Ocular Motility CH10

Question 1

Positioning the eyes so that an object’s image is placed on the macula is known as:
a) fixation
b) binocular vision
c) stereo vision
d) depth perception

Answer 1

a) In fixation, the eyes are positioned so that each macula is receiving the same image
(albeit at a slightly different angle).

Question 2

The coordinating process by which the two images (one received by each eye) are
blended into a single image is known as:
a) stereo vision
b) depth perception
c) binocular vision
d) fusion

Answer 2

d) The brain merges the slightly different images coming from each eye to create a single three-dimensional image. This is known as fusion.

Question 3

Coordinated movement of both eyes in the same direction is known as:
a) ductions
b) versions
c) rotations
d) saccades

Answer 3

b) Versions are movements of both eyes in the same direction. Ductions are movements of
one eye alone.

Question 4

Which of the following are not considered cardinal positions of gaze?

a) down and left, or up and left
b) up and right, or down and right
c) straight ahead, or straight up or down
d) directly left, or directly right

Answer 4

c) Straight ahead (primary gaze), straight up, and straight down are not cardinal positions
of gaze. In any of these positions, the action of one muscle can be masked by the action of
another, so these positions are not considered diagnostic.

Question 5

When testing a patient’s versions, it is important to:
a) test in dim lighting
b) keep the patient’s head still
c) use an opaque occluder to break fusion
d) keep the patient’s eyes in primary position

Answer 5

b) When testing versions (range of motion), it is important that the patient keep his or her
head still. If the patient moves the head to follow the target, you are not able to test the full motion of the eyes, but rather the range of motion of the neck! The test is done in room
light so you can see the eyes as they move. An occluder is not used when testing versions.
If the eyes remained in primary position, they would not move at all.

Question 6

Versional movements are those that:
a) result in fusion
b) move one eye
c) move both eyes in the same direction
d) move both eyes in a different direction

Answer 6

c) Versions move both eyes in the same direction. Fusion does not necessarily occur; for example, the muscles in a blind eye are still innervated and linked to those of the other
(seeing) eye.

Question 7

If the eyes have normal version movements, all of the following will exist except:

a) each eye will move with equal speed
b) each eye will move smoothly
c) the eyes will diverge equally
d) each eye will be in the same position relative to the other

Answer 7

c) Divergence is when the eyes move in opposite directions, away from each other. In versions, the eyes are moving together in the same direction. (Be sure to read questions carefully—there is a difference between versions and vergences.)

Question 8

To test the right inferior rectus (RIR) and the left superior oblique (LSO) muscles, the
patient must look:
a) directly right
b) down and to the right
c) up and to the right
d) down and to the left

Answer 8

b) Looking down and right (from the patient’s perspective) requires the RIR and LSO.
Straight ahead (primary gaze) is not diagnostic. RSR and LIO are up and right. RSO and LIR
are down and left (Figure 10-2).

Question 9

Your patient is looking down and to the left. Which muscles are pulling the eyes into
this position?

a) RIR and LSO
b) Right superior oblique (RSO) and left inferior rectus (LIR)
c) Right superior rectus (RSR) and left inferior oblique (LIO)
d) Right inferior oblique (RIO) and left superior rectus (LSR)

Answer 9

b) In down and left gaze, the RSO and LIR are being used. RIR and LSO would be down
and right. RSR and LIO are up and right. RIO and LSR are up and left.

Question 10

You want to check the action of the right lateral rectus (RLR) muscle. Where do you
direct the patient to look?
a) to the left
b) to the right
c) down and right
d) up and left

Answer 10

b) The RLR has its primary action in right gaze. Left gaze would be the RMR. Down and
right would be RIR, and up and left would be RIO.

Question 11

You want to check the action of the LIO muscle. Where do you direct the patient to
look?
a) to the left
b) down and right
c) up and left
d) up and right

Answer 11

d) To check the action of the LIO, have the patient look up and right. Left gaze would check the LLR. Down and right would be the LSO, and up and left would be the LSR.

Question 12

Ductions refer to:

a) muscles that work against each other during eye movements
b) movements of one eye
c) movements of both eyes in the same direction
d) movements of both eyes in the opposite direction

Answer 12

b) Ductions refer to movements of one eye. Muscles that work against each other in the
same eye are antagonists. Movements of both eyes in the same direction are versions.
Movements of both eyes in opposite directions are vergences.

Question 13

Testing ductions is useful in differentiating cases of:
a) restrictive strabismus
b) accommodative strabismus
c) congenital esotropia
d) pseudostrabismus

Answer 13

a) Testing ductions is useful when one eye is at fault for a deviation, as in restrictive stra-
bismus. In answers b through d, it would be more helpful to test versions.

