1. Optical defects & Abnormalities วัตถุประสงค์ ...
อธิบายการเกิดและวิธีแก้ไขสายตาสั้น สายตายาว สายตาเอียง
และ สายตาวัยชราได้

2. Optical Defects & Abnormalities
- Optical defects of the emmetropic eye
Spherical & chromatic aberration
Spherical aberration. A perfect lens (top) focuses all incoming rays to a point on the optic axis. A real lens with spherical surfaces (bottom) suffers from spherical aberration: it focuses rays more tightly if they enter it far from the optic axis than if they enter closer to the axis. It therefore does not produce a perfect focal point. (Drawing is exaggerated.)
Spherical aberration
Chromatic aberration of a single lens causes different wavelengths of light to have differing focal lengths

3. Optical Defects & Abnormalities
- Ametropia
- Causes: axial length, corneal refraction, separation of cornea & lens
- Types:
Myopia
Hyperopia (hypermetropia)
Presbyopia
Astigmatism

4. Optical Defects & Abnormalities
Astigmatism, demonstrating that light rays focus at one focal distance in one focal plane (plane AC) and at another focal distance in the olane at a right
angle (plane BD).
A, Point focus of parallel light rays by a spherical convex lens.
B, Line focus of parallel light rays by a cylindrical convex lens.

5. Resources : Handout : Vision Textbooks : 3. Formative evaluation II
 - Barrett KE, Barman SM, Boitano S and Brooks HL. Ganong's Review
of Medical Physiology, 25th ed., McGraw-Hill Education, [e-book]
Koeppen BM and Stanton BA : Berne & Levy Physiology, 6th ed.,
Mosby-Elsevier, 2010.
 - Widmaier EP, Raff H and Strang KT : Vander’s Human Physiology,
The mechanism of body function, 11th ed., McGraw-Hill, 2008.
3. Formative evaluation II