Lecture 02 - Vision 1 Flashcards Preview

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Flashcards in Lecture 02 - Vision 1 Deck (25):

Cornea and sclera

cornea = super organized, distinct planes = clear
sclera = disorganized, randomly oriented= opaque
-though, thick, inelastic collagen, outer wall of eye


Anterior chamber (aqueous humour)

between cornea and iris
-clear, watery aqueous humor
-measure this for dilation



vascular muscular diaphragm
-pupil: central opening
-diameter of pupil under neural control (PS, Symp)



proteins (collagen) assembled to be optically clear and flexible
-lens epithelial cells organized front to back organization because size limited


Ciliary body

-connects lens to scleral wall
-muscle and secretory epithelium
-neural control of ciliary muscle affects shape of lens, independent of iris/pupil
-lens capsule is under constant pull from ciliary muscle
-relax muscle, lens naturally curl up and change shape --> accomodation


Vitreous Chamber/cavity

optically empty gel of hyaluronic acid molecules
-physically supports retina layer to remain in place against scleral wall


Retina and Choroid

Neural and vascular layers lining inside of scleral wall
-minimize blood structures blocking vision


Optic Nerve

collection of retinal nerve cell axons transmitting info to Lateral Geniculate Body via optive nerve --> optic chiasm --> optic tract --> lateral geniculate body
-outer sheath is contiguous with CNS dura mater
-get myeline so light passage isn't disturbed
-ganglion cell bodies in retina, axons travel to common exit area and gather into cylinder


Hyaloid Canal

Remnant of embryology
-eye starts as tube and develops into sphere
-canal is not visible clinically
(potential structure, not anatomic)


Principles of Refraction

At interface of two materials of different optical densities, light bends towards the perpendicular of the surface of the interface
-affect bending by changing curvature of the interface or changing optical densities

***surface of cornea is more important for light focusing because of the curvature than lens
-largest refraction at air:tear interface


Function of the lens

refraction/focusing of image by accomodation
-change lens shape to focus on distant or near images (changing focal distance)
-relaxing ciliary muscle --> lens become more round



lens capsule is elastic
-totally relaxed state of lens = round
-ciliary muscle contracts to allow the lens to be more round
- Parasymp:
edinger-westphal --> CN3 --> ciliary ganglion (in eye socket) ***synapse --> ciliary nerve --> ciliary muscle


Pulillary Aperture

pupil size important variable in vision
-adapt to amount of ambient light
-smaller pupil = increased depth field = "pinhole effect"
-pinhole minimizes blur of other light rays coming in
-distinguishes between lens refraction angle issues from other issues like optic nerve/retina problems


Structure of Pupil

-pupil margin = circular muscle (sphincter pupillae)
-parasymp control (ACh, pilocarpine
-edinger-westphal --> CN3 --> ciliary ganglion --> ciliary nerve --> sphincter

-within stroma of pupil = radial muscle (dilator pupillae)
-symp control (epinephrine, congeners)
-pharmacologically parasymp antagonists = dilation (drops for dilation)
-lateral horn --> superior cervical ganglion --> ciliary nerve --> dilator


Retinal cell types

4 types of cells
1. Retinal pigment epithelium - support photoreceptors, absorb light and heat (lots of blood, garbage trucks for 2)
2. Rods and cones - change light energy to synaptic energy (physical to chemical)
3. Interneurons - relay, process, modify image signals WITHIN RETINA
4. Ganglion cells - relay, process, modify image signals TO BRAIN (brain can't interpret if these are lesioned)



convert photons into neural information


interneurons & ganglion cells

process and transmit neural info


retinal pigment epithelium

support metabolic needs of photoreceptors
heat sink
absorb unprocessed photons



Rods are sensitive (function even in low light)
"white" only - no color perception
great numbers in retinal periphery (image locator)
none in center
wide connections to interneurons - 1000 rods to 1 ganglion
allows sensitivity



insensitive: require much ambient light
color vision (RBG)
greater number in central retina (macula) to give detail and locater analyze function (image resolution)
none in peripheral retina
very narrow connections to interneurons (often 1:1)
allows detail
cell bodies form foveal pit
different cones combine to get different colors


Foveal Pit

Mostly cones - RBG analyzer
-age related macular degeneration = color degen
-forms dark circle in the eye because absorbing color, not bouncing light off on the way
-curved fibers


Central visual pathways

visual fields
retinal projections
visual cortex


Visual fields

receptive areas of retinal cells
-geographically organized --> lateral geniculate body
-split from Right/Left eye into Right/Left fields of vision
-right field, left field overlap = true binocular vision
-right fields and left fields become joined/overlaid at optic chiasm


Retinal projections

lateral geniculate = synapse
segregation/retinotopy - right/left and upper/lower


Visual cortex

From lateral geniculate body to cortex - optic radiations