Vision Flashcards
Ability to BEND light
Refractive Power
measured in DIOPTERS
FIXED refractive power
CORNEA
VARIABLE refractive power
LENS
Focus FAR objects
ciliary muscle: RELAXED
suspensory ligaments: TENSED/TAUT
lens: FLAT
Focus NEAR objects (accommodation)
PARAsympathetic
CN III
ciliary muscle: CONTRACTED
suspensory ligaments: RELAXED (decreased tension)
lens: SPHERICAL
“Long Eyeball”: light rays converge IN FRONT of the retina
MYOPIA (nearsightedness)
BICONCAVE
“Short Eyeball”: light rays converge BEHIND the retina
HYPEROPIA (farsightedness)
CONVEX LENS
IRREGULAR/NON UNIFORM CURVATURE OF THE CORNEA: multiple convergences of light in the retina
ASTIGMATISM
CYLINDRICAL LENS
Age related loss of accommodation (>40 y/o)
Presents d.t. inability to contract (ciliary body)
PRESBYOPIA
CONVEX LENS (if initially with 20/20 vision)
Absorb stray light (PREVENTS LIGHT SCATTERING)
Converts 11-cis retinal to all trans retinal
Involved in MACULAR DEGENERATION, RETINAL DETACHMENT and ALBINISM
Pigment Epithelial cells
SENSITIVE to LOW INTENSITY LIGHT (NIGHT VISION)
high concentration in PARAFOVEAL region
RODS
SENSITIVE to HIGH INTENSITY LIGHT (DAY,COLOR VISION)
present in FOVEA CENTRALIS (area of most acute vision)
CONES
INTERNEURON b/w receptor cells (rods, cones) and ganglion cells
CONTRAST DETECTORS
Bipolar cells
Interneurons
Form local circuits w/ bipolar cells
Amacrine, Horizontal cells
Maintains INTERNAL GEOMETRY of the retina
Muller cells