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

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

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

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.

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, 2016. [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