can neither see the near objects clearly nor the distant objects) *corrected by bifocal lens(lower part of lens is convex and upper part is concave) ASTIGMATISM: in this defect, a person can not distinctly see the horizotals and vertical lines. *corrected by cylindrical lens. NIGHT BLINDNESS(DUE TO VIT. A DEFICENCY)
Posted on: Mon, 01 Jul 2013 06:15:34 +0000