Question 14

If one eye is obviously turned in, out, up, or down when you perform a simple external
evaluation of the patient, this deviation is a:
a) ptosis
b) phoria
c) tropia
d) vergence

Answer 14

c) Unless it is intermittent, a tropia is there all the time. If you can look at the patient and
see that one eye is turned, it is a tropia. A phoria is evident only when you cover one eye
or otherwise disrupt fusion. Ptosis is a drooped eyelid.

Question 15

A phoria is exhibited when:

a) the patient is malingering
b) fusion is disrupted
c) the patient is fusing
d) the patient has diplopia

Answer 15

b) A phoria is evident only when you disrupt fusion. (Note: Some phorias “break down”
when the patient is tired. This is actually an intermittent deviation.)

Question 16

The difference between a phoria and an intermittent tropia is:

a) the patient experiences diplopia with the phoria but not with the intermittent tropia
b) the phoria rarely is controlled, and the intermittent tropia always is controlled
c) the phoria usually is controlled, and the intermittent tropia always is uncontrolled
d) the phoria usually is controlled, and the intermittent tropia sometimes is controlled

Answer 16

d) A phoria usually is controlled unless fusion is disrupted. When the disruption is removed,
the eyes will fuse again. An intermittent tropia comes and goes; sometimes the patient is
fusing, and sometimes he or she is not. When the patient is not fusing, the deviation
appears.

Question 17

An adult patient with a tropia has either:

a) amblyopia or anisometropia
b) prism or slab-off lenses
c) diplopia or suppression
d) fusion or stereopsis

Answer 17

c) An adult with a crossed eye either has learned to suppress the image from the eye that is not fixating or has double vision. Usually, suppression is learned in childhood as the visual system is developing; the brain learns to ignore the image from a crossed eye. In cases where the strabismus occurs as an adult, diplopia occurs because the brain does not know how to suppress a second image. It is not a given that amblyopia or anisometropia exist, although they might. Fusion and stereopsis can occur only when both eyes are working together, looking at the same object.

Question 18

Label the following on Figure 10-1:

*esotropia
*hypotropia
*exotropia
*orthophoria
*hypertropia

Answer 18

B: esotropia
E: hypotropia
D: exotropia
A: orthophoria
C: hypertropia

Question 19

An intermittent horizontal tropia might be aggravated by all of the following except:
a) inattention
b) dry eye
c) illness
d) fatigue

Answer 19

b) In the other 3 cases, there is simply not enough effort/strength to maintain fusion.

Question 20

Vertical deviations are conventionally described by indicating:

a) the higher (up-turned) eye
b) the lower (down-turned) eye
c) the preferred eye
d) the eye with best vision

Answer 20

a) Conventionally, vertical deviations are described as a hypertropia of the higher eye.
Thus, if the patient was fixating with the right eye and the left eye was deviated downward,
the right eye is higher. So this situation would be designated as a right hypertropia (RHT).

Question 21

In pseudostrabismus:

a) the eye turns only if fusion is disrupted
b) the eyes are straight, but there is amblyopia
c) the eyes are straight, but the patient has diplopia
d) the eyes look crossed, but actually are straight

Answer 21

d) The prefix “pseudo” means false. Thus, pseudostrabismus is false strabismus; the eyes falsely appear to be crossed although they are straight.

Question 22

Pseudostrabismus usually is seen in:
a) boys
b) girls
c) infants
d) adults

Answer 22

c) Because infants have a flat nasal bridge and (sometimes) epicanthal folds, they are impli-
cated more often in pseudostrabismus (an optical illusion of esotropia) than any other
group. There is no indication whether boys or girls are most often affected.

Question 23

The most common patient complaint in a new nerve palsy is:
a) decreased vision
b) diplopia
c) an ache in the affected muscle(s)
d) an inability to read at near

Answer 23

b) An adult or child with a new nerve palsy notices double vision. (A child with a con-
genital nerve palsy learns to suppress one image and does not see double.)

Question 24

Nerve palsies cause the affected muscle(s) to become:
a) overactive
b) underactive
c) spasmodic
d) responsive

Answer 24

b) If the muscle is not getting a full nerve supply, it will not be able to react properly (if at all). It will thus be underactive. This might manifest itself as an overaction of the muscle’s
antagonist (the muscle in the same eye that has the opposite action).

