The Eye Ch 50 Flashcards
Optics of vision
Light travel speed air vs solids/liquids
Light travels rapidly through air and much slower through solds and liquids
Refractive index
specific to various media
rays bend if refractive index of new media is different
Refraction
angulated interface - rays bend if refractive index of new media is different
The direction in which light travels is _____ to the plane of the wave front
perpendicular
Convex lends causes
convergence of light
Focal point
All rays pass through this single point
Most clear, distinct image
Concave lens
Rays diverge (no focal point of rays)
Focal length
distance beyond convex lens where convergence takes place
Image formation: how many points of light source?
2
Image formation (3 steps)
- Light rays come to a point of focus on opposite side of lens
- Image is upside-down- lateral sides are reversed
- Brain flips image
4 refractive surfaces of eye
- Air and anterior surface of cornea
- Posterior cornea and aqueous humor
- Aqueous humor and anterior surface of lens
- Posterior surface of lens and vitreous humor
Refractive power of a lens is measured in
diopters
Accomodation
internal lens changes shape to provide
Lens role
focus image on retina (inverted and reversed)
What is responsible for lens accomodation
CN III, nerve nucleus
Presbyopia
lens grow larger, thicker and less elastic as we age (cant accommodate as well)
What physically causes/allows accommodation?
- Suspensory ligaments pull out = lens remains flat
- Ciliary muscles contract to release ligament tension = lens more spherical
Emmetropia
Normal, light rays are in sharp focus on retina
Hyperopia
Farsightedness: short eyeball, light rays are not bent enough my the time light hits retina (focal point is behind retina)
Myopia
Nearsightedness: eye ball too long, light rays focused in front of retina
Hyperopia fix:
Convex lenses
Myopia fix:
concave lenses
Small pupillary apeture
greater depth of focus
Large pupillary apeture
Blur circles
Astigmatism
Refractive error of the eye due to curvature of the cornea in one plane
accommodation is not able to compensate
Contact lenses work by
nullifying refraction of anterior surface of cornea
Cataracts MOA and correction
Proteins of lens fibers become denatured and coagulate
correction: surgical removal of lens, plastic lens implanted
Visual acuity is
Resolution
distinguishes 1 vs 2 things
Highest area in eye of visual acuity is ____
Fovea aka Macula lutea (in center of retina)
Why is fovea/macula lutea the area of highest visual acuity?
High concentration of cones
Binocular vision allows for
Depth
Depth involves (2)
- Size of images of known objects
- moving parallax, stereopsis
Role of intraocular fluid
maintains pressure to keep eyeball distended
Aqueos humor location
front of lens
Aqueous humor flows through
pupil into anterior chamber
Vitreous humor location
behind lens - gelatinous mass
Vitreous humor flow
no flow - fluids can diffuse
Normal intraocular pressure
15 mmHg
Intracocular pressure is maintained by
aqueous humor flow
Glaucoma
intraocular pressure becomes too high, can lead to blindness
Glaucoma MOA
Resistance to fluid outflow d/t acute inflammation or dissue debris