VIII-Vision/Disorders

Question 1

astigmatism

Answer 1

refractive error due to irregular curvature of cornea
-light rays unevenly bent so no single focus on retina
-can coexist with myopia, hyperopia, presbyopia

treat with cylindrical correction glasses

Question 2

hyperopia

Answer 2

far sighted
-light rays focus behind the retina

Question 3

myopia

Answer 3

nearsighted
light rays focus in front of retina

Question 4

cataract

Answer 4

cloudy/opaque area in ocular lens from aging, congenital, radiation, trauma, drugs, diabetes
-dec visual acuity/blurry vision, glares, dec color perception

treat with artificial lens replacement

Question 5

presbyopia

Answer 5

decreasing accomodation range with age bc lens loses elasticity
-near point recedes/gets further away so near vision tasks more difficult

Question 6

amblyopia

Answer 6

defective brain-eye interaction = reduction in vision that cannot be corrected by glasses

seen in developmental strabismus

Question 7

diplopia

Answer 7

double vision

Question 8

blind spot

Answer 8

where optic nerve leaves retina

Question 9

color blindness

Answer 9

genes encoding red and green pigments on X chromo so dysfunctional cone photoreceptors esp in men

Question 10

how to correct myopia

Answer 10

concave lens
-moves focus back onto retina

Question 11

how to correct hyperopia

Answer 11

convex lens
-moves focus forward so rays fall directly on retina

Question 12

accomodation process

Answer 12

to change focus from distant/near

1. contract ciliary muscle
2. reduce tension in zonule fibers
3. lens more elastic so inc curvature

Question 13

ionic mechanisms of phototransduction

Answer 13

IN DARK
1. cGMP keeps Na (ligand gated) channel open so constant depolarization and Glu release
WHEN LIGHT
2. visual pigment activated, rhodopson in rods (GPCR)
3. transducin activated to reduce cGMP via phosphodiesterase hydrolysis so Na channels close = hyperpolarize, dec Glu release

Question 14

functional difference rod/cone vision

Answer 14

rods constant activated in darkness

Question 15

vitamin deficiency in night blindness

Answer 15

vitamin A required to recyle photopigments after photon captured
-must be supplied by diet
-if deficient then problems seeing at night > degeneration of receptor outer segments = permanent blindness

Question 16

visual field losses

Answer 16

1. lesion optic nerve = ipsilateral monocular blindness
2. lesion optic chiasm = bitemporal hemianopsia
3. lesion optic tract = homonymous hemianopsia

Question 17

function of retinal projections to suprachiasmatic nuclei

Answer 17

aka retinohypothalamic pathway for circadian rhythm

Question 18

function of retinal projections to pretectal nuclei

Answer 18

for pupillary light reflex

Question 19

function of retinal projections to LGN

Answer 19

primary visual pathway
1. retinal ganglion cells
2. lateral geniculate nucleus
3. primary visual cortex/striate cortex in occipital lobe

Question 20

function of retinal projections to superior colliculi

Answer 20

coordinates head/eye movement to visual targets

Question 21

glaucoma

Answer 21

degenerative eye disease so loss of retinal ganglion cells
-inc intraocular pressure makes worse

Question 22

retinal detachment

Answer 22

separation of neural retina (photorecptors) from pigment epithelium
-diffusion distance inc so no nutrients/oxygen to retinal cells
-from trauma

Question 23

age related macular degeneration

Answer 23

loss of central vision but maintain peripheral
-smoking risk factor

Question 24

diabetic retinopathy

Answer 24

vasculature disease of retina
-in both type 1 and 2

Question 25

strabismus

Answer 25

developmental disease
-cross eyes/squint from failure of eyes to fixate on same point = double vision