THE EYETHE EYECHAPTER 10

QOD #1: Pre-TestQOD #1: Pre-Test1.) What are the 5 senses?2.) T/F Of all the sensory receptors in the

body, 70% are in the eyes.3.) T/F Your eyebrows have no function.4.) T/F If you are colorblind, you do not

see any color.5.) T/F If you are farsighted, you cannot

see objects that are in close proximity.6.) _________ is caused by an increase in

pressure in the eye.

The eyeThe eye70% of sensory receptors in the body are found

here.Housed in the orbit of skull and surrounded by

fat, blood vessels, nerves, and connective tissues.2.5cm in diameter3 layers (tunics/coats)

◦ Outer layer (fibrous) Protective, refracts light Includes cornea and sclera

◦ Middle layer (vascular) Contains pigments to keep eye dark inside Includes choroid coat, ciliary body, lens, iris, pupil, aqueous

humor.

◦ Inner layer (nervous/sensory) Visual receptors Contains retina, fovea, optic disc, vitreous humor

Pathway of LightPathway of Light

CorneaAqueous humorPupilLensVitreous humor Retina

EYE PHYSIOLOGYRefraction: occurs when light

waves are bent◦Normal◦Image is upside down◦Visual cortex of brain interprets it in its

proper position

Physiology cont…Physiology cont…Accomodation:

◦ Occurs when the lens adjusts its shape to focus on objects.

◦ Ciliary muscles and suspensory ligaments aid in doing this When the ligaments pull outward the lens

flattens and focuses on distant objects When ligaments are relaxed the lens is more convex (thickens) focusing on closer objects

VISUAL ACUITYVISUAL ACUITYOphthalmoscope: instrument

that illuminates the interior of eyeball allowing the inside to be seen.

Snellen eye chart: ◦ measure acuity◦ 20/20 normal vision◦Higher the number the poorer the vision

Eye problemsEye problemsMyopia: near sightedHyperopia: far sightedEmmetropia: normal visionAstigmatism: cornea/lens developed

an irregular shapeStrabismus: cross-eyedDiplopia: double vision (can be caused

by one eye deviating from line of vision).Blindness: most common cause is loss

of transparency of the cornea◦ Cornea transplant (high success rate b/c no

blood vessels)

Eye problems cont..Eye problems cont..Cataract: lens becomes cloudy (laser

surgery to fix)

Glaucoma: increase in intraocular pressure, caused by an increase in aqueous humorTonometer: instrument measuring pressure

Night blindness: poor vision in dim light resulting from a vitamin A deficiency.

Normal Vision

Color Blind

Color Blindness: Genetic disorder carried on the X chromosome. Most common is red/green color blindness.

Normal Vision

Color Blind