Question 25

The purpose of covering one eye with an occluder for strabismus screening is to:
a) determine if the patient is suppressing
b) perform monocular testing
c) disrupt fusion
d) determine if the patient is malingering

Answer 25

c) The occluder is used in strabismus cover tests to disrupt fusion (ie, to prevent the eyes
from being locked onto the same target). Fusion will hold a phoria and often an intermittent deviation in check, so fusion must be disrupted in order to determine if these deviations exist.

Question 26

Cover testing can be performed even on an infant because:
a) it is nonthreatening
b) it is painless
c) it is objective
d) it is brief

Answer 26

c) The cover tests are objective; they are based on the observations of the examiner rather
than on the responses of the subject. Thus, they can be performed on an infant or any other patient who cannot or will not give a verbal response.

Question 27

Cover testing can be useful in all of the following patients except:
a) bilateral aphake
b) bilateral pseudophake
c) the patient with suppression
d) the monocular patient

Answer 27

d) There is no point in doing cover tests on a monocular patient because there is no vision
in the second eye with which to fuse. The patient must always fixate with the single, seeing eye.

Question 28

The cover/uncover test is used to determine the presence of:

a) phoria versus tropia
b) amblyopia
c) suppression
d) stereopsis

Answer 28

a) The cover/uncover test differentiates between a phoria and a tropia.

Question 29

The cover/uncover test can also reveal the presence of:
a) esotropia versus exotropia
b) vergence insufficiency
c) depth perception
d) visual acuity

Answer 29

a) The cover/uncover test also indicates the direction of any deviation (ie, eso-, exo-, or
vertical deviation).

Question 30

You have covered the patient’s right eye. When you uncover it, the right eye moves
inward. Now, you cover the left eye. When you uncover it, the left eye moves inward.
At this point, you can only deduce that the patient has an:
a) exophoria
b) exotropia
c) exodeviation
d) esodeviation

Answer 30

c) The eyes must have drifted out (ie, toward the temple) under the cover if they make
inward movements when uncovered, so an exodeviation is present. You were not given
enough information to differentiate between a phoria and tropia. For that, you need to know
what the uncovered eye is doing, as well.

Question 31

The patient’s vision is 20/20 in both eyes. You cover the patient’s right eye and note
that when you do so, the left eye moves outward. When you uncover the right eye,
neither eye moves. When you cover the left eye, the right eye moves outward. When
you uncover the left eye, neither eye moves. This indicates:

a) alternating exotropia
b) esophoria
c) intermittent esotropia
d) alternating esotropia

Answer 31

d) An outward motion upon uncovering indicates that the eye has drifted in, denoting an esodeviation. In this case, regardless of which eye is covered, the covered eye drifts in.
When the eye is uncovered, it does not move to take up fixation (indicating a tropia). This
further indicates that the patient is willing to use either eye to fix, revealing an alternating
esotropia.

Question 32

During the cover/uncover test, if a patient has a phoria, the response of the eye that is
not covered is to:
a) take up fixation
b) move in the same direction as the covered eye
c) remain straight
d) deviate in or out

Answer 32

c) In a phoria, the eye under the cover drifts. The eye that is not covered is fixating. When
you remove the cover, the resulting diplopia causes the deviated eye to move in order to
pick up fixation. The eye that was not covered is fixating already, so it does not need to
move. Be sure to read the questions carefully; the answer would have been different if this
had been a cross cover test.

Question 33

The alternate (cross) cover test does not reveal:
a) exodeviations
b) esodeviations
c) hyper deviations
d) a phoria versus a tropia

Answer 33

d) The alternate (or cross) cover test will reveal horizontal and vertical deviations, but does
not differentiate between a phoria and a tropia.

Question 34

When performing the alternate (cross) cover test, it is important to:
a) momentarily remove the cover from one eye before covering the other
b) move the cover rapidly from one eye to the other
c) allow the patient to look at the target with both eyes before covering again
d) move the cover from one eye to the next every half-second

Answer 34

b) When performing the alternate (cross) cover test, move the cover rapidly from one eye
to the other, but every half-second is too fast. The important thing is to prevent the patient
from seeing with both eyes at once and thus regaining fusion.

Question 35

If there is no movement of either eye during any part of the alternate (cross) cover
test, one has determined that:

a) the patient is amblyopic in one eye
b) the eyes are orthophoric
c) the patient has stereo vision
d) the patient has equal vision in both eyes

Answer 35

b) If no motion is seen during the alternate (cross) cover test, it is logical to assume that the patient is orthophoric. You cannot, however, assume that amblyopia does or does not exist, that the patient has stereopsis, or that vision is equal in both eyes.

