Chapter 14 Flashcards
How does the eye act like a camera?
- Lens of eye adjusts to bring object into focus
- Pupil of eye constricts to allow less light to enter in bright setting or dilates to allow more light to enter in darker setting
- Through bending of light rays, image reaches retina
- Sensitive nerve cell layer of eye
- Image is transmitted to brain for interpretation
What is the sclera?
- White portion of eye
- Tough, fibrous membrane
- Maintains shape of eyeball
- Serves as protective covering for eye
What is the iris?
The colored portion of the eye
What is the pupil?
- an opening in the center of the iris
- controls the amount of light entering the eye
- its diameter is regulated by relaxation and contraction of the iris
What is the conjunctiva?
- a thin mucous membrane layer that lines the anterior part of the eye (is exposed to air and inner part of eyelids)
- it is colorless but appears withe because it covers the sclera
- will look bloodshot if blood vessels become dilated due to irritation
Lacrimal gland?
- located at the upper out edge of each eye
- produces tears
What is the purpose of tears? What do they contain?
- they flow constantly across the conjunctival surfaces to cleanse and lubricate them
- help prevent bacterial infections
- contain lysozyme, an antibacterial enzyme
lacrimal duct
- located at the canthus (inner edge) of the eye
- the spot from which tears drain
eyelids
-continuous with the skin and cover the eyeball, keeping the surface of the eyeball lubricated and protected from dust and debris through blinking
eyelashes
- located along the edges of the eyelids
- further protect the eyeballs by preventing foreign materials and/or insects from getting to the eyeball
what is the uvea?
the vascular middle layer of the eye
-contains the choroid
what is the choroid?
-a layer just beneath the sclera which contains extensive capillaries that provide the blood supply and nutrients to the eye; the iris; and the ciliary body
the lens
-colorless biconvex structure that aids in focusing the images clearly on the sensitive nerve cell layer called the retina
ciliary body
- on each side of the lens
- secretes aqueous humor
- contains muscles responsible for adjusting the lens to view near objects.
suspensory ligaments
- radiate from the ciliary body
- straight fibrils that attach to the lens and hold it in place
- they respond to the contraction and relaxation of the ciliary body muscles to adjust the shape of the lens for proper focusing of the eye
accommodation
- the ability of the lens to focus clearly on objects at various distances
- the thickening and thinning of the lens causes the light rays to bend appropriately so the image will focus clearly on the sensitive nerve cell layer of the eye
- the lens accommodates for the closeness of an object by increasing its curvature to bend the rays more sharply so they will focus on the retina, producing a clear image
retina
- the third innermost layer of the eye
- changes the energy of the light rays into nerve impulses
how are the nerve impulses transmitted?
-via the optic nerve to the brain for interpretation of the image
rods?
cones?
- outer edges of the retina; responsible for vision in dim light and for peripheral vision
- responsible for visualizing colors, central vision, and vision in bright light
fovea centralis
- a small depression within the macula lutea
- where the highest concentration of cones exists
macula lutea
oval, yellowish spot near the center of the retina
central vision
when the image focuses directly on the fovea centralis and the sharpest image is obtained.
optic nerve
-where images from the retina are transmitted to the brain and interpreted as vision
optic disc
- insensitive to light
- no rods or cones
- known as the blind spot
- the center serves as point of entry for the artery that supplies the retina
what are the two cavities of the inner eye?
anterior chamber: in front of the lens and iris and behind the cornea
posterior chamber: between the iris and the suspensory ligaments
-both are filled with aqueous humor that flows freely between them
-the balance of production and absorption of the aqueous humor maintains proper eye pressure
vitreous humor
clear jellylike substance that gives shape to the eyeball
- is not constantly reproduced
- if a puncture occurs and it escapes, it can cause blindness
What is the process of vision
- light ray enters the eye
- light goes through the cornea, aqueous humor, pupil, lens, and vitreous humor to the retina
- once in the retina, sensitive nerve cells transmit the image through the optic nerve to the brain
refraction
the bending of light rays as they pass through the various structures of the eye to produce a clear image on the retina
The four errors of refraction
astigmatism
hyperopia
myopia
presbyopia
biomicroscopy
- ophthalmic examination of the eye by use of a slit lamp and a magnifying lens
- also known as slit-lamp exam