Chapter 51 and 52- Understanding the Sensory System- Med Surgical- EYES External eye structures
Eyelids-protective cover for thr eyeball
* Has a thin transparent membrane called “conjunctiva” Eyelashes-keep dust out of eyes
Each eyelid has a lacrimal gland at the upper outter corner of the eyeball Question: how do tears come in front of the eyeball?
A: small ducts bring tears to the front and blinking help spread the tears over the surface
Q: what enzyme inhibits the growth of bacteria on the surface of the eyes? A: tears have enzymes called lysosome
How to collect tears?
Tears from Lacrimal canalsdrain into lacrimal sac nasolacrimal ductnasal cavities
Question: How do we do a nursing assessment of the eyes?
Answer: Inspect and palpate of the external eye
Internal Anatomy of the Eye
Choroid layer: Prevents glare
Ciliary Body: Circular Muscle changes the shape of lens
Circular Iris: Dilates, Constricts Pupil
Vitreous Humor: Holds Retina in Place
Aqueous Humor: Nourishes Lens/Cornea
Retina: Lines Posterior Eyeball
Contains Rods (Light) black and white
Cones (Color) for Vision
Fovea: Most Acute Color
VisionOptic Nerve: Transmit Image
* Retina: Lines Posterior Eyeball, Problem with
* Cones (Color) for Vision
* Usually can not see colors red, green, blue or a mix of these colors. * Mostly men
* Genetic predisposition
The retina is a light-sensitive layer at the back of the eye that covers about 65 percent of its interior surface. Photosensitive cells called rods and cones in the retina convert incident light energy into signals that are carried to the brain by the optic nerve. In the middle of the retina is a small dimple called the fovea or fovea centralis. It is the center of the eye's sharpest vision and the location of most color perception.
There are 6 intrinsic muscles that moves the eyeball are attached to the orbil and outter surface of the eyeball The cranial nerves that innervate these muscles are:
* Oculomotor 3rd
* Trochlear 4rth
EYEBALL has 3 layers
1. Outter fibrous tunic( sclera and cornea)
-sclera- white part of the eye/cornea- no capilliaries and 1st part refract light rays 2. Middle vascular tunic(choroid, ciliary body, and iris) * Choroid=has BV and dark pigment melanin(prevent glare)/anterior of chroid is mmodified into ciliary body and iris 3. Inner nervoous tunic (Retina)
* Lines 2/3of eyeball, has rods and cones, photoreceptors, fovea= only see color b/c only has cones. * Rods are more abundant toward periphery vision see best at night at side of visual field Nursing Assessment for Cranial Nerves of the eyes by eye movements:
Physiology of Vision:
* Involves Focusing of Light Rays on Retina and transmission of Subsequent Nerve Impulses to Visual Areas of Cerebral Cortex * Light rays strike the retina, it stimulates chemical RX in rods and cones. Retinal( a receptor) bonds to a protein called a opsin. In rods, the light rays stimulate the breakdown of rhodopsin into opsin and retinal resulting to chemical changes and generates a nerve impulse for transmission. Cones have a similar RX that takes place.
Nursing Assessment of the eye and visual status:
* Peripheral vision/by confrontation – how far you can follow the light while looking straight. decreases as age increases * Visual Fields-
* Full peripheral fields
* Movements in all 6 cardinal fields of gaze
* Corneal light reflex test ( light is at the same place in both pupils) * Cover test- steady gaze
** Also test with Snellen’s chart- read from smallest letter to biggest. 20/20- the vision is normal
20/70visual impairmentit takes the eye 70 ft to read what a...
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