suppression

1. SUPPRESSION

2.  A sensory adaptation may be defined as the
manner in which a patient makes sensory
adjustments to an interruption in the normal
binocular single vision caused by the
occurrence of squint.
 There are three mechanism of sensory
adaptation.
1. Suppression
2. Amblyopia
3. Anomalous retinal correspondence

3.  It is defined as active central inhibition of
the desperate and the confusing image
originated from the deviated eye.

4.  Depending upon the etiopathogenesis
1. Physiological suppression
2. Pathological suppression (abnormal)
i) facultative
ii) obligatory
 Depending upon the retinal area where
image is suppressed.
1. Foveal suppression
2. Macular suppression
3. Peripheral suppression

5.  Depending upon the constancy
1. Intermittent
2. Constant
 Depending upon the eye involved
1. Monocular
2. Alternating

6.  It refers to suppression present in everyday
life of every individual having normal
binocular single vision.
 It occurs due to retinal rivalry and to avoid
physiological diplopia.
 For example – while using monocular
microscope ,monocular telescope.

7.  It refers to the suppression of the image of
one eye that occurs to avoid diplopia and/or
confusion.
 It occurs in patient with strabismus and
anisometropia.
1. Facultative – it occurs to avoid diplopia
and/confusion under conditions of binocular
vision bur ceases when the fixating or
dominant eye is covered
2. Obligatory – it refers to the constant
suppression of the image from one eye
which occurs under all conditions and
remains even when fixating or dominant eye
is covered.

8.  The extent of the area of the retina that
becomes suppressed and the time period
during which suppression occurs depends
upon the content of the visual field .
 Suppression does not occur over the whole
retina. It is restricted or localized to a
region around fovea of the deviating eye and
a peripheral region of the deviating eye on
which the fixation object is imaged.

9.  Usually the deviated eye has the regional
suppression i.e. horizontal oval area including
fovea and the peripheral area is suppressed.
 Some authors believe that patients with
exodeviation have hemi retinal suppression
rather than regional suppression.
 Suppression may occur in fixating eye.

10. 1. Worth four dot test
2. 4 D base out prism test
3. Diplopia test or red glass test
4. Bagolini striated glass test
5. Visual acuity test with project-O-chart slide
of American optical
6. Synoptophore test
7. After image testing

11. -To diagnose the suppression involving the peripheral retina.
-for this test red-green goggles are used. Red color in right
eye and green color in left eye.
-The patient having left suppression will see only two red
lights and that having right suppression will see only three
green lights.
- In the presence of alternate suppression patient will see
alternately two red lights and three green lights.

12.  This test is performed for detection of small angle
heterotropias and presence of central suppression
scotoma.
 To perform this test patient fixates a penlight than
a 4 D prism is placed with base out in front of the
right eye and the examiner observes the presence
of biphasic corrective movement of left eye.
 This is absent in presence of central suppression
scotoma.

13.  The prism displaces the image from the
fovea of right eye towards a point on a
temporal half of the retina.
 The relaxation movement of right eye will
elicit conjugate movement of both eye of
left side.
 If right eye has no Foveal suppression this
displaces the image in the left eye from the
fovea to temporal retina. Thus left eye will
make fusional movement in opposite
direction if no Foveal suppression is present.

14.  A pair of striated glasses are used in front of each
eye.
 A source of light is seen as a line at right angles to
striations.
1. Symmetrical cross response- in absence of manifest
squint ,indicates NRC and in presence of manifest
squint indicates ARC
2. Single line – it indicates suppression in other eye

15.  To measure the depth of suppression patient
is asked to fixate a small light and the red
ladder filter, in increasing density are placed
in front of the fixating eye till patient sees
double light.
 The greater number of layers needed the
deeper is suppression.

16. INDICATION
1. Patients with intermittent tropias
2. Patients with convergence insufficiency
3. Person with constant tropias
4. Person with fully corrected accommodative
esotropias
5. Post surgical patients with slight under
correction.

17. 1. Proper refractive correction
2. Occlusion therapy
3. Alignment of visual axes
4. Anti suppression orthoptic exercise
[A] Diplopia exercise
[B] exercise with use of red filter at near and
distance
[C] exercise using major ambloscope
[D] exercise with cheirscope
[E] exercise with Tibbs binocular trainer