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48 Cards in this Set
- Front
- Back
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What is the purpose of the parts of the eye?
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to bend and direct reflected light to the retina so that a strong visual stimuli can pass to the occipital lobe for interpretation.
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what is the purpose of the eyelids, eyebrows, eyelashes?
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keep dust and debris out
distribute tears over eye |
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which nerve controls blinking?
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CN VII - facial nerve
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which nerves control eye movement?
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CN III, IV, VI - cardinal fields of gaze.
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Purpose of conjunctiva -
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glands in conjunctiva secrete tears and mucus.
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Sclera -
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white, tough shell that protects the intraocular structures; contains blood vessels for nourishment.
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Cornea -
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avascular and transparent, allows light to enter the eye.
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How is the curvature of the cornea designed?
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to refract light so it focuses on the retina.
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how does the cornea get nutrients and oxygen?
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from tears and aqeous humor.
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what is the lacrimal apparatus?
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it produces the tears which provide oxygen and nutrients to cornea.
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Is the lacrimal apparatus bactericidal?
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yes, slightly
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why are older pts. more prone to eye infections and have trouble wearing contacts?
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tearing decreases with age.
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IRIS -
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produces the color and controls the pupil.
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Pupil -
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dilates and constricts to control the amount of light which enters.
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what causes the pupil to constrict?
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CN III and parasympathetic stimulation.
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What causes the pupil to dilate?
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CN V and sympathetic stimulation.
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Crystalline lens -
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avascular and transparent structure behind the iris.
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function of crystalline lens
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bends light so that is strikes the retina appropriately.
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what controls the shape of the lens (thus the focal point)
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the ciliary body.
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Ciliary Body -
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include the muscles which attach to the lens and change the shpae of the lens by contracting and relaxing and the ciliary processes which produce the aqueous humor.
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Canal of schlemm
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opening which allows the aqueous humor to leave the anterior chamber.
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choroid -
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the very vascular structure that provides nourishment to the ciliary body, iris, and outer part of the retina.
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retina -
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the extension of the optic nerve.
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does the retina regenerate?
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no
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how does the retina affect images?
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it converts them to a form that can be interpreted by the brain.
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what are the two types of photoreceptor cells?
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rods and cones.
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what are cones responsible for?
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daylight vision, high resolution vision, and color
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where are cones located?
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concentrated in fovea: red and green are in fovea, blue are outside fovea and are fewer in number so that blues are less intense.
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DO cones adapt to change in light level?
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yes, rapidly
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what are rods responsible for?
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night vision (very sensitive to light) but adapt slowly.
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How long does it take for full night adaptation?
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30 minutes
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rods have better motion ...
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sensors
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where are rods located?
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none in fovea, but dominant in periphery so that motion is detected quickly in periphery.
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what color do rods not see?
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red, so that use of a red light does not interfere with dark adaptation.
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fovea centralis -
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center of retina
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does it have rods and cones?
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cones only; has the sharpest visual acuity.
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macula -
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area surrounding fovea centralis;
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rods or cones?
avascular or vascular? |
large number of cones
very few blood vessels |
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optic disk -
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area where the optic nerve, retinal arterioles and veins enter and leave the spot; blind spot.
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anterior compartment -
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it is the aqueous humor which is clear, watery fluid.
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how is the watery fluid produced?
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by the ciliary process, passes through the pupil from the posterior chamber to the anterior chamber into the canal of schlemm where it is diffused into the scleral veins and then returned to the general circulation of the body.
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what is the purpose of the fluid?
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nourish the lens and endothelium of the cornea.
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How does it affect intraocular pressure?
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by increased production or decreased outflow.
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what is normal IO pressure?
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10-21 mmHg.
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what is necessary for the lens and aqueous humor to transmit light rays?
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must be absolutely clear.
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posterior compartment
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the vitreous humor = gel
may contain normal cellular debris (floaters) or blood from injured eye. |
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how does age affect the vitreous humor?
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it becomes more liquid
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is the vitreous humor readily replaced?
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no
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