Hellow guys, Welcome to my website, and you are watching Defects of Vision and their corrections. दृष्टि दोष और उनका सुधार I By Shyamnarayan Sharma #JMS. and this vIdeo is uploaded by JMS Tuition at 2022-05-22T02:12:32-07:00. We are pramote this video only for entertainment and educational perpose only. So, I hop you like our website.
| Name | Defects of Vision and their corrections. दृष्टि दोष और उनका सुधार I By Shyamnarayan Sharma #JMS |
| Video Uploader | Video From JMS Tuition |
| Upload Date | This Video Uploaded At 22-05-2022 09:12:32 |
| Video Discription | Some people can not see things clearly due to loss of accommodation power of the lenses in their eyes. Because of defective refraction by the lenses their vision becomes faint and fuzzy. In general, there are three types of refraction defects. 1. Nearsightedness/ Myopia 2. Farsightedness or hypermetropia 3. Presbyopia _________________________________________________________________________ _________________________________________________________________________ 1. Nearsightedness/ Myopia In this case, the eye can see nearby objects clearly but the distant objects appear indistinct. This means that the far point of the eye is not at infinity but shifts closer to the eye. In nearsightedness, the image of a distant object forms in front of the retina. There are two reasons for this defect. 1.The curvature of the cornea and the eye lens increases. The muscles near the lens can not relax so that the converging power of the lens remains large. 2. The eyeball elongates so that the distance between the lens and the retina increases. This defect can be corrected by using spectacles with concave lens of proper focal length. This lens diverges the incident rays and these diverged rays can be converged by the lens in the eye to form the image on the retina. The focal length of concave lens is negative, so a lens with negative power is required for correcting nearsightedness. The power of the lens is different for different eyes depending on the magnitude of their nearsightedness. 2. Farsightedness or hypermetropia In this defect the human eye can see distant objects clearly but cannot see nearby objects distinctly. This means that the near point of the eye is no longer at 25 cm but shifts farther away. The images of nearby objects get formed behind the retina. There are two reasons for farsightedness. 1. Curvature of the cornea and the eye lens decreases so that, the converging power of the lens becomes less. 2. Due to the flattening of the eye ball the distance between the lens and retina decreases. |
| Category | Education |
| Tags | Defects of Vision and their corrections | Nearsightedness/ Myopia | Farsightedness or hypermetropia |
