Introduction to BSV, Space perception and physiology of ocular movements

1. Introduction to BSV
Space perception and Physiology of
ocular movements
By - Krishna Banjade
Consultant optometrist
M. Optom
FLVPEI - Pediatrics and BSV

2. • Monocular vision - Use of one eye for one visual field.
Eg- A frog sees left visual field with left eye and right visual
field with right eye
• Biocular vision - Two eyes are used at a time but no
coordination in between
• Binocular vision - Coordinated vision from two eyes

3. Development of Binocular vision
• Up to 2 months - Monocular fixation
• Use of monocular cues
• Binocular fixation emerges at the beginning of 3rd month
• Vergences develop after 3 months of age
• Stereopsis develops at 4 months of age
• NPC present at 6 months

4. Development of Accommodation
• Newborns can focus accurately up to 75 cm
• At 1 month infant accommodates up to 19cm
• Proper accommodation at 4 months (10cm)
• Depth of focus greater at 1 month – smaller eyes and pupil
• Depth of focus decreases with improvement in
accommodation

5. Development of ocular movements
• Seen beneath the fused lids of fetus even at the gestational
age of 16 weeks
• Saccades and Pursuits elicited at 2 months

6. • Longest extraocular muscle
• Shortest extraocular muscle
Superior Oblique .
Also it is the thinnest
Inferior oblique.
Also it does not
originate from
annulus of zinn

7. EOM actions
Muscle Primary Secondary Tertiary
MR Adduction
LR Abduction
SR Elevation Intorsion Adduction
IR Depression Extorsion Adduction
SO Intorsion Depression Abduction
IO Extorsion Elevation Abduction

8. Ways to remember
• Superior – Intort
• Obliques - Abduct

9. Lateral rectus muscle is innervated by
a. Trochlear nerve
b. Abducens nerve
c. Oculomotor nerve
d. All of the above
LR6, SO4

10. True statements about the superior oblique muscle
include:
a. it originates at the lesser wing of the sphenoid bone
b. it is innervated by the fourth cranial nerve on its
upper surface
c. the muscle turns tendinous before entering the trochlea
d. it passes beneath the superior rectus muscle to insert
onto the globe
e. it inserts on the globe at 450 to the visual axis

11. Agonist
Any particular EOM producing a specific ocular movement
Synergist
Two muscles moving an eye in the same direction
Antagonist
The muscles having opposite action in the same eye
Yoke muscle (Contralateral synergists)
A pair of muscle one in each eye which contract simultaneously
during version movement E.g.: RLR and LMR in dextroversion
Contralateral Antagonist
A pair of muscles, one in each eye having opposite action eg. RLR
& LLR

12. In abduction of the right eye which statement is
wrong
a. The right lateral rectus muscle is the agonist
b. The right superior and inferior oblique muscles are the synergists
c. The right medial, superior, and inferior recti are the antagonists.
d. Yoke muscle to right lateral rectus muscle is left lateral rectus

13. Hering’s law of equal Innervations
Clinical significance
• Secondary deviation is always greater than primary deviation in
a recent onset paralytic squint
• Applies for vergence (yoke muscles)

14. Sherrington’s Law of Reciprocal Innervation
– During eye movement, an increase flow of innervation to
the contracting agonist muscle is accompanied by an equal
and simultaneous decreased flow of innervation to the
relaxing antagonist muscle.
– E.g. in Laevoversion - increased Innervational flow to the
LLR and RMR is accompanied by a decrease flow to the LMR
& RLR

15. Retinomotor value
The amount of ocular deviation required to maintain image at
fovea.
Once the image is on the fovea there is no incentive for the
ocular rotation

16. Retinomotor value is ______ at fovea
a. Maximum
b. Zero
c. half of the peripheral value
d. Varies with the size of image
It increases from center
to periphery.