Question 36

You have performed the alternate (cross) cover test and notice that each eye moves
inward when uncovered. What is your next step?

a) record exodeviation in the chart
b) record exotropia in the chart
c) record esodeviation in the chart
d) perform a cover/uncover test

Answer 36

d) The only thing you know at this point is that there is some type of exodeviation. (For the
eye to move inward when it is uncovered, it must have drifted outward under the cover.)
Once you have found movement on the alternate (cross) cover test, use the cover/uncover test to determine if it is a tropia or a phoria.

Question 37

The alternate (cross) cover test can be used to measure the size of a deviation if:

a) the patient can fuse
b) the corneal reflex can be seen
c) it is combined with prisms
d) polarized glasses are used

Answer 37

c) The alternate (cross) cover test combined with prisms to measure the size of a deviation
(phoria or tropia) becomes the “prism and cover test.” The deviation can be measured in a patient with fusion because the test itself disrupts fusion. The corneal reflex and polarized glasses are not used in the prism and cover test.

Question 38

Which of the following is not a component of binocular vision?

a) clear vision in each eye
b) alignment of the eyes
c) overlapping visual fields
d) identical images on each retina

Answer 38

d) Binocular vision depends on slightly different images coming from each retina. (That was tricky!)

Question 39

Depth perception:

a) requires two eyes
b) requires overlapping visual fields
c) is absent in monocular patients
d) uses environmental “clues”

Answer 39

d) Depth perception is not the same as binocular, or stereo, vision. A person with one eye can develop depth perception by learning to use “clues” from the environment, such as
overlap, grayness, or merging.

Question 40

Stereopsis is recorded in:

a) Snellen fractions
b) degrees of arc
c) seconds of arc
d) degrees of field

Answer 40

c) Stereopsis is measured in seconds of arc.

Question 41

Which of the following indicates the better stereo vision?

a) 50 degrees of arc
b) 25 degrees of arc
c) 50 seconds of arc
d) 25 seconds of arc

Answer 41

d) Twenty-five seconds of arc indicates finer stereo discrimination than 50 seconds of arc.
Stereo vision is not measured in degrees of arc as given in answers a and b.

Question 42

Stereopsis can be elicited and measured in which of the following patients?

a) 60 diopter esotropia
b) 45 diopter exotropia
c) 8 diopter intermittent exotropia
d) monocular

Answer 42

c) A patient with a constant esotropia or exotropia over 10 degrees will not have stereo
vision, nor will a monocular patient. A binocular patient with an intermittent deviation, a phoria, or a deviation of 10 degrees or less should have a stereo acuity test performed.

Question 43

Stereopsis differs from depth perception in that:
a) depth perception is monocular or binocular
b) stereo vision involves judging spatial relationships
c) depth perception involves seeing in three dimensions
d) stereopsis is a learned experience

Answer 43

a) Stereopsis is present only in binocular individuals. Depth perception, however, exists in binocular and monocular patients. Answers b and c are backwards: stereo vision involves
seeing in three dimensions, and depth perception involves judging spatial relationships. Stereopsis is not learned; depth perception is.

Question 44

While it does not give a measurement, a simple stereo test that can be done at bedside
is the:
a) Hirschberg test
b) confrontation stereo test
c) pencil point to pencil point test
d) Amsler grid stereo test

Answer 44

c) Having the patient touch one pencil point to another is an indicator of gross stereopsis.
(Try it on yourself: once with both eyes opened and once with one eye closed.) The Hirsch-
berg estimates the size of a deviation, not stereopsis. Answers b and d are contrived.

Question 45

The Titmus/Wirt test, Randot test, and fly test all use:
a) polarized glasses
b) glasses with one red and one green lens
c) dissociating prisms
d) a red filter

Answer 45

a) Each of the tests listed used polarized glasses.

Question 46

You ask a cooperative 3-year-old girl to touch the wings of the Titmus fly. She recoils
and refuses. You can assume that most likely:

a) she is tired and cranky
b) she has impaired mental ability
c) she has at least gross fusion
d) she has an intermittent deviation

Answer 46

c) The fly was chosen as a test object because it is repulsive. An otherwise cooperative child
may refuse to touch the fly because it is ugly and appears to be real. When the child sees
it, the huge fly seems to be standing on the page. Refusal is generally considered a positive indication that gross stereopsis exists, but further testing is indicated.

Question 47

You are testing an intelligent 12-year-old boy with the Titmus/Wirt circles and suspect
that he is either a good guesser or a cheater. You should:
a) turn the test 90 degrees
b) turn the test 180 degrees
c) switch the glasses around
d) record the patient’s responses regardless

Answer 47

b) Turning the test around 180 degrees will change the location of the stereo rings and make them appear sunken instead of elevated. If you turn the test 90 degrees, it will not be stereopic. Polarized glasses are usually designed to be worn only one way. It is in the patient’s best interest to get the most accurate measurement possible.

