The document details the principles of muscle movements in neuro-ophthalmology, explaining concepts such as synergists, antagonists, and yoke muscles. It outlines the construction and methodology of the Hess chart used for assessing ocular motility, highlighting the subjective evaluation of muscle action using colored glasses. Additionally, it describes how to interpret the results of the Hess chart, indicating underaction or overaction of specific eye muscles related to various ocular conditions.

1. HESS CHARTING
NEURO OPHTHALMOLOGY
1

2. EOM and their Movements
2

3. EOM and their Movements
3

4.  1. Synergists. It refers to the muscles having the
same primary action in the same eye; e.g., superior
rectus and inferior oblique of the same eye act as
synergistic elevators.
 2.Antagonists. These are the muscles having
opposite actions in the same eye. For example,
medial and lateral recti, superior and inferior recti and
superior and inferior obliques are antagonists to each
other in the same eye.
 3. Yoke muscles (contralateral synergists). It
refers to the pair of muscles (one from each eye)
which contract simultaneously during version
movements. For example, right lateral rectus and left
medial rectus act as yoke muscles for dextroversion
movements. Other pairs of yoke muscles are: right
MR and left LR, right LR and left MR
4

5.  Hering’s law of equal innervation. According
to it an equal and simultaneous innervation flows
from the brain to a pair of muscles which contract
simultaneously (yoke muscles) in different
binocular Movements
 Sherrington’s law of reciprocal innervation.
According to it, during ocular motility increased
flow of innervation to the contracting muscle is
accompanied by decreased flow of innervation to
the relaxing antagonist muscle. For example,
during dextroversion, an increased innervation
flow to the right LR and left MR is accompanied by
decreased flow to the right MR and left LR
muscles.
5

6. Basic concepts
 Agonist
 Antagonist
 Synergist
 Yoke muscle
Herring’s Law
Sherrington’s law
6

7. Hess chart construction
 To perform this test, a black cloth 3 ft wide
by 31⁄2 ft long, marked out by a series of red
lines subtending between them an angle of
5°, is used.
 At the zero point of this coordinate system
and at each of the points of intersection of
the 15° and 30° lines with one another and
with corresponding vertical and horizontal
lines, there is a red dot.
 These dots form an inner square of 8 dots
and an outer square of 16 dots.
7

8. HESS CHART
CONSTRUCTION8

9.  An indicator is provided consisting of three
short green cords knotted to form the letter Y.
 The end of the vertical green cord is fastened
to a movable black rod 50 cm long.
 The ends of the other two cords are kept taut
by black threads that pass through loops at
upper corners of screen to small weights at
corresponding upper corners of the screen.
 This arrangement enables the patient to move
the indicator freely and smoothly over the
whole surface of the screen in all directions.
9

10. HESS CHART
CONSTRUCTION10

11. HESS CHART
CONSTRUCTION11

12. HESS CHART
CONSTRUCTION12

13. PRINCIPLE
 Subjective assessment of deviation
Haploscopic priciple
13

14. PRINCIPLE
 Subjective assessment of deviation
 Diplopia principle: One target,
dissociation achieved with different colour
glasses
 Haploscopic principle: Two target, one
target pointed and patient has to
superimpose it with other
14

15. PREREQUISITES
 Patient should have the following:
 Full understanding about what he is
supposed to do, since the test is purely
subjective.
 Good vision in both eyes.
 Central fixation.
 Normal retinal correspondence.
15

16. METHOD
16

17. METHOD
17

18. Method
 Test is performed with each eye fixating in
turn.
 It is done at 50 cms.
 Patient wears red and green glasses.
 Eye to be tested should have green glass in
front of it.
 The chart has electronically operated board
with small red lights.
 Patient is asked to place green light in each of
points on red light as illuminated.
 Next the goggles are changed.
18

19. Interpretation
 Compression of space between the two plotted
fixation points indicates underaction of a muscle
acting in that direction.
 Expansion indicates overaction.
 Smaller field belongs to eye with paretic muscle.
 Unaffected eye shows larger field expressing the
overaction of the contralateral synergist.
 Fields of similar shape and size seen in comitant
deviation, while dissimilar shape and size indicate
19

20. INTERPRETATION OF HESS
CHART
 RIGHT LATERAL RECTUS
PALSY
20

21.  RIGHT LATERAL RECTUS
UNDERACTION: Rt
LR
OVERACTION: Lt
MR
21

22. HESS CHART
 LEFT LATERAL RECTUS
 OVERACTION: Rt
MR
 UNDERACTION: Lt
LR
22

23. HESS CHART
 LEFT SUPERIOR OBLIQUE
 OVERACTION: Rt IR UNDERACTION: Lt
SO
23

24. HESS CHART
 RIGHT INFERIOR OBLIQUE
 UNDERACTION: Rt
IO
 OVERACTION: Lt
SR
24

25. HESS CHART THIRD NERVE
PALSY25

26. HESS CHART FOURTH NERVE
PALSY
26

27. HESS CHART SIXTH NERVE
PALSY27

28. 28