Lecture 15 (dr. chase)

Question 1

what pathway causes accommodation of the ciliary muscle?

Answer 1

parasympathetic (Ach makes the muscle contract)

Question 2

what pathway causes the ciliary muscle to relax for distance viewing?

Answer 2

the sympathetic system (NE makes the muscles relax)

Question 3

what happens to the lens shape as we accommodate?

Answer 3

the lens bulges

Question 4

what is depth of field?

Answer 4

the amount a target can be moved and still give a clear image on the retina

Question 5

what is depth of focus?

Answer 5

the range on the retina where an image will still be clear

Question 6

what is the monocular DOF range?

Answer 6

from 0.46 to 0.81

Question 7

what happens to depth of focus as the pupil diameter increases?

Answer 7

the depth of focus gets smaller (a smaller pupil has a larger depth of focus)

Question 8

does the push-up method overestimate or underestimate accommodation?

Answer 8

overestimates (by 2D)

Question 9

does retinoscopy overestimate or underestimate?

Answer 9

it overestimates accommodation (by 2D)

Question 10

what is the hofstetter equation for the average amplitude of accommodation?

Answer 10

18.5 - 0.3age

Question 11

what happens to the push-up amplitude with age?

Answer 11

it gradually decreases - about 0.25D every year you age

Question 12

what is the equation for Hofstetter’s minimum amplitude of accommodation?

Answer 12

15 - 0.25age

Question 13

what predicts symptom severity of amplitude of accommodation?

Answer 13

only accommodative lag

Question 14

what is seen with static accommodative target?

Answer 14

under-accommodation or lag

Question 15

how much accommodation can a person with accommodative insufficiency use until they cannot function anymore?

Answer 15

about 3D - need a 4-5D stimulus to really push their system and see it clinically

Question 16

does accommodative insufficiency have a steady, constant accommodative lag?

Answer 16

no - it is very unstable and the target is always blurry

Question 17

does a patient with accommodative fatigue or ill-sustained accommodative have a constant lag?

Answer 17

no - over time they have a larger lag as the time increases

Question 18

what is a normal cpm for accommodative facility for monocular and binocular?

Answer 18

monocular = 10 cpm
binocular = 8 cpm

Question 19

what is the normal result for an amplitude-scaled facility test (binocular) - adjusted for distance and lens power?

Answer 19

binocular = 14cpm

Question 20

how does tonic accommodation affect the facility test?

Answer 20

some people have 2.5D of tonic accommodation (instead of 0D) and the flipper will not change accommodation stimulus

Question 21

what is the far-near response seen by autorefraction?

Answer 21

initially the eyes will lead (over accommodate) then they will lag by about 1D while viewing a target

Question 22

what is accommodative gain?

Answer 22

parasympathetic (cholinergic), muscarinic receptor in ciliary muscle and has a 1-2 sec response time

Question 23

what is slow adaptation?

Answer 23

sympathetic (adrenergic), beta2 receptor in ciliary smooth muscle, 20-40 sec response time and has low magnitude (1.5-2D max)
inhibitory signal is dependent upon parasympathetic gain

Question 24

when does the amplitude of accommodation start decreasing?

Answer 24

after age 30 (35-40 = critical ages for presbyopia)

Question 25

why do myopes maintain better amplitudes?

Answer 25

myopia reduces the amount of accommodation needed - system is already focused at near

Question 26

which is responsible for presbyopia - the lens or ciliary muscle?

Answer 26

lens = becomes crystalized and looses elasticity (no a linear decline)

Question 27

when do you treat presbyopia?

Answer 27

when the patient complains of symptoms (asthenopia)

Question 28

does amplitude predict symptoms?

Answer 28

no - only accommodative lag