Heterophoria n tropia

MEASUREMENT OF
HETEROPHORIA AND
HETEROTROPIA
Presenter: Junu Shrestha
2nd year
B . Optom
12th May 2013
Moderator:
Gauri Sankar Shrestha
5/3/2014 1

Contents
 Introduction
 Detection of phoria and tropia
Position of the globes
Observation of head position
 Determination of presence of deviation
 Measurement of deviation
Objective methods
Subjective methods
5/3/2014 2

HETEROPHORIA
 Hetero- different
 Phoria – physiological position of rest
 Is the condition of eye in which the directions that
the eyes are pointing are not consistent with each
other
 Is a latent strabismus in which visual axes are
normally directed to the point of fixation but
deviate when the eyes are dissociated.
Introduction
5/3/2014 3

 The tendency of the lines of sight to deviate from the
relative positions necessary to maintain single binocular
vision for a given distance of fixation,
this tendency being identified by the occurrence of an
actual deviation in the absence of an adequate stimulus
to fusion and
occuring in variously designated forms according to the
relative direction or orientation of the deviation.
5/3/2014 4

Compensating heterophoria
 Is the condition where heterophoria is asymptomatic.
 When fusional reserve is used to compensate for
heterophoria. It is aka compensating vergence.
5/3/2014 5

Decompensating heterophoria
 When heterophoria is not overcome by fusional
vergence, signs and symptoms appear
 It may lead to squint or stabismus
5/3/2014 6

B
Angle of heterophoria
Exophoria showing divergence or abduction behind
the cover
5/3/2014 7

 If the visual axes are found to be parallel when the
patient views a distant object and all stimuli to
fusion have been eliminated, the condition is called
ORTHOPHORIA.
 if the visual axes converge toward one another –
ESOPHORIA.
 If the visual axes diverge away from one another –
EXOPHORIA.
 If one of the visual axis deviates above or below –
HYPERPHORIA.
5/3/2014 8

HETEROTROPIA
 Is the manifest deviation in which fusional control is
absent (motor fusion)
 Aka squint or strabismus
5/3/2014 9

Concomitant strabismus
 The deviation does not vary in size with direction of
gaze or fixating eye
 Aka comitant strabismus
5/3/2014 10

Noncomitant strabismus
 The deviation varies in size with direction of gaze or
fixating eye
 Most incomitant strabismus is paralytic or restrictive
5/3/2014 11

 Heterotropia can be
HORIZONTAL- esotropia or exotropia
VERTICAL- hypertropia or hypotropia
TORSIONAL- incyclo or excyclodeviation
Combined horizontal, vertical and/or torsional
5/3/2014 12

Angle of
Heterotropia
B
Left exotropia, showing adduction of the deviating left eye to take up
fixation and corresponding abduction of the right eye behind cover
LE RE5/3/2014 13

DETECTION OF PHORIA & TROPIA
 POSITION OF THE GLOBES
 Estimating the relative position of the eye is to have
the pt. fixate a penlight at near vision and then at
distance
 If reflected images from the 2 corneas appear
centered under both conditions – visual axes are
aligned
5/3/2014 14

 An angle kappa is formed by failure of the
pupillary and visual axes of the eye to coincide.
 Pupillary axis- line passing through the centre of the
apparent pupil perpendicular to the cornea.
 Visual axis – aka line of sight, connects the fovea
with the fixation point.
 Angle kappa is formed at the intersection of these
two axes at the center of the entrance pupil.
5/3/2014 15

 The pupillary axis touches the posterior pole of the
globe slightly nasal and inferior to the fovea
The corneal reflection of a penlight is not centered but lies
slightly nasal to the center positive angle kappa
If the fovea’s position is nasal to the point at which the
optical axis cuts the globe’s posterior pole, the corneal
reflection of a light will appear to lie on the temporal
side of the pupillary center negative angle kappa
5/3/2014 16

 In high myopia, peudoesotropia is seen due to nasal
displacement of the fovea.
 In Retinopathy of prematurity, the macula is pulled
in the temporal direction, resulting in positive angle
kappa aka pseudoexotropia.
5/3/2014 18

Size of angle Kappa
 Positive angle kappa ranges - 3.5° to 6.0°
average 5.082° in emmetropic eyes
 In hypermetropic eyes - 6.0° to 9.0°
average - 7.55°
 In myopic eyes – 2.0° may even be negative
Donders FC; On the anomalies of Accommodation and Refraction of the Eye
5/3/2014 19

Clinical significance
 Since angle may simulate , conceal or exaggerate a
deviation, the angle kappa must be considered to
obtain the best estimate of the actual deviation.
5/3/2014 20

Observation of head posture
 Pts with comitant horizontal heterotropias have
normal head position.
 In nystagmus, the frequency and amplitude may
reduce or dampens in certain direction where the
visual acuity is optimal. Head is turned to that
direction when looking straight ahead.
 Pt having high U/L amblyopia turn their head away
from amblyopic eye
5/3/2014 21

 Abnormal head positions in connection with
incomitant and paretic deviations are usually
assumed to obtain binocular co-operation or to
avoid diplopia.
 “The pt chooses the least inconvenient position of
the head by which the paretic muscle is sufficiently
relieved so that binocular single vision can be
obtained.”
-Bielschowsky
5/3/2014 22

