Visual System, Diseases, and Impacts Flashcards
Oculomotor System
Made up of many brain areas that cooperate to stabilize images of interest on the high-acuity part of the retina
Sclera
Tough white outer layer of the eyeball
Provides protection and form
Cornea
Avascular clear front portion of the outer layer
Lets light rays enter the eyes and converges the light rays
Iris
Colored part of the eye
Behind cornea and in front of lens
Controls the amount of light entering the eyes
Ciliary Body
Portion of the uveal tract between choroid and iris
Ciliary muscle alters the power of the lens
Choroid
Layer between sclera and retina
Supplies blood to the retina
Retina
Inner sensory nerve layer next to the choroid that lines the posterior two thirds of the eye
Reacts to light and transmits impulses to the brain
Lens
Transparent biconvex structure behind the pupil
Helps bring light rays to focus on the retina
Optic Nerve
Cranial nerve extending from the optic disk to the optic chiasm
Carries electrical impulses from the retina to the optic chiasm in the brain
Vitreous Cavity
Space between the retina and optic nerve posteriorly and between the lens and the ciliary body anteriorly
Hold vitreous that helps maintain the shape of the eye
Macula
Functional center of the retina
Gives us the ability to see 20/20 and best color vision
Fovea
Responsible for central vision
Located at the center of the retina
Uveal Tract
Layer of tissue that runs between the cornea and sclera on the outside and the retina on the inside of the eye.
Made up of Irish, Choroid, and Ciliary Body
Optic Chiasm
Junction where fibers coming from the nasal portion of the retina of each eye split off from their optic nerves and cross over to the opposite side to join with fibers coming from the temporal portion of each retina from the opposite side
Optic Pathway to the brain
includes the retina, optic nerve, optic chiasm, optic radiations, and occipital cortex
Amblyopia
Reduction in visual acuity because of nonuse of that eye or marked differences in refractive errors of the two eyes.
Central vision loss
Nystagmus
Involuntary, rhymical. repeated movement of one or both eyes in a horizontal, vertical, or circular pattern.
Low visual acuity is caused by inability to maintain steady fixation of the gaze, most people perceive objects as being stationary
Causes central vision loss
Myopia
Means near sighted. There is a convergence insufficiency
Caused by an increase in eye length
Hyperopia
Farsighted
Eyes are shorter then the average length
Light rays converge behind the retina
Keratoconus
Extreme corneal curvature defect that results in the cornea becoming increasingly cone shaped
Central vision loss
Presbyopia
Lens becomes less flexible and less able than previously to accommodate for near point viewing. “arms aren’t long enough”
Presbyopia is a natural part of aging process and usually begins around age 40.
Cataracts
Formed when the lens of the eye becomes opaque.
Cataracts are a normal part of the aging process
Diabetic Retinopathy
When vitreous starts to pull away from the retina and vessels hemorrhage
Can effect both central and peripheral visual acuity
Macular Degeneration
Can be wet or dry; dry is more common
Dry is when a greater number of cone cells die
Can cause visual hallucinations and is a central vision loss
Central Scotomas
Areas of diminished or absent vision that result in a “blind spot” in the center of the visual field.
Affect acuity and color vision
Glaucoma
Condition in which intraocular pressure becomes sufficiently high to damage the nerves of the retina and optic nerve
Causes peripheral field loss
Retinitis Pigmentosa
Group of diseases that result in degeneration of the retina.
Causes peripheral loss
Homonymous Hemianopsia
Also called half vision. Results when a specific portion of the optic pathway malfunctions.
Loss of half the central field and entire peripheral field in the opposite eye. Only see one side in each eye.
Left brain injury = loss in right half of vision
Cortical Vision Loss
Result of damage to one or both occipital lobes
CVA
Cerebrovascular accident, also known as a stoke
CVA is most likely to cause Homonymous Hemianopsia
Normal lens changes with age
Lens hardens and become less flixible
Lens thickens
Lens becomes more yellow and absorbs more light
Normal pupil changes with age
Pupil size decreases
Normal changes light/dark adaptation with age
More sensitive to light
Harder time adapting to dark environments
Harder time adapting from dark to light or vice versa
