Chapter 10

Vision Basic Structure –Outer –Middle –Inner tunics Outer tunic –Cornea Transparent anterior portion membrane Window of the eye Helps focus entering light ryas Non-vascular Cut to correct imperfections Worldwide: Blindness is most common by changes in the cornea. Lack of corneal donor tissue is the main reason people fail to undergo corneal transplants.

Vision Outer Tunic –Sclera White of the eye Protection and attachment for extrinsic muscles –Optic Nerve Conducts impulses Middle Tunic –Choroid coat Vascular layer Melanocytes that absorb excess light

Vision Middle Tunic –Lens Transparent capsule (Suspensory ligaments hold it in place and control the shape of the capsule.) Convex or concave Accommodation –Adjustment of the lense thickness to make close vision possible Cataract treatment usually involves removal of the lens

Vision Middle Tunic –Ciliary Body 2 sets of ciliary fibers. Hold suspensory ligaments The lens of the eye thickens when the ciliary muscles contract. –Iris A diaphragm smooth muscle Divides the area into two chambers –Anterior – cornea and lens –Posterior- iris-lens By action controls the size of the pupil of the eye

Vision Middle Tunic –Aqueous Humor The fluid secreted by the ciliary body into the posterior chamber. Fills the space between the cornea and the lens. Circulates into the anterior chamber –Maintains the shape of the front of the eye Glaucoma is usually caused by excessive amounts of aqueous humor.

Inner Tunic Retina –Photoreceptic layer of the eye Visual receptor cell-photoreceptor –Contains the rods and cones of the eye –Thin layer area rods Night or dim light vision –More sensitive to light than cones –Cones Color vision/ sharp vision

Inner Tunic Fovea Centralis –Region of sharpest vision within the retina lacks rods but is packed with cones Optic Disk –Region within the retina lacking any receptors Blind spot Rhodopsin –Visiual purple –Light sensitive pigment located within the rods –Contains rods and cones Receptor cells –Rods Produce colorless vision Allow us to see in dim light

Inner Tunic Cones –Three different sets of cones –Allow for increased visual activity –Cones make up the fovea centralis Eryred/ Chloro-green/ cyan-blue (primary colors) White Light –Occurs in cones All three colors are mixed Black Light –Absence of color- of no light pigmnets in the cones are stimulated

Inner Tunic ROY G BIV –Visible light spectrum –Red- longest –Violet- shortest Posterior Cavity –Largest area of the eye –Contains the vitreous humor –Floaters that cast shadows on the visual receptors are usually located w/ in the vitreous humor Vitreous humor –Fills the posterior cavity –Supports the internal parts of the eye and ehlps to maintain its shape

Light Passage and Reception Cornea Aqueous humor Lens Vitreous humor Retina Fovea centralis Optic nerve brain

Light Passage and Reception Focusing –Refraction of light waves –Lens is concave Waves open out –Lens is convex Waves converge –Radial muscles of the iris contract Diameter of pupil decreases –Humors Help to refract light and provide shape

Visual Accessory Organs Lacrimal Gland –Tear gland –Tears contain enzymes that function to reduce the chances of developing eye infections Conjunctiva –Lines inner surface of the eyelids and covers the anterior surface of the eye