Ametropia-defective eyesight due to focusing, Physics

Defective eyesight due to focusing(refractive)problems- ametropia:


It is often possible to correct ametropia completely with glasses

There are four general types of ametropia:

  • Myopia (near sightedness) ,hyperopia or hypermetropia (far sightedness), astigmatism(asymmetrical focusing) and presbyopia (old sight) fig(2)  .

418_Ametropia-Defective eyesight due to focusing.png

 

 

2004_Ametropia-Defective eyesight due to focusing 2.png

 

  • The myopic individual usually has too long an eyebellor too much curvature of the cornea , distance objects come to focus in front of the retina, and the rays diverge to cause a blurred image at the retina .This condition is easily corrected with negative lens.
  • A hyperopic eye has a near point further away than normal and use some of its accommodation to see distance objects clearly ,the usual cause of  hyperopic is too short eye ball , a positive lens is used to correct this condition fig(3).
  • Inastigmatism ,the curvature of the cornea is uneven .Astigmatism cannot be corrected by a simple positive or negative lens, it is corrected with an  asymmetric lens in which the length is greater in one direction than in the perpendicular direction.

 

875_Ametropia-Defective eyesight due to focusing 3.png

Posted Date: 10/1/2012 9:09:18 AM | Location : United States







Related Discussions:- Ametropia-defective eyesight due to focusing, Assignment Help, Ask Question on Ametropia-defective eyesight due to focusing, Get Answer, Expert's Help, Ametropia-defective eyesight due to focusing Discussions

Write discussion on Ametropia-defective eyesight due to focusing
Your posts are moderated
Related Questions
Explain Chemical Potential of Ideal Gas? Derive the expression for the chemical potential and Gibbs free energy of N molecules of an ideal gas at temperature T, pressure P and


#question-the measurement of 30.43 degrees north of east..


A 10 kg block slides down a smooth inclined surface as shown in Figure 1. Determine the terminal velocity of the block if the 0.1 mm gap between the block and the surface contains

How fast would the train be travelling when it in Lac-Mégantic derailed. There were 5 locomotives and 72 cars filled with 113,000 litres of crude oil. The elevation was 520 m Cote


Write the expetiment of vernier caliper?

(a) A 400mm length of conductor carrying a current of 25A is situated at right-angles to a magnetic field among two poles of an electric motor. The poles have a circular cross

(1) Standing pulse can be longitudinal / transverse. (2) The disturbance confined to a particular part among the starting point and reflecting point of the ray. (3) There is