Suppression is a sensory adaptation mechanism of the visual system in which the brain actively inhibits or ignores visual input from one eye to avoid confusion or diplopia (double vision). It commonly occurs in conditions where normal binocular fusion is disrupted. Suppression is most frequently seen in strabismus, anisometropia, and amblyopia, particularly during early childhood when the visual system is still developing. The suppression may be unilateral or alternating, and can be central or peripheral, depending on the underlying condition and deviation.

1. SUPRESSION
PRESENTED BY:
SATYENDRA S SACHAN

2.  SUPPRESSION is the active but unconsious and
involuantary physiologic inhibitor of vision in one eye.
 An active phenomenon which may partly block or
eliminate the input to one eye.
 Suppression occurs at cortical level.

3. Diplopia
Patient fixates on the object with the fovea of one eye and the peri-
foveal retina of the deviated eye and observes double image.
Confusion
When dissimilar contours are presented to corresponding retinal area,
fusion becomes impossible instead the phenomenon of retinal rivalry
may be observed.

4. Types of suppression
Physiological suppression
Pathological suppression
(A) Facultative suppression
(B) Obligatory suppression

5. Physiological Suppression
 Refers to the suppression present in everyday life of
every individual having normal BSV
 Occurs due to the retinal rivalry & to avoid
physiological diplopia.
 Blurred images are suppressed when concentrating on
an object.
 Eg : While using monocular microscopes,
Watch makers and even while retinoscopy and
direct ophthalmoscopy.

6. Pathological Suppression
 It is present in manifest squint which is more than 10
degrees.
TYPES :
 FACULTATIVE SUPPRESSION.
 OBLIGATORY SUPPRESSION.

7. Facultative Suppression
 Facultative suppression is the suppression of the image
from one eye as needed for ocular comfort. It occurs
under certain conditions but ceases when the fixating
or dominant eye is covered.
 Deviated eye takes the fixation while covering the
good eye.
 Usually found where there is unequal retinal image size
and strabismus.

8. Obligatory Suppression
 Obligatory suppression is a constant suppression of the
image of one eye.
 It occurs under all conditions and remains when the
fixating or the dominant eye is covered.
 There is no sensory stimulus to the deviated eye.

9. Suppression Scotoma
- AREA OF SUPPRESSION
 Both H-prisms and V-prisms should be used.
 Can be done for near as well as distance.
 For distance
Target is 6/60 letter
 Keep the prisms in front of deviated or fixating eye.
 Increase the prism power till the patient appreciates
double.
 This occur due to image forming out of the suppression
area.

10.  When using BI prism ,we are measuring outer border of scotoma.
 BO prism is used to measure the inner border of scotoma.
 Then the prism calculation should be done as follows: e.g.:
14 BO + 8 BI = 6 BO.
 This 6 BO is area of suppression.
 The same procedure is applied to calculate the suppression area in
vertical direction.

11. - DEPTH OF SUPPRESSION
 Depth of suppression is measured with the help of an instrument
called Sbiza Bar.
 It is kept in front either of the eye.
 Can be done for near as well as distance.
 For distance target is 6/60 letter.
 Sbiza bar is placed in front of the eye and gradually it is shifted from
low to high density.
 If the patient reports diplopia before the half shifting of the bar
indicates lesser density suppression and after the half indicates higher
density suppression.

12. Investigations
 History.
To know the causes.
- Birth history.
Type of delivery (Forceps or normal delivery).
Type of birth (Premature or mature).
- Ocular history.
Any trauma .
Any infection.
- Systemic history.
- Family history

13. Cont…
 Visual acuity
Aided and unaided for both for distance and near.
 Refraction
Objective (cycloplegic) and Subjective .

14.  Binocular assessment
- Hirschberg corneal reflex test.
- Cover test (for distance and near)
Direct
Alternate
Cover uncover
- PBCT.

15. - Grades of BSV
1.Simultaneous Macular Perception.
2.Fusion.
3.Stereopsis.
- Accommodation
NPA
AOA

16. - Convergence .
NPC
Positive Fusional vergence
Negative fusional vergence
- Versions
Saccades
Pursuits

17. Tests for diagnosing Suppression
 WFDT
 Red filter test
 Vertical prism red filter test
 4 BO prism test
 Bagolini striated glass test

18. Worth four dot test.
 Based on colour dissociation.
 Red-Green filters are used
 Red in front of RE and Green in front LE.
 Done for near and distance.
 There are 1 Red, 1 White and 2 Green discs.
 In case A patient with suppression reports for
-Two Red = LE Suppression.
-Three Green = RE Suppression.

20. Red filter test.
 Based on colour dissociation.
 Red filter in RE.
 Done for near and distance.
 Torch light is shown for near and muscle light is shown
for distance.
 Red light with yellow border = BSV
 Only red light = LE suppression.
 Only yellow light=RE suppression.

21. 4 prism base out test.
 On placement of the prism over OD, levoversion
occurs during re-fixaton of OD, Indicating absence of
foveal suppression in OD.
 A subsequent slow fusional movement of OS is
observed to correct for the image displacement,
indicating absence of foveal suppression in OS.
 In another patient OS remains abducted 4 prism after
a prism is placed over OD. Absence of sensory fusion
movement of OS indicates the foveal suppression
scotoma of OS. The image has been shifted within a
non functioning retinal area . No stimulus exist for
refusion.

