Pediatric Eye Exam, EOM Anatomy, Visual Motor and Sensory Physiology, and Amblyopia

Question 1

Preferred method of teting visual acuity in amblyopic patient

Answer 1

crowded optotypes

Question 2

what age is fixation obtained

Answer 2

4 months

Question 3

dilating and cycloplegic drops of choice for kids? how long will they last?

Answer 3

1% cyclopentolate (0.5% cyclopentolate for infants), and phenylephrine. cyclopentolate lasts 6-24 hrs

Question 4

what is consecutive strabismus

Answer 4

a strabismus that is in the opposite direction of a previous strabismus (for example, exo after surgery for eso)

Question 5

distances of rectus insertions from limbus? where do the rectus muscles penetrate Tenon’s?

Answer 5

MR 5.5
IR 6.5
LR 6.9
SR 7.7
Insert 10 mm posterior to their insertions

Question 6

origins of each EOM

Answer 6

• all rectus muscles originate a the annulus of Zinn
• SO originates above the annulus of Zinn, but functional origin is trochlea
• IO originates on periosteum of inferonasal maxillary bone, adjacent to anterior lacrimal crest
• Levator orginates above annulus of Zinn

Question 7

directions of pull for each EOM w/ respect to visual axis

Answer 7

• MR and LR 90 degrees
• SR and IR 23 degrees
• IO and SO 51 degrees

Question 8

EOM with longest tendon? shortest tendon? longest arc of contact?

Answer 8

longest tendon: SO (26 mm)
shortest tendon: IO (1 mm)
longest arc of contact: IO (15 mm)

Question 9

positions of obliques with respect to vertical rectus muscles

Answer 9

obliques are inferior to corresponding rectus muscles

Question 10

blood supply to EOMs

Answer 10

• lateral muscular branch of the ophthalmic artery supplies LR, SR, SO, LPS. LR receives additional supply from lacrimal artery
• medial muscular branch of ophthalmic artery supplies MR, IR, IO
• the muscular branches then also give off anterior ciliary arteries that supply the anterior segment

Question 11

location of vortex veins

Answer 11

at nasal and temporal borders of inferior and superior rectus muscles; one is always in the inferotemporal quadrant just posterior to the IO tendon, and another is always in the superotemporal quadrant just posterior to the SO tendon

Question 12

venous drainage of the EOMs

Answer 12

parallels arterial supply; drain into superior and inferior orbital veins

Question 13

location of adipose tissue in orbit?

Answer 13

extraconal: stops 10 mm from limbus
intraconal: separated from sclera by Tenon’s (Tenon’s prevents fat from scarring to globe)

Question 14

only EOM not to originate at orbital apex

Answer 14

inferior oblique

Question 15

what does Tenon’s fuse with anteriorly and posteriorly

Answer 15

anterior: intermuscular septum
posterior: optic nerve sheath

Question 16

what to the inferior oblique and inferior rectus pulleys combine to form, and what is attached to this conjoined structure

Answer 16

combine to form Lockwood ligament; neurofibrovascular bundle containing the inferior oblique motor nerve is attached

Question 17

how long are the recuts muscles?

Answer 17

40 mm each

Question 18

where do their motor nerves penetrate the SR and SO?

Answer 18

one third of the way from origin to insertion (about 26 mm posterior to insertion)

Question 19

what nerve is not affected by a properly performed retrobulbar anesthetic?

Answer 19

trochlear nerve (lies outside muscle cone)

Question 20

injury to the inferior oblique motor nerve may also affect what other structure?

Answer 20

parasympathetic fibers to pupillary constrictor and ciliary muscle run alongside this nerve, so mydriasis and loss of accommodation can occur with injury

Question 21

which is the only rectus muscle without an oblique muscle running tangential to it?

Answer 21

MR

Question 22

effect of IR and SR resection and recession on palpebral fissure?

Answer 22

• IR resection narrows PF by lower lid elevation
• IR recession widens PF by lower lid retraction
• SR resection can narrow PF by lower upper lid
• SR recession generally has no effect on PF

Question 23

most common cause of unilateral visual impairment in American adults younger than 60

Answer 23

amblyopia

Question 24

T or F regarding amblyopia:

1. peripheral vision is relatively spared
2. amblyopia from refractive error occurs earlier and is more progressive than other causes
3. receptive fields of vision in amblyopic eye are abnormally small
4. amblyopic patients have better visual acuity when measured with crowded optotypes compared to uncrowded optotypes

Answer 24

1. true
2. false; amblyopia from media opacity presents first and progresses more quickly
3. false; receptive fields are larger
4. false; because receptive fields are larger, there is more difficulty with crowded optotypes

Question 25

what is grating acuity, and what type of amblyopia is this affected abnormally compared to the other types?

Answer 25

the ability to detect patterns of uniformly spaced stripes; this is tested in Teller Acuity Cards and LEA Grating Acuity Test. Grating acuity is affected LESS than normal optotypes in strabismic amblyopia compared to the other types of amblyopia

Question 26

what is the neutral density filter effect as applies to amblyopia?

