Physiology II: Vision I

Protective mechanisms of the eye: … (4)

bony socket, eyelids, tears, eye lashes

…: protects the eye except the anterior part

bony socket

…: close to protect anterior part of the eye → corneal blink reflex

eyelids

…: lubricating, cleansing, bacterial fluid (produced by lacrimal gland)

tears

…: capture and trap fine debris

eye lashes

…: patterns f light and dark hit the environment and objects around you

luminance

Signals that leave the retina as nerve impulses through the optic nerve, pass through the optic chiasm where they cross ans reach the … of the thalamus

lateral geniculate nucleus

The lateral geniculate nucleus organizes and … the signal, sends it to the primary visual cortex in the occipital lobe

sharpens

…: contains the aqueous humor

anterior cavity

Anterior cavity is divided into: … (2)

anterior chamber, posterior chamber

…: between cornea and iris

anterior chamber

…: between iris and lens

Posterior chamber

…: provides nurient and removes waste for cornea and lens (which have no blood supply, maintains intraocular pressure

anterior cavity

…: contains vitreous humor (gel-like, transparent), maintains the spherical shape of the eyeball, holds the retina in place against the choroid, allows light to pass tot he retina

Posterior chamber

…: white, tough outer fibrous layer of the eye, provides protection, maintains eyeball shape, provides attachment points for eye muscles

sclera

…: transparent front part of the sclera, allows light to enter, major role in refraction of light to help focus an image

cornea

…: middle, vascular layer of the eye (between the sclera and retina)

choroid

…: rich in blood vessels nourishing the retina

posterior choroid

…: becomes the ciliary body and iris

anterior choroid

…: thickened ring of tissue surrounding the lens, produces aqueous humor, contains ciliary muscle

ciliary body

…: adjusts lens shape for accommodation

ciliary muscles

…: colored part of the eye, with central opening called the pupil, controls pupol diameter to regulate how much light enters the eye

Iris

…: transparent, flexible, biconvex structure behind the pupil, refracts light to focus it on the retina, changes shape during accommodation for near and far vision

lens

…: inner sensory layer lining the back of the eye, contains photoreceptors that detect light, processes visual information an sends it via the optic nerve to the brain

retina

…: forms the aqueous humor

capillary network in aqueous humor

Aqueous humor is produced in the …, it flows through the … into the anterior chamber, drains out at the …

posterior chamber, pupil, iridocorneal angle

Drainage of the aqueous humor: the … filters the aqueous humor, … collects the aqueous humor, … drains into the venous blood system

trabecular meshwork, canal Schlemm, aqueous veins

…: if aqueous humor nor drained as rapidly as it forms → accumulation in the anterior cavity → raised intraocular pressure → causing retinal and optic nerve damage

glaucoma

…: round opening in the center of the iris through which light enters

pupil

… is important diagnostically (CNS pathologies and drugs)

pupil size

… → converge light

convex surfaces

… enter the eye almost parallel and requires less bending (refraction) to focus on the retina

distant light rays

… diverge more, they require more refraction to be brought into focus on the same point

near light rays

…: provides most of the eyes refractive power, fixed curvature, cannot adjust for focusing

cornea

…: the process of adjusting the lens shape to focus on near objects

accommodation

Accommodation is controlled by: … (3)

ciliary muscles, zonular fibers, lens

Lens shape

Distant focus: …

Near focus: …

flat, round

Innervation

Distant focus: …

Near focus: …

sympathetic, parasympathetic

Suspensory ligaments

Distant focus: …

Near focus: …

taut, slack

Ciliary muscle

Distant focus: …

Near focus: …

relaxed, contract

…: age 40, loss of elasticity of lens, cannot assume spherical shape required to accomodate for near vision → reduction in accommodation ability, corrective lenses for near vision

presbyopia

…: elastic fibers in the lens degenerate ane become opaque

cataracts

…: no refractive error

emmetropia

…: near sightedness, eyeball too long or lens too strong

myopia

Myopia

Far light source: …

Near light source: …

no accommodation blurry, no accommodation

Myopia with concave glasses

Far light source: …

Near light source: …

no accommodation, accommodation

…: farsightedness, long-sightedness, eye ball too short or lens too weak

Hyperopia

Hyperopia

Far light source: …

Near light source: …

accommodation, accommodation blurry

Hyperopia with concave glasses

Far light source: …

Near light source: …

no accommodation, accommodation

…: uneven curvature of the cornea in various planes

astigmatism

Astigmatism can ve corrected with …

cylindrical lens

Visible light is from … (violet) to …

400 nm, 700 nm (red)

Sensitivity to light peaks arounf …(green light), drops at the blue and red ends

500-550 nm

…: distance between two peaks or trophs

wavelength

Wavelength determines the … of light

color

…: height of the wave from midline

amplitude

Intensity determines the … of the light

brightness

The direction light travels is … to the direction of retinal visual processing

opposite

step 1: light enters the through the cornea and lens and passes through the …

front layers of the retina

step 2: in the … (at the back of the retina), light energy is converted into electrical signals

photoreceptor layer

step 3: Signals from the photoreceptor layer are passes to … (2), process and refine the visual signal before sending it to the brain

bipolar cells, horizonal and amacrine cells

…: connect photoreceptors to ganglion cells

bipolar cells

…: help with lateral interactions like contrast and edge detection

horizontal and amacrine cells

Step 4: … recieve the final processed signals and send acion potentials down their axons which bundle together to form the optic nerve

ganglion cells

Ganglion cells are the only retinal cells that fire … they are the “output cells”

action potentials

…: photoreceptors exposed directly to light (other layers pulled aside), highest concentration of cones, active sensing

fovea

…: optic disc, where the optic nerve exits the eye

blind spot

…: area of the central vision surrounding the fovea (sharpedt vision)

Macula lutea

…: leading cause of blindness, causes donut vision, age related

macular degeneration