17 Vision 1 Flashcards
The cornea of the eye is contiguous with which structure that provides a tough, normally inelastic collagen covering on the eye?
the sclera
Where is the anterior chamber and what does it contain?
between cornea and iris, contains a clear watery aqueous humor (this fluid is recycled throughout lifetime)
As adults age, what happens to the shape of the lens?
becomes more spherical and less disc-shapped which results in more difficulties with accommodation (reading glasses)
What are the functions of the ciliary body?
connects lens to scleral wall, contains muscle and secretory epithelium which manufacture aqueous humor and under neural control it affects the shape of the lens
What is the most important function of the vitreous chamber?
the optically empty gel of hyaluronic acid molecules which supports retina layer against the scleral wall
What are the names of the neural and vascular layers that line the inside of scleral wall.
retina (neural) and choroid (vascular)
Collection of retinal nerve cells actions transmit info to the ____ ____ ____ by way of the optic nerve, optic chasm and optic tract. (sheath continuous with the CNS dura mater.
LGB- lateral geniculate body
Light traveling toward the retina is refracted the most between what two layers (these layers have the greatest difference in refraction index)
between the air and the tear film (the tear film/ air interface causes the greatest refraction)
If the tear film interface creates the most refraction, what is the purpose of the lens in creating an image on the retina?
lens has the ability to accommodate to focus on far or near objects
How do ciliary muscles cause accommodation of lens?
ciliary muscle contractions means contraction of the sphincter muscle which creates less outward pull on the lens, allowing it to round (allows near objects to be focused) NOTE: the difference in shape during accommodation is very small
What types of nerves control accommodation?
parasympathetic fibers in the following pathway: Edinger-Westphal nucleus, CN III, ciliary ganglion (synapse), ciliary nerve, ciliary muscle
What are emmetropia, hyperopia and myopia respectively?
emmetropia (focusing power matches eye) hyperopia (farsightedness) and myopia (nearsightedness) **length of eye is too long
What muscle and general nervous system is responsible for pupil constriction?
sphincter papillae (circular muscle): under parasympathetic control (EW to CNII etc)
What muscle and general nervous system is responsible for pupil dilation
dilator pupillae (radial muscle) under sympathetic control (via lateral horn of cervical ganglion to ciliary nerve)
What general types of pharmacological agents are used in combination for eye dilation?
encourage dilation with sympathetic agonist (ie. epinephrine) and parasympathetic antagonists (ie. atropine, tropic amide)
What are the 4 types of retinal cell types to know?
retinal pigment epithelium, rods/cones, interneurons, and ganglion cells
What is the purpose of pigment epithelium?
support photoreceptors, absorb light and heat (analogy of burning ants)
What are the function of rods and cones?
change light energy to synaptic energy
What is the role of interneurons in the retina?
the relay, process, modify image signals within the retina (begin processing of images still within retina)
Why is the retina structure considered “inverted”
photoreceptors are deep to the nerve ganglia on the surface of the retina, photoreceptors also have metabolic needs that are addressed by their close contact with the base of the retina
What is the function of ganglion cells in the retina?
relay, process, modify images signals to the brain
Compare and contrast the functions of cones and rods
rods are very sensitive, found in in the periphery of the center, cones require a lot of ambient light but they convey color vision found centrally and in low ratio to interneurons/ganglia (1:1 often)
What does the tern retinotopic map mean?
signal messaging that conveys a “map” the visual input to the eye is preserve in the sense that signals travel relative to each other in the same pattern from the eye through the nerve
Why is the foveal pit in the shape of a depression?
the ganglion and bipolar cells are brushed aside from the center of the pit
