The eye Flashcards
List the major structures included in the eye.
- the eyeball
- optic nerve
- eyelids
- extra - ocular muscles
- components of lacrimal apparatus
Name the bones which form the orbit and the four major openings into/out of the orbit.
Bones:
- Frontal bone
- Sphenoid bone
- Ethmoid bone
- Palatine bone
- Maxilla
- Lacrimal bone
- Zygomatic bone
Four Major openings:
- Aditus Orbitalis (anterior opening)
- Optic Canal of the sphenoid bone (posterior aspect)
- transmits optic nerve - Superior Orbital fissure (posterior aspect)
- transmits CN 3,4,5 (ophthalmic) ,6 - Inferior Orbital fissure (posterior aspect)
- transmits part of maxillary branch of trigeminal nerve and infraorbital vessels
Know what bones of the orbit form the superior, lateral, inferior, and posterior wall.
Frontal bone = superior wall
Zygomatic bone = lateral wall
Maxilla = inferior wall
Sphenoid bone = posterior wall
Know what bones form the medial wall.
Lacrimal, palatine, and ethmoid.
Define the following ocular landmarks: anterior and posterior poles, axis of eye, equator of eyeball.
Anterior Pole: center of the eye’s anterior aspect
Posterior Pole: center of the eye’s posterior aspect
Axis of eye: imaginary line connecting the poles
Equator of eyeball: plane perpendicular to the axis halfway between the two poles
Name the three major layers of the eyeball, the major subparts of each, and schematically represent and label them in a drawing of a sagittally sectioned eyeball. (pg.406)
- Fibrous Tunic (Fibrous Coat)
- schlera (white of the eye)
- cornea - Vascular Tunic (Vascular Coat/ Uveal Tract)
- iris
- ciliary body (contains ciliary muscle which controls the thickening of the lens)
- choroid - Internal Tunic (Internal Coat)
- retina
- lens
- chambers
Demonstrate an understanding of the retina including the number of layers that compose it
10 layers in the Retina!!!
You only need to know:
- Internal limiting layer: deepest limiting layer of the retina and the one that incoming light strikes first (light goes from deep to superficial)
- External limiting layer: membrane- like layer formed by the outer parts of radial gliocytes
- Layer of Rods and Cones: the outer, light sensitive portions of the visual cells. Rods allow black and white vision and function in low level light. Cones allow color vision including black and white and function in bright light.
- Pigmented layer: contain pigment called fuscin. most superficial retinal layer and is last layer encountered by light.
What is the disc of optic nerve? What is the macula and fovea centralis?
Disc of optic nerve: blind spot; contains no rods or cones (devoid of visual cells)
Macula has a central portion called the fovea centralis. Fovea Centralis = provides best visual acuity because it is composed of almost entirely cone cells.
What is the lens?
The lens is what refracts lights and focuses inverted and reversed images onto the retina.
- the lens is somewhat elastic with a tendency to become thicker (due to ciliary muscle)
- decreased tension of the suspending zonular fibers allows the lens to assume a thicker anterior/ posterior profile
Compare rod and cones in regard to color sensitivity, visual acuity, and functionality at various light levels. Use this to explain why color vision does not occur in very dim light and why visual acuity is reduced at dusk.
Rods only work at low level lights and only allow black and white vision.
Cones require more light to function, give sharper visual images than rods, are responsible for all vision at medium and high light levels and all color vision.
This is why color vision doesn’t work in dim light because bright light is needed for cone cells to work.
Visual acuity is best in color vision which is why when dusk occurs our visual acuity decreases. There’s less light and less chance for our cones to give sharp visual images.
Discuss the production, flow, and reabsorption of aqueous humor and explains what happens in glaucoma.
Aqueous humor is continuously secreted by cells on posterior aspect of the iris.
It is reabsorbed from the anterior chamber by flowing back into the venous system through a number of opening termed schleral venous sinuses.
Glaucoma: is the interference with the reabsorption of aqueous humor causing increased intra- ocular pressure due to its continual production
IT CAN LEAD TO BLINDNESS IF NOT MEDICALLY OR SURGICALLY CORRECTED
Name the items that must be penetrated in order for incoming light to reach the rods and cones.
The first 8 layers of the retina!
Explain the process of accommodation
Accommodation: changes in lens thickness in order to properly focus images of nearby vs. distant objects on the retina
- to focus nearby images the lens needs to thicken :
1. the ciliary m. of the eye contracts causing a decrease in tension on the zonular fibers (decrease in diameter of ring formed by ciliary body) which allows the eye to “ball up” = thickens - to focus distant objects the ciliary m :
1. relaxes and the lens thins out and the diameter of the ring formed by the ciliary body increases
Relate accommodation to myopia and hyperopia (and their correction with artificial lenses.)
Myopia (nearsighted) - image is located anterior to retina
- lens is too thick and eyeball is abnormally elongated in an anterior/posterior direction
Concave (Diverging) lenses are needed
Hyperopia (farsighted) - image is located posterior to retina
- lens fails to thicken and eye ball is too short along its anterior/posterior diameter
Convex (Converging) lenses are needed
Show how the arrangement of smooth muscle fibers in the iris allow both dilation and constriction of pupillary diameter. Briefly discuss the influence of light level (bright/dim) on pupillary diameter.
pg. 415
In bright light the pupillary sphincter muscle is stimulated by parasympathetic neurons causing constriction of the pupil to reduce the amount of incoming light
In dim light the pupillary sphincter muscle contracts to allow more light into the eye. (it has radially arranged fibers that cause the pupil to enlarge)