17. Panums fusional area
a. Is wider in the periphery
b. Is thinner in the periphery
c. Represents where physiological diplopia is appreciated is
where corresponding points are stimulated
d. Represents where diplopia is appreciated

18. The horopter can be defined as the locus of all
points, which have ___________ disparity
a. Minimal
b. Zero
c. Maximum
d. Temporal
e. Nasal

19. The following statement is false about horopter
a. All object points lying on the horopter curve stimulate
corresponding retinal elements.
b. The diplopia elicited by object points off the horopter is
called physiologic diplopia.
c. The size of horopter is same for everyone
d. the distribution of the elements that correspond to each
other is not the same in the nasal and temporal parts of the
two retinas
The characteristics of the
horopter for each individual
vary within certain limits; each
person has his personal
horopter.

20. Which of the following statements is INCORRECT
a. Nasal retinal elements have a visual projection temporally
b. b. Disparate points refers to non-corresponding retinal
elements
c. A temporal retinal element corresponds to a temporal
retinal element in the other eye
d. A nasal retinal element corresponds to a temporal retinal
element in the other eye

21. What type of diplopia is associated with Sixth
nerve palsy
a. Crossed diplopia
b. Uncrossed diplopia
c. Vertical diplopia
d. Horizontal diplopia

22. BSV and fusion cannot occur if:
a. There is an overlap of visual fields
b. If the pupil pathway is damaged
c. Corresponding retinal points are stimulated
d. There is motor control of the visual axes
e. Significant pathology affects the vision and of the affected eye

23. Obstacles to fusion include significant
differences in image
a. Size
b. Colour
c. Contrast
d. Brightness
e. Size, colour, contrast & brightness

24. Temporal disparity gives the impression of:
a. Nearness
b. Farness
c. Smallness

25. Stereopsis is all of the following except
a. Occurs when images fall on the horopter
b. The ability of the visual system to appreciate depth
c. Achieved through the fusion of disparate images
d. Clinically expressed in terms of stereoacuity
e. A binocular phenomenon

26. Which of the following contributes to depth
perception
a. Experience
b. Motion parallax
c. Intensity of colours
d. Size of object
e. Experience, motion parallax, intensity of colours & size of object

27. When using stereograms with the eyes in the
crossed position, the stereogram stimulates:
a. Bitemporal or binasal dependent on various patient factors
b. Abnormal retinal correspondence
c. Bitemporal retina
d. Binasal retina
e. Nasal retina of one eye and temporal retinal of the other

28. Which one is wrong about stereopsis
a. disparate retinal elements should be stimulated simultaneously
b. the fused image should lie within Panum’s area
c. Vertical displacement produces no stereoscopic effect
d. The greater the horizontal disparity, the lesser the depth effect
Stereoacuity values are lowest at the point of fixation.
Targets that are in the periphery show higher thresholds.

29. What is the smallest amount of detectable
disparity ?
a. 2 sec of arc
b. 3 sec of arc
c. 4 sec of arc
d. 5 sec of arc
How much depth is 3 arc sec? It depends
on viewing distance ?
Converged at 6 meters, 3 arc sec = 1 cm =
Thickness of a finger
Converged at 0.6 meters (arms length) 3
arc sec = 0.1 millimeters – Ridges in your
fingerprint

30. Types of stereopsis
• Coarse stereopsis (also called gross stereopsis) appears to be used to
judge stereoscopic motion in the periphery. It provides the sense of
being immersed in one's surroundings and is therefore sometimes
also referred to as qualitative stereopsis. Coarse stereopsis is
important for orientation in space while moving, for example when
descending a flight of stairs.
• Fine stereopsis is mainly based on static differences. It allows the
individual to determine the depth of objects in the central visual area
(Panum’s fusional area) and is therefore also called quantitative
stereopsis. It is typically measured in random-dot tests; persons
having coarse but no fine stereopsis are often unable to perform on
random-dot tests, also due to visual crowding which is based on
interaction effects from adjacent visual contours. Fine stereopsis is
important for fine-motor tasks such as threading a needle

31. Stereo acuity measurement in children
• Lang test
• Frisby test
• Titmus fly test before 2 years of age
• Randot test and Random Dot stereo Test after 2 years of age