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
OUTPUT cell of the retina
Axons form OPTICC NERVE
GANGLION cells
P cells: color, form, fine details
M cells: illumination, movement
W cells: unknown function
Lesion in the optic nerve
Total loss of vision in the affected eye
Lesion in the optic chiasm (midline)
heteronymous bitemporal hemianopia
Lesion in the optic tract
contralateral homonymous hemianopia
Lesion in the temporal lobe (Meyers loop)
superior left homonymous quadrantonopia (pie in the sky)
Lesion in the parietal lobe (right)
inferior left homonymous quadrantonopia (pie in the floor disorder)
Homonymous hemianopia with macular sparing involve
CALCRINE FISSURE
Cutting which structure causes total blindness in the left eye
Optic nerve
Cutting which structure causes blindness in the temporal fields of the left and right eyes
Optic chiasm
Cutting which structure on the right side causes blindness in the temporal field of the left eye and the nasal field of the right eye
Optic tract
Area in the retina with no light sensitive rods or cones
No image detection
Where the ganglion cells axons exit the eye to form the optic nerve
Optic Dic (Blind spot)
3 cells types in the visual cortex that detect shape and orientation of figures
Simple cells
Complex cells
Hypercomplex
Have center surround and on-off patterns, elongated rods
Respond to BARS OF LIGHT with correct position and orientation
Simple cells
Respond to MOVING BARS or EDGES of LIGHT
Complex cells
Respond to LINES with PARTICULAR LENGTH and to CURVES/ANGLES
Hypercomplex
Have center surround and on-off patterns
Respond to BARS OF LIGHT with correct position and orientation
Simple Cells
Respond to MOVING BARS or EDGES OF LIGHT
Complex Cells
Respond to LINES with PARTICULAR LENGTH and to CURVES/ANGLES
Hypercomplex
Location of Blind Spot
12-15 degrees temporally
1.5 degrees below horizontal meridian
