Hess chart and it's Interpretation

Hess chart , its uses and interpretation.

1. Hess chart and it’s interpretation Azmat Khan Lecturer: The University Of Lahore Islamabad Campus

2. Walter Rudolf Hess (March 17, 1881 – August 12, 1973) Swiss physiologist Devised Hess chart in 1908 W on the  Nobel Prize in 1949 for mapping the areas of the brain involved in the control of internal organs.

3. Hess screens

4. Equipment

5. General Principle Principle is haploscopic. Chart is plotted based on the Herring's and Sherrington’s law of innervations. Dissociation of two eyes by means of colors.

6. Requirements Full understanding about what he is supposed to do, since the test is purely subjective. Good vision in both eyes. Foveal projection in the presence of normal retinal correspondence.

7. Patient must have NRC Little or no suppresion Color blind can’t appreciate red and green

8. Method Test is performed with each eye fixating in turn. It is done at 50 cm. 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.

9. 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 incomitance. Interpretation

10. Hess chart

11. Sequelae of extra ocular muscle palsies a. Overaction of the contralateral synergist b. Overaction of the ipsilateral antagonist c. Secondary underaction of the contralateral antagonist

12. Procedure Patient is seated 50 cm from the screen, holding a pointer projecting green light and wearing red and green goggles The screen has red lights in different positions of gaze, illuminated by the examiner, one at a time Patient is asked to superimpose each illuminated red light on the screen with the green light of his pointer

13. Procedure contd. The point where the patient projects the green light is recorded by the examiner on a paper chart which is a miniature copy of the screen After all the points are recorded, they are joined by straight lines The goggles are now reversed and the procedure repeated Each chart thus plotted belongs to the eye behind the green filter

14. Uses Assessment of incomitant strabismus Identification of the affected eye Identification of the underacting and overacting muscles Measurement of deviation (each small square=5 degrees) Differentiation between recent onset and long standing strabismus (development of muscle sequelae )

15. Uses contd Differentiation between mechanical and neurogenic strabismus (mechanical fields are compressed) Identification of A and V phenomenon Monitoring progress Selection of muscles for surgery Assessment of outcome of treatment Charting the field of binocular single vision

16. Interpretation Compare the two charts for: Size Position Shape

17. Size Determine which is the smaller field (belongs to the affected eye) Determine the underacting muscle/s (inward displacement of spots on the chart) Determine the overacting muscle/s (outward displacement of spots on the chart) Determine if the problem is recent or long standing Differentiate between mechanical and neurogenic pathology Look at the outer fields for minor problems which may not be noticeable in the inner fields

18. Position Determine the displacement of the central spot on the chart and measure it for hyper, hypo, exo or eso deviation (one small square=5 degrees)

19. Shape Sloping fields signify A and V phenomena

20. Examples of Hess charts that may be encountered in the examination Neurogenic causes Mechanical causes Third nerve palsy Orbital floor fracture Fourth nerve palsy Duane's syndrome Sixth nerve palsy Brown's syndrome Thyroid eye disease

21. Example What is the primary position of the affected eye?

22. Example What is the primary position of the affected eye? Ans. The right eye is hypo and exotropic .

23. Example contd. What is the diagnosis?

24. Example contd. What is the diagnosis? Ans. Right 3 rd nerve palsy.

25. Example What type of abnormality is seen in this patient?

26. Example What type of abnormality is seen in this patient? Ans. A mechanical one as the field of the affected left eye is compressed.

27. Example contd. In which direction is the affected eye likely to be restrited ?

28. Example contd. In which direction is the affected eye likely to be restrited ? Ans. Up and down gaze.

29. Example contd. What is the diagnosis?

30. Example contd. What is the diagnosis? Ans. Left orbital floor fracture.

31. Example Which is the abnormal eye?

32. Example Which is the abnormal eye? Ans. The right eye , as shown by the smaller field .

33. Example contd. Which muscle is underacting ?

34. Example contd. Which muscle is underacting ? Ans. The right lateral rectus.

35. Example contd. Which muscle is overacting?

36. Example contd. Which muscle is overacting? Ans. The left medial rectus.

37. Example contd. What is the diagnosis?

38. Example contd. What is the diagnosis? Ans. Right sixth nerve palsy.

39. Example Which is the abnormal eye?

40. Example Which is the abnormal eye? Ans. The left eye. (note the smaller field)

41. Example contd. Which muscle is underacting ?

42. Example contd. Which muscle is underacting ? Ans. The left superior oblique.

43. Example contd. Which muscle is overacting?

44. Example contd. Which muscle is overacting? Ans. The right inferior rectus.

45. Example contd. Is this a long-standing palsy?

46. Example contd. Is this a long-standing palsy? Ans. No, the muscle sequelae have not fully developed.

47. Example contd. What is the diagnosis?

48. Example contd. What is the diagnosis? Ans. Left superior oblique palsy.

49. Example Which muscle is underacting ?

50. Example Which muscle is underacting ? Ans. The right inferior oblique.

51. Example contd. Which muscle is overacting?

52. Example contd. Which muscle is overacting? Ans. The left superior rectus.

53. Example contd. What is the diagnosis?

54. Example contd. What is the diagnosis? Ans. Right Brown syndrome. The Hess chart is typical. The affected field is abnormal superiorly but normal inferiorly

55. Thankyou