ABO Study Guide
Eyelids - answerprotect the eye from foreign bodies and excessive light
average blink rate is 7 to 12 times per minutes
lids spread tears over the corneal surface to create a smooth surface
they also wash away dirt and debris, protects against diseases
palpernral fissure - answ...
Eyelids - answer✔✔protect the eye from foreign bodies and excessive light
average blink rate is 7 to 12 times per minutes
lids spread tears over the corneal surface to create a smooth surface
they also wash away dirt and debris, protects against diseases
palpernral fissure - answer✔✔averages 15mm high by 30mm wide
extra-ocular muscles - answer✔✔medial rectus- towards the nose
lateral rectus- away from the nose
superior rectus- upward
inferior rectus- downward
superior oblique- top of the eye toward the nose
inferior oblique-top of the eye away from the nose
cornea - answer✔✔clear outer portion of the eye
light rays pass through the cornea
transparent with no blood supply of its own, tears supply the nutrients
refractive power of 60D cornea provides 2/3 refractive power crystalline lens provides 1/3
average horizontal diameter of 11.7mm
vertical diameter of 10.6 mm
Iris - answer✔✔the colored part of the eye
controls the light inside the eye
color come from melanin
can allow more light when its dim
VID visible iris diameter HVID horizontal visible iris diameter
crystalline lens
responsible for 1/3 of the eyes refractive power (average 15D to 16D)
transparent and has no blood supply
bi-convex, focuses light rays onto the retina
Ciliary Muscles - answer✔✔zonular fibers connect the ciliary muscles to the crystalline lens
muscles change the shape of the crystalline lens
when it contracts the zonulars relax it allows the lens to thicken increasing the eyes ability to
focus up close
the ability of the eye to change focus is called accommodation
presbyopia - answer✔✔the loss of accommodation is called presbyopia (need near and distance
vision)
cataracts - answer✔✔cloudy opacities in the crystalline lens
when a patient has had a cataract removed they can be aphakic (without a crystalline lens) or
pseudophakic (with an IOL or intraocular implant)
retina - answer✔✔captures light rays and converts them into electrical impules
contains 125 million rods that are responsible for night vision
6 to 7 million cones responsible for color and light vision
the macula - answer✔✔is found at the center of the retina and allows us to see fine details
the fovea - answer✔✔only contains cones and is responsible for the sharpest vision
macular degeneration - answer✔✔results in vision loss in straight ahead gaze
optic nerve - answer✔✔the optic nerve carries images from the retina to the brain
the optic nerve creates a blind spot
a healthy optic nerve is necessary for healthy vision
Spectacle RX (OD, OS, OU) - answer✔✔OD- oculus dexter, OS- oculus sinister, OU- oculus
uterque
minus means myopia,plus means hyperpobia, plano indicates no rx
quarter steps are common, but they can be broken down into eighths
OD's put a minus cylinder and MD's put a plus cylinder
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