3. Emmetropia
The emmetropic eye is normal eye
Emmetropic eye parallel rays of light come to
focus on the retina
4. Ametropia
Ametropia (Refractive error)
Mismatch between axial length and refractive
power Parallel light rays don’t fall on the retina
(no accommodation)
Hyperopia { hypermetropia }
Myopia
Astigmatism
5. Hyperopia {Hypermetropia}
The parallel rays coming from infinity focus at
point behind the retina( unaccommodative
eye)
Axial hyperopia
Curvature hyperopia
Latent hyperopia
Manifest hyperopia
Absolute hyperopia
6. To Understand
A 32 year old man have vn of 6/18
With+ 1.00 D improves vn 6/6(Absolute
hyperopia)
If an additional+1.50D patient can still see 6/6
(manifest hyperopia)
With cycloplegic +3.50D vn 6/6
So 1.00D is latent
7. Symptoms and treatment
Young may not cause symptoms
Eye strain
Headaches
Earlier presbyopia
On demand to correct with convex lenses
Spectacle
Contact lens
Surgery
8. Myopia
Is near-sightedness is that condition on in
which parallel rays of light come to focus at
point just in front of the retina
Axial myopia
Curvature myopia
Index myopia
9. Symptoms And Treatment
Inability to see objects clearly at distance
Squeeze eyes
Burning sensation
To correct with concave lens
Spectacle
Contact lens
Surgery
10. Astigmatism
Astigmatism is the condition in which rays of
light are not refracted equally in all directions
so that point focus on the retina is not attained
Regular astigmatism
Irregular astigmatism
11. Regular Astigmatism
Regular astigmatism is that refractive condition
in which the axes of the principal meridians of
the astigmatism are right angles to each other.
Types:
• Simple Astigmatism
• Simple Hyperopic / Myopia Astigmatism
• Compound Hyperopic / Myopic Astigmatism
• Mixed Astigmatism
13. Irregular Astigmatism
It is a refractive condition in which excess of
the principal meridian are not right angle to
each other.
If the cornea has damaged by Trauma or
inflammation or scar tissue.
Irregularity of the corneal surface.
14. Symptoms and treatment
Blurred vision
Eye strain
To correct with concave/convex cyl
Spectacle
Contact lens
Surgery
16. Symptoms and treatment
Inability to do near work
Some patient complain that they have to hold
the print farther away
Fatigue
Trouble with Threading a needle
To correct with convex lens
Spectacle
Contact lens
17. Visual Age consideration for
Presbyopic
At the ages 42 to 45----+1.00D to +1.25D
At the ages 45 to 50----+1.50D to +1.75D
At the ages 50to 65----+2.00D to +3.00D
18. Aphakia
Is a condition in which the crystalline lensis
absent from the eye
May be caused by removal of cataract lens or
displacement of the lens
To correct with convex lens
Spectacle
Contact lens
Surgery
19. Kept in mind
The optical centers
must be exact
Vertex distance
Lanticular aphakic
lens
The frame must fit
comfortably on the
nose and to b set
straight