Understanding the Human Eye: Structure, Function, and Light Perception
This chapter delves into the fascinating physics of the human eye, exploring how light, an electromagnetic radiation, is perceived through its intricate structure. We discuss the critical role of the three layers of the eye: the fibrous tunic, vascular tunic, and retina, as well as the function of key components like the cornea, lens, and photoreceptors. Learn about the importance of wavelength, image formation, and common vision problems such as presbyopia and astigmatism. Discover how eye muscles enable movement and the protective roles of eyelids and tears.
Understanding the Human Eye: Structure, Function, and Light Perception
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Presentation Transcript
Chapter 2 The Human Eye
Physics Review • Light • Electromagnetic radiation • Wavelength determines quality • Measured in nanometers • Why light? • Reliable: Travels very fast and straight • Prevalent: Lots of it • Informative: Reflected/Absorbed by surface molecules
The Head • Eye placement: • Lateral vs. Frontal • Skull: Orbit • Eye Movement • 6 extra-ocular muscles: • Conjugate: move together • Vergence: move opposite • Eyelids: • Protection and moisture • Blinking and Distance • Tears
Eye Function • Image: light distribution that preserves the spatial ordering of locations in space • Image formation – reversing light divergence • Optical power of: • 1) cornea: 2/3rds of eye’s optical power • 2) lens: flexing called accommodation
Eye Structure • Three layers: • Protecting: Fibrous Tunic • Nourishing: Vascular Tunic • Detecting: Retina
Fibrous Tunic • Sclera – “white” of eye, dense material, gives eye it’s shape • Cornea – transparent “bulge”, allows light into eye
Problems with Lens • Presbyopia: • loss of sight with age • Astigmatism: • Distortion of cornea
Vascular Tunic • Choroid • Pigment epithelium • Contains blood vessels and capillaries • Reduces light scatter and disposes of waste • Anterior Chamber • Manufactures aqueous humor • Contains: • Iris/Pupil • Lens
Retina • Contains photoreceptors • Landmarks: • Macula (1.5mm diameter): focus of eye, contains fovea • Optic Disk: “blind spot”
Photoreceptors • Order of stimulation:
Photopigments • Two components • Opsin: large protein, 3 types • Retinal: from vitamin A • Phototransduction