Answer 26

slower decrease in visual acuity when a neutral density filter is placed before the strabismic amblyopic eye compared to eyes with organic disease

Question 27

a patient with amblyopia has a decentered corneal light reflex in the amblyopic eye when the good eye is covered. what doe this indicated, and what is the approximate visual acuity in this eye?

Answer 27

this indicates eccentric fixation, where light is focused onto a nonfoveal region of there retina; this implies 20/200 or worse and portends worse prognosis for visual recovery

Question 28

levels of anisometropia that can lead to amblyopia

Answer 28

1.50 D anisohyperopia, 2.00 D anisoastigmatism, 3.00 D anisomyopia

Question 29

what is isoametropic amblyopia? what levels of refractive error can lead to this type of amblyopia?

Answer 29

large, uncorrected, approximately equal refractive error in both eyes. 2-3 D cycl, 4-5 D hyperopia, 5-6 D myopia

Question 30

what is reverse amblyopia?

Answer 30

amblyopia to the fellow eye that occurs after patching

Question 31

when should visually significant congenital cataracts be removed?

Answer 31

by 4-6 weeks after birth, to prevent amblyopia

Question 32

part time occlusion guidelines for amblyopia

Answer 32

2-6 hours / day | 6 hours / day for severe (20/100-20/400)

Question 33

follow-up interval after visit when patching was initiated

Answer 33

2-3 months

Question 34

desired endpoint of therapy for unilateral amblyopia?

Answer 34

free alternation of fixation or visual acuity no more than 1 line difference between two eyes

Question 35

can patching be effective past first decade of life?

Answer 35

yes, especially if no patching had been tried previously

Question 36

is pharmacologic penalization useful in amblyopia treatment? which patient subset would benefit less from this method?

Answer 36

yes; atropine as effective as part time patching for mild to moderate amblyopia (20/100 or better); can be administered daily, but weekend administration is as effective for mild cases. less effective for myopes, because they don't rely on accommodation for clear distance vision

Question 37

side effects of full time patching

Answer 37

reverse amblyopia and strabismus

Question 38

if no visual improvement is obtained despite occlusive therapy with good adherence, after how long is treatment generally discontinued

Answer 38

3-6 months, but varies

Question 39

percentage of patient whose amblyopia regresses after treatment cessation?

Answer 39

33%

Question 40

what is Sherrington's law? what is an example of a violation of this law?

Answer 40

innervation to agonist causes recirprocal decrease in innervation to antoginst; Duane's syndrome violates this as MR and LR fire simulataneously

Question 41

Primary, secondary, and tertiary actions of each EOM

Answer 41

MR: 1 adduction; no additional actions LR: 1 abduction; no additional actions IR: 1 depression, 2 excyclotorsion, 3 adduction SR: 1 elevation, 2 incyclotorsion, 3 adduction IO: 1 excyclotorsion, 2 elevation, 3 abduction SO: 1 incyclotorsion, 2 depression, 3 abduction

Question 42

what gaze positions purely isolate the primary and secondary action of the SR, IR, SO, IO

Answer 42

- at 23 degrees of abduction, SR is pure elevator and IR is pure depressor; conversely, 90 degrees away at 67 degrees adduction these muscles are purely cyclotorsional - at 39 degrees of abduction, the oblique muscles are pure torsional muscles, and at 51 degrees of adduction they are pure elevators/depressors

Question 43

what is Hering's law, and what is an example of a violation of this law?

Answer 43

law of equal innervation, where yoke muscles in two eyes receive equal innervation (example: left MR and right LR have equal innervation on right gaze). DVD violates this

Question 44

primary v secondary deviation in paralytic or restrictive strabismus

Answer 44

primary is when better eye is fixating, secondary is when worse eye is fixating. because of Hering's law, secondary deviation is always larger

Question 45

5 types of convergence

Answer 45

accommodative, fusional, tonic, proximal/instrumental, voluntary

Question 46

magnocellular v parvocellular v koniocellular

Answer 46

magnocellular in periphery and detect motion but relatively insensate to color; parvocellular in fovea and detect high resolution; koniocellular involved in color vision, esp blue-yellow

Question 47

gestational time and amount of maximum number of retinal ganglion cells? final number of ganglion cells?

Answer 47

2.2-2.5 million by week 18, then decrease to 1.0-1.5 million by early postnatal life

Question 48

approximate visual acuity of newborn

Answer 48

20/400

Question 49

the more dissociating the test, the ____ likely the test will produce normal retinal correspondence

Answer 49

more

Question 50

name the tests for anomalous retinal correspondence in order of most to least dissociating

Answer 50

afterimage test, Worth 4-dot, red-glass test, amblyoscope, Bagolini striated glasses

Question 51

what is paradoxical diplopia?

Answer 51

temporary diplopia in a post-strab patient with ARC; refoveation occurs and the diplopia typically is temporary

Question 52

what is monofixation syndrome

Answer 52

peripheral fusion with the absence of bifoveal fusion due to a suppressive central scotoma