The Hess screen test involves presenting lights in different positions of gaze on a screen and having the patient superimpose lights while viewing through colored lenses to dissociate the eyes. This allows evaluation of eye muscle function and detection of underaction or overaction. Key details include: - The Hess screen contains lights indicating positions of gaze and is viewed through red-green lenses to dissociate the eyes. - The procedure involves illuminating lights and having the patient superimpose them while viewing through the lenses. - Interpretation of the plotted results can detect muscle underaction or overaction, indicating conditions such as nerve palsies or restrictions in eye movement.

1. HESS SCREEN TEST :
PROCEDURE & INTERPRETATION
MEHEDI HASAN ., JUNIOR OPTOMETRIST ( IIEI&H )

2. WHAT IS A HESS SCREEN
The Hess screen test was designed by Walter Rudolf Hess in 1908 with subsequent
modifications.
The Hess screen contains a tangent pattern displayed on a dark grey background.
The Hess-Screen is a metal plate, 95 cm wide and 95 cm high. Includes 24 squares,
12 inner and 12 in outer field. Red lights that can be individually illuminated by a
control panel indicate the cardinal positions of gaze within a central field (15° from
primary position) and a peripheral field (30°); each square represents 5° of ocular
rotation

3. FIGURE : HESS SCREEN

4. PRINCIPLE
Principle is Haploscopic . Chart is plotted based on the Herring's and Sherrington’s
law of innervations. Dissociation of two eyes are made up by using red green
goggles . The Hess screen test can be described as a fovea-to-fovea (maculo-
macular) test. This occurs because two different colored test objects are used. Each
fixation target is red and the projected light is green. Wearing complementary red
and green filters means that neither eye can see the opposite test object.

5. 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 (NRA) .

6. PROCEDURE
• The test is done at 50 cm of distance.
• The eyes are dissociated by the use of
reversible goggles incorporating a red
and a green lens, the red lens in front
of the fixating eye and the green lens
the non-fixating eye.

7. • Red points of lights are illuminated at selected positions on the screen. The
patient holds a green pointer, and is asked to superimpose a green light over
each red light in turn.
• In orthophoria the two lights should be more or less superimposed in all
positions of gaze. The goggles are then reversed and the procedure repeated.
Software is available that facilitates the plotting of a Hess chart using a standard
desktop computer screen.

8. 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 incomitance.

9. USAGE OF HESS SCREEN
Diagnosis of :
• Under action or Over action of EOM.
• Mechanical or Neurogenic palsy.
• Congenital/Long standing or Acquired pals.
• A or V pattern
Planning of surgery and post-op effects of surgery.
Monitoring of condition.

10. SOME PLOTTED HESS CHARTS

11. Duane's retraction syndrome of type A more limited abduction than
Adduction.

12. Right 3rd nerve palsy.

13. Rt 6th nerve palsy

14. Lt Superior Oblique palsy

15. Rt Brown syndrome.

16. Thanks All.