1. Refractive errors

2. Refractive surfaces of the eye
Cornea : main
Lens : accommodation

3. emmetropia
With accommodation completely relaxed parallel rays will come to point focus on the retina

4. Myopia
With accommodation completely relaxed parallel rays will come to point focus in front of the retina
Axial
Refractive
Concave spherical

5. Hypermetropia
With accommodation completely relaxed parallel rays will come to point focus behind of the retina
Axial
Refractive
Convex spherical

6. Astigmatism Parallel rays dose not come to point focus Line focus
Cylindrical error

7. presbyopia Loss of accommodation Difficulty in near vision
Bifocal or multifocal lenses

8. Refractive surgery Incisional Photorefracrtive corneal surgery ICL
Clear lens extraction

9. Thank you