Question 48

An advantage of the Random Dot E test over the Titmus test is that the Random Dot E:
a) does not require special glasses
b) offers monocular clues
c) does not offer monocular clues
d) does not require color vision

Answer 48

c) The first 3 rings of the Titmus/Wirt test can be guessed correctly by a nonfussing patient
because the dots look off-center. The Random Dot E test offers no such clues. Neither test
requires accurate color vision.

Question 49

Rhythmic jerking motions of the eyes are known as:
a) versions
b) ductions
c) nystagmus
d) end-point/gaze-induced

Answer 49

c) Nystagmus is rhythmic jerking of the eyes. This movement may be horizontal, vertical,
or torsional.

Question 50

When evaluating congenital nystagmus, all of the following might be noted except:
a) binocular or monocular
b) direction
c) magnitude
d) head position

Answer 50

a) Because of the laws of extraocular muscle innervation, the eyes of a patient with con-
genital nystagmus will both jerk. The direction of the jerking should be noted (see answer 49) as well as the magnitude (eg, small, fine movements versus large ones). In some
patients, the jerking is lessened when the eyes are in a specific position, so the patient may
adopt a head tilt or turn to quiet the eyes.

ANSWER 49: Nystagmus is rhythmic jerking of the eyes. This movement may be horizontal, vertical, or torsional.

Question 51

A patient with nystagmus might find that which of the following decreases the magni-
tude of the jerking?

a) closing/covering one eye
b) squinting
c) positioning the head
d) wearing sunglasses

Answer 51

c) See answer 50. In some cases, occluding one eye makes the nystagmus worse.

ANSWER 50: Because of the laws of extraocular muscle innervation, the eyes of a patient with con-
genital nystagmus will both jerk. The direction of the jerking should be noted (see answer 49) as well as the magnitude (eg, small, fine movements versus large ones). In some
patients, the jerking is lessened when the eyes are in a specific position, so the patient may
adopt a head tilt or turn to quiet the eyes.

Question 52

A head position in which the nystagmus is quietest (least) is known as the:

a) null point
b) near point
c) angle of deviation
d) cyclic amplitude

Answer 52

a) The null point is when the head is in a position where the jerking is “most nullified” or
lessened (ie, quieter).

Question 53

During visual acuity testing and refractometry, it is important to remember that
which of the following might cause a worsening of nystagmus?
a) fogging
b) occluding one eye
c) cross cylinder
d) astigmatic dial

Answer 53

b) Occluding one eye can make the nystagmus worse. Use a +6.00 to “occlude” (fog) the
eye not being examined in visual acuity testing and refractometry.

Question 54

Your physician plans to prescribe glasses for a patient with nystagmus. Which method
will give her the best information?
a) autorefractor alone
b) retinoscopy alone
c) phoroptor measurement
d) trial frames and lenses

Answer 54

d) Using a trial frame for refractometry will allow the patient to easily adopt his or her
null-point head position. This is not as easily done using the phoroptor. Subjective refractometry (versus autorefractor or retinoscopy alone) will provide the best information from
which the practitioner might prescribe.

Question 55

A type of nystagmus that a normal patient might exhibit in far right or far left gaze
is:
a) ductional nystagmus
b) versional nystagmus
c) acquired nystagmus
d) gaze-induced nystagmus

Answer 55

d) Gaze-induced nystagmus (also called end-gaze and end-point nystagmus) sometimes
appears when the patient moves the eyes out of primary position, usually to the right or left.

Question 56

Adult-onset nystagmus will frequently cause the patient to complain of:
a) diplopia
b) “vibrating” vision
c) photophobia
d) extraocular muscle pain

Answer 56

b) Vibrating vision (properly termed oscillopsia) is where objects of regard seem to move, jerk, or wiggle when the patient concentrates on them. This phenomenon occurs only in acquired nystagmus; patients with congenital nystagmus do not have this symptom.

Question 57

Which of the following is not true regarding congenital nystagmus?
a) It is often associated with maternal infections.
b) The child may adopt a specific head position.
c) The child will frequently outgrow the condition.
d) It is often associated with visual impairment.

Answer 57

c) In some cases, the nystagmus will resolve as the child grows; however, that is not the
case with most types of nystagmus. The other statements are true. The head position is
adopted in order to move the eyes into a position where the jerking is quieter or stopped, called the “null point,” giving the patient clearer vision. The patient “finds” this position (which varies from patient to patient) at an early age, generally when beginning to sit up or stand. In addition, congenital nystagmus is often associated with lesions in the optic system.