Chapter 2Chapter 2The Human Eye

Physics ReviewPhysics ReviewLight: Electromagnetic radiation

◦ Wavelength (nm) determines quality◦ Why light?

Reliable Prevalent Informative

The HeadThe HeadEye placement:

◦ Lateral vs. Frontal

Skull: OrbitEye Movement

◦ 6 extra-ocular muscles: Conjugate Vergence

EyelidsTears

Eye FunctionEye FunctionWhat is an image?Image formation = reversing light

divergence◦Optical Power of…

1) cornea: 2/3rds of optical power 2) lens: accommodation

Eye StructureEye StructureThree layers:

◦Protecting: Fibrous Tunic◦Nourishing: Vascular Tunic◦Detecting: Retina

Fibrous TunicFibrous TunicSclera

Cornea

Out of FocusOut of FocusCondition Common

nameEye Shape

Location of focus

Lens needed

Myopic Nearsighted

Too Long In front of retina

Concave

Hyperopic Farsighted Too Short Behind retina

Convex

Emmetropic

Normal Normal On fovea None

Problems with LensProblems with LensPresbyopia: Astigmatism

Vascular TunicVascular TunicChoroid

◦Pigment epithelium

Anterior Chamber◦Aqueous humor◦Lens and pupil

GlaucomaGlaucoma

RetinaRetinaPhotoreceptorsLandmarks:

◦ Macula◦ Optic Disk

PhotoreceptorsPhotoreceptors

Paul Bunyan Ate His Rice

PhotopigmentsPhotopigmentsTwo components

◦Opsin: large protein, 3 types◦Retinal (vitamin A)

Phototransduction

Opsin

Retinal

Wavelength SensitivitiesWavelength Sensitivities

Cell Most Sensitive Wavelength

Relative “color”

Rods 500 nm Bluish-green

Cones440 nm Violet530 nm Green560 nm Yellow