THE EYE CHAPTER 10

QOD #1: Pre-Test 1.) 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 eye 70% 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 diameter 3 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 Light Cornea Aqueous humor Pupil Lens Vitreous humor Retina

EYE PHYSIOLOGY EYE PHYSIOLOGY Refraction: occurs when light waves are bent ◦ Normal ◦ Image is upside down ◦ Visual cortex of brain interprets it in its proper position

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 ACUITY Ophthalmoscope: 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 problems Myopia: near sighted Hyperopia: far sighted Emmetropia: normal vision Astigmatism: cornea/lens developed an irregular shape Strabismus: cross-eyed Diplopia: 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.. Cataract: lens becomes cloudy (laser surgery to fix) Glaucoma: increase in intraocular pressure, caused by an increase in aqueous humor Tonometer: 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 