unit 6

Question 1

Benefits of Binocular Vision

Answer 1

Single vision
* Stereovision - depth perception
* Increase field of vision
* Compensation for blind spot

Question 2

Fixation is

Answer 2

Image on fovea and Fixation reflexes to keep image on fovea

Question 3

Fusion is

Answer 3

single image formed with images from both
eyes

Question 4

Diplopia is

Answer 4

2 images are perceived; one from each eye;
lack of fusion

Question 5

Suppression

Answer 5

the brain ignores one of the images
during diplopia

Question 6

Amblyopia

Answer 6

reduced BCVA if the visual system in the
brain does not receive clear images during

Question 7

(BCVA

Answer 7

best corrected visual acuity

Question 8

Oculomotor Control e.g Saccades

Answer 8

Fast movements that keep the image on the
fovea

Question 9

Smooth pursuits

Answer 9

Slow movements of the eyes to follow an object

Question 10

Monocular

Answer 10

: includes abduction, adduction, supraduction,
infraduction, intorsion, extorsion

Question 11

Dextroversion

Answer 11

both eyes looking RIGHT

Question 12

Levoversion

Answer 12

both eyes looking LEFT

Question 13

Supraversions

Answer 13

both eyes looking UP

Question 14

Infraversion

Answer 14

: both eyes looking DOWN

Question 15

Convergence

Answer 15

both eyes look TOWARDS each other

Question 16

Divergence

Answer 16

: both eyes look AWAY from each other

Question 17

Names of EOMs

Answer 17

Superior rectus
* Inferior rectus
* Medial rectus
* Lateral rectus
* Superior oblique
* Inferior oblique

Question 18

Primary Action of EOMs

Answer 18

Elevation – SR
* Depression - IR
* Adduction - MR
* Abduction - LR
* Intorsion - SO
* Extorsion - IO

Question 19

Yoke muscles

Answer 19

muscles from each eye that work
together to move the eyes together

Question 20

Hering’s Law of Equal Innervation

Answer 20

when a muscle in
one eye is sent a message to move, the yoke muscle in the other eye receives equal
innervation.

Question 21

Sherrington’s Law of Reciprocal Innervation

Answer 21

when a
signal is sent to one muscle to contract the
opposing muscle for that eye is sent a signal to
relax.

Question 22

Strabismus Definition

Answer 22

the visual axis of the eyes are not aligned
and the eyes appear to be looking in different directions

Question 23

Amount of deviation : measured in prism diopters Direction of deviation:

Answer 23

eso, exo, hyper, hypo

Question 24

Esotropia

Answer 24

Inward deviation

Question 25

Exotropia

Answer 25

Outward deviation

Question 26

Hypertropia

Answer 26

Upward and downward deviation

Question 27

Causes of Strabismus

Answer 27

eye turning inwards due to the focusing efforts as the eyes try to see clearly.

Question 28

Congenital strabismus

Answer 28

(disease or physical disability present from birth) – may require surgery.

Question 29

Cranial nerve palsies

Answer 29

damage to one of the nerves ◦ e.g CN III, CN IV, CN VI

Question 30

Decompensated strabismus

Answer 30

develops as an adultlong standing deviation –previously well controlled by the motor fusional mechanism - now decompensating.

Question 31

more Causes of Strabismus

Answer 31

Brain damage ( supranuclear structures) * CN damage (oculomotor nuclei or nerves) * Direct EOM damage or muscle entrapment in orbital wall fractures

Question 32

Duane syndrome

Answer 32

incorrect innervation of the EOMs by the cranial nerves; congenital anomaly. Some muscles stretch when they should tighten, some stay loose when they should be contracting.

Question 33

Brown syndrome

Answer 33

: Problem with the SO tendon (too tight or too short) * usually congenital but could be secondary to trauma or surgery

Question 34

Hirschberg

Answer 34

Shine a light at the eyes and observe where the light reflex is located in reference to the pupil. For every mm that the light is decentered, the eye is turned about 15 diopters (7 degrees from center).

Question 35

Krimsky

Answer 35

Essentially the Hirschberg test, but with prisms employed to quantify amount of deviation. ◦ Determining how much prism is required to center the reflex. ◦ Modified Krimsky test = placing prism in front of fixing eye.

Question 36

Randot

Answer 36

vectograph random dot stereotest. ◦ Used for detecting amblyopia, strabismus and suppression, and for assessing stereoacuity. ◦ Can measure stereoacuity from 400 to 20 seconds of arc.

Question 37

Stereo fly

Answer 37

Purpose is to measure how minutely the two eyes can discern differences in the distances of objects from the observer.

Question 38

Dissociation tests: for diplopia / suppression

Answer 38

The Worth Four Light Test is also used in detection of suppression of either the right or left eye.

Question 39

Normal BSV: Px sees 4: red, 2 green and single white

Answer 39

Diplopia: Px sees 5: 1 red, 2 green and 2 white dots