Vision

fibrous layer

outside layer of eye ball

contains cornea + sclera

vascular/choroid layer

middle layer of eye ball

contains blood vessels, melanin, iris, pupil, ciliary muscles

sensory/neural layer

inside layer of eye ball

contains retina, rods, cones

vascular layer (choroid, iris, pupil, melanin, muscles)

what part of the eye contains blood vessels?

would block vision, made of tissue that doesn’t contain/need blood supply?

Why are there not blood vessels in the cornea or lens?

sphincter pupillae muscle, bright light, distance of focus cause lens to change shape

What factors into pupil dilation/constriction?

Photopupillary reflex

pupils constrict because of bright light

ciliary muscles relax, lens is elongated (tall + thin) and flattened (dilation)

Fight or flight effect on vision: set up for distant vision

ciliary muscles contract (lens is short and thick), pupil constriction, convergence (medial rotation)

Rest and digest effect on vision: set up for close vision

crystalline protein

what the lens is made of

very tough but crystalline proteins and ciliary muscles allows it to be elongated or shorted

how is the lens “flexed?”

cataracts

clouding of lens; oxidation of crystallin proteins--blocks light from coming through

caused by age, diabetes, smoking, intense light, ionizing radiation

aqueous: watery, anterior chamber

vitreous: thick, posterior chamber

(divide at lens)

aqueous humor vs vitreous humor?

most numerous photoreceptor

Dim light

More sensitive to light- peripheral and night vision (more rods at edges)

NOT color- gray scale

NOT sharp images- many rods on one optic nerve

tell me everything know know about rods

MANY rods connect to one optic nerve

Why do rods produce fuzzy images?

poor sensitivity- require bright light

faster reaction

COLOR- red green blue

crisp images- each cone/option nerve

every person perceived different shades

tell me everything you know about cones

retina of neural layer

where are rods and cones?

photoreceptors

light absorbing cells; special sensory receptors

rods and cones

color blindness

lack of one or more cone pigments (red, green, or blue)

most common: red-green

hereditarily linked to the X-chromosome

why is color blindness more common in males?

absorbs light and colors the iris

purpose of melanin?

refraction

bending of light as light passes from one medium to another

1) into cornea (air→liquid)

2) into lens (aq humor→lens)

3) leaving lens (lens→vitreous humor)

In what locations does refraction occur in the eye?

cornea (air→liquid)

Where is the greatest amount of refraction?

lens + cornea direct light onto the fovea

How does our eye focus light onto the fovea?

improper refraction (everyone)

What causes an astigmatism?

upside down and backwards

How does the image formed on the retina differ from the image in front of us in reality?

wavelength

What aspect of light determines its color?

shorten front to back

How does the shape of the eyeball change with aging?

emmetropia

even normal eye focus

focal point is on retina

20/20 vision

myopia

nearsighted

eyeball too long

focal point is in front of retina

hyperopia/presbyopia

farsighted

eyeball too short

focal point behind retina

binocular vision

Each eye “sees” a slightly different view

Field of view overlaps for each eye

depth perception/3-d vision

what does binocular vision allow for?

glaucoma

too much aqueous humor

chalazion

infected tarsal gland with cyst formation

big and rare

sty

inflamed/infected sebaceous gland

conjunctivitis/pink eye

either viral or bacteria infection that inflames the conjunctiva (membranes around the eyelids and eyeball)

your lacrimal sack that contains your tears connects to the nasolacrimal duct which empties into the nasal cavity

why does your nose run when you cry?