22.  To confirm this diagnosis the prism is placed over OS.
Neither eye will move under these circumstances,
since the prism has merely displaced the image within
the suppression scotoma and no stimulus exists for
refixation.

24. Bagolini glasses
 Based on form dissociation.
 The bagolini straited glass is placed at 135 degree in
RE and at 45 degree in the LE.
 A spot light is viewed through the glass produces
perpendicular images.

25. •The possible results could be:
•A = Normal.
•B = OD
Suppression.
•C = OD Micro-
suppression.
•D = Exotropia.

26. Treatment
GOALS
1. Eliminate the Suppression.
2. Stabilize sensory fusion.
3. Obtain pathological diplopia when strabismic.
4. Conversion of pathological into physiological
diplopia by elimination of strabismus.
5. Improve motor fusion skills.
6. Maintain BSV.

27. Exercises for suppression
-Patching
-Blinking
-Auto-flashing
-Bar reader
-Diploscope
-Cherioscope
-Remi-separator
-Bi-kinetic auto flashing

28. Patching
 Always prescribe with correction.
 Uniocular & Binocular.
 Patching can be given as direct or inverse.
 Direct for suppression.
- Direct patch can be given as total or partial
depending upon degree of suppression.
 Inverse patch for suppression with amblyopia.
 Suggested for 4-5 hours on daily basis for indoor work.

29.  Duration of patch is classified as
- Continuous : Throughout the day and night.
- Full time : Throughout waking hours.
- Part time : 4-5 hours in a day.

31. Blinking
 Helps as an exercise for suppression.
 It can be uniocular or binocular.
 Continuous blinking stimulates the suppression zone.
 It should be done for 5 min in a bright illumination.

32. Autoflashing
 Most effectively exercise undertaken on
Amblyoscope.
 Done with or without patching.
 Automatic flashing is done by manual control.
 The tubes are set to objective angle.
 First one light & then other is extinguished at an
interval of a few seconds.
 This induces alternation.
 The speed of alternation is slow first but gradually
increased.

33.  The target for this test depends upon the depth and
area of suppression scotoma.
 Solid target is placed in front of deviated eye and
hollow target in front of fixating eye.

34. Bar reader
 Based on the principle of physiological diplopia.
 It is placed at 30cm from the eye.
 The print size is N8.
 The patient is asked to hold the bar reader in such a way
that the letter should be visible.
 Suppression may be counteracted by using one of the following:
a. Allow the patient to use a close working distance
b. Tap or wiggle the bar reader
c. Rapidly cover and uncover the non-amblyopic eye
 This will the patient to appreciate physiological diplopia

36. Diploscope
 Depends upon physiological diplopia
 Binocular exercise with correction
 The normal patient see all three letter DOG
 If the patients has right eyes suppression he/she will see OG
 If left eye is suppressed then DO is seen.
 The aperture card distance is decreased.
 Then patients should report double letter or aperture.

37.  When appreciated double then the patient is asked to fuse it.
 After few months of exercise, BSV can be achieved.

39. BSV

40. RE Suppression

41. LE Suppression

42. Remi-separator
 Based on space dissociation
 Mostly used for horizontal deviation
 Opaque and transparent slides are used
 There is septum at middle for separating
 Normal patient appreciate both the image
 But the suppression patient will see either of the image
 Then will ask the patient to try to see the image
 Initially patient will report diplopia but after few
sessions of exercise BSV is achieved.

47. Cherioscope
 Based on space dissociation
 Two eyepiece having +8.00D lens (each)
 A mirror is placed diagonally from the middle of the
eyepiece to the base
 The patient is asked to see though the eyepiece,
keeping the good eye in mirrored septum
 And bad eye in non mirrored septum
 There is a image holder which carry image & its
reflection is seen in mirror

48.  The image is appreciated by good eye & it provides
stimulus to suppressed eye & the patient is asked to
draw the image.
 patient may draw the image in 1st
attempt but after
few exercise he/she can draw complete image.
 In this way BSV can be achieved.

50. Exercises for maintaining
BSV after elimination of
Suppression
 For conversion of pathological to physiological
diplopia.
- Brocks string.
- Stereogram cards.
- Aperture rule.
 For accommodation.
- RAF ruler.
- Pencil push up.
- Flippers.
- Hart chart.

51.  For vergence and versions.
- Vergence
Positive fusional vergence
1. Base out prism.
2. RAF ruler.
3. Pencil push up.
4. Brocks string.
5. Aperture rule (single slit)

52. Negative fusional vergence
1. Base in prisms.
2. Brocks string.
3. Aperture rule double slit.
-Versions
Saccades & pursuit.
4. SCCO
5. Pierce
6. King Devick
7. Marsden ball
8. DEM

53. References
 Clinical Orthoptics by Fiona Rowe.
 Practical Orthoptics in Treatment of Squint by Keith
Lee.
 Atlas of Strabismus by Gunter K. von Noorden, M.D .
 Clinical Management of Strabismus by Elizabeth.
 Classroom Notes.

54. THANK YOU