Determination of presence of deviation
COVER TEST
 Differentiates
 orthotropia from an ocular deviation
 The deviation is latent or manifest
 The direction of deviation
 The fixation behaviour
 Whether visual acuity is significantly decreased in one
eye
5/3/2014 23

 A cover is placed briefly before the eye that appears to
fixate while the pt looks a small object, or a 6/9 VA
target
 Performed for distance and near.
 Covering one eye of a patient with normal binocular
vision interrupts fusion
 Eg. If a pt has heterotropia and the fixating eye is
covered, the opposite eye will move from heterotropic
position to take up fixation and the covered eye will
make a corresponding movement in accordance with
Hering’s law.
5/3/2014 24

 If there is no manifest deviation i.e. no movement of the
fellow eye when either eye is covered, a cover-uncover
test will determine the latent deviation.
 The covered eye is examined just after uncover.
 Eg. If a pt has heterophria, the covered eye will deviate
in the direction of the heterophoric position. When the
eye is uncovered , it will move in opposite direction to
reestablish binocular fixation.
5/3/2014 25

The possible results of the cover and cover-
uncover test are
 On covering the seemingly fixating eye:
 No movement of the other eye- there was binocular fixation
before cover
 Movement of redress of the other eye: a manifest deviation
was present before cover
5/3/2014 26

 On uncovering the eye:
 Movement of redress of the uncovered eye (fusional
movement), no movement of the other eye:
heterophoria is present
 No movement of either eye; uncovered eye deviated;
opposite eye continues to fixate: alternating
heterotropia is present
 Uncovered eye makes movement of redress and
assumes fixation with one eye; preference of fixation
with one eye: a U/L heterotropia is present.
5/3/2014 27

Modified Cover Test
 Introduced by Speilmann
 A translucent occluder is used.
 Covering both eyes with translucent occluders permits a
quick preliminary determination of whether an
esotropia is of refractive –accommodative or non-
accommodative origin.
5/3/2014 28

Factors to be specified during a cover test
Factor specified Choices
Type of deviation Phoria or Tropia
Frequency(if strabismic) Constant or Intermittent
Laterality(if constant
strabismic)
Unilateral or Alternating
Magnitude In prism diopters
Direction Eso, Exo, Hypo, Encyclo,
Excyclo or combination
Comitancy Comitant or Incomitant
Refractive correction In Diopters
Test distance In meters5/3/2014 29

Subjective Tests
Diplopia test
 Red Glass test
 Tangent screen
 Maddox Rod
 Maddox Wing
 Maddox double rod test
Haploscopic test
 Lancaster R-G test
Von Graefe method
Measurement of Deviation
Objective tests
Prism and cover test
Major Amblyoscope
Corneal reflection tests
 Hirschberg Method
 Krimsky’s Method
Ophthalmoscopy and
fundus photorgaphy
5/3/2014 30

PRISM and COVER TEST
 Principle: there will be no
movement of the eyes when
the selected prism causes
the image to fall on the fovea.
 A cover is placed alternating in front of each eye while
the pt maintains fixation. The eye that is uncovered
makes a movement of redress in the direction opposite
that of the deviation.
5/3/2014 32

 To measure esotropia, the prism must be placed
base out, for an exotropia – base in, for aright
hypertropia – base down in front of RE or base up
in front of LE.
 Reduces the movement of redress and the prism
strength is increased until the movement is offset.
 In pts with horizontal and vertical deviation, 1st the
horizontal deviation is neutralised with prism and
then to vertical deviation.
5/3/2014 33

Physiologic basis
 Redress in the prism and cover test is a psycooptical
reflex movement that occurs when the eye fixates.
 The sensory origin of this reflex movement is from
the stimulation of a peripheral retinal area in the
deviated eye by the fixation object.
 To place the fixated image on the fovea
5/3/2014 34

 Movement is quantitative and is directly
proportional to the distance of the fovea from the
stimulated peripheral retina.
 Placing prisms of increasing power in front of the
eyes brings the image of the fixated object closer to
the fovea, causing a corresponding decrease in
movement of redress.
5/3/2014 35

 Adequate fixation target and a technique that
ensures relaxed accommodation and maximum
dissociation is used.
 For distance fixation 6/9 VA symbol and a picture
target for near.
 At 6m the stimuli to accommodation and
convergence are assumed to be zero (although the
actual stimulus to accommodation is 0.17D and for
convergence is 1p.d.)at 40cm the stimulus to
accommodation is 2.50D to convergence is 15p.d.(for
IPD 64mm)
5/3/2014 36

Limitations of prism cover test
1. Presupposes accurate fixation and cannot be
performed if the deviating eye is blind or has
grossly eccentric fixation. In EF, the test provides
wrong measurements as the movement of redress
stops when the stimulus falls on the eccentric retinal
area not the fovea.
2. With loose prisms, when a low prism is added to a
high power prism, the arithmetic addition doesnot
give the resultant power
5/3/2014 37

3.The amount of deviation measured by an
ophthalmic lenses