For paramedics students

1. Presentator: Duaa Fatima
(Optometrist)

2.  Refraction is defined as the change in
direction of light as it passes from one
medium to other of different densities.
 Refractive index is the ratio of speed of light
in vaccum to speed of light in medium.
 formula: n=c/v
 Examples: air=1
 Cornea=1.37
 Lens=1.86

3.  EMMETROPIA:
It is the state of eye in which parallel rays of light focus
on the retina without any accomodative effort.
 AMETROPIA:
It is the state of eye in which parallel rays of light are
unable to focus on the retina and to produce clear
image.

5.  Myopia
 Hypermetropia
 Astigmatism
 Anisometropia

6.  It is the state of eye in which parallel light right rays
after entering in the eyes focus in front of retina and
unable to produce clear distant image.

7. Types of myopia:
 Axial myopia( in case of posterior staphyloma)
 Refractive myopia(in case of nucleosclerosis)
Grades of Myopia:
 Mild myopia (till -1.5D)
 moderate myopia (1.5D-6.0D)
 High myopia (6.0D or more)
 Pathological myopia (more than 8.0D)

8.  It is the state of eye in which parallel rays of light are
focused behind the retina that results in blurr image
of near object.
 Overall refractive power of eye is less.

9.  Manifest Hypermetropia
 Latent hypermetropia
On the basis of accomodation:
 Facultative
 Absolute
Grading of hypermetropia :
 Low (till 2.0D)
 Moderate (2.25D-5.0D)
 High(5.25D or more)

10.  It is the state in which eye varies in power in
different meridians.
 Image is formed at Sturm’s conoid.

11.  Simple myopic astigmatism
One line focus on retina and other infront of retina
 Simple hyperopic astigmatism
One line focuson retina and other behind the retina.
 Mixed astigmatism
One line focus infront of retina and other behind the
retina

12.  It is the state of eye in whiich each eye has different
refractive power that may result in amblyopia and
strabismic eye.

13. Refractive errors can be corrected by:
 Objective refraction
 Subjective refraction
 Post refraction tests

14.  Spectacles
 Contact lens
 Refractive surgery
 Intra corneal lens implantation
 Clear lens extraction
 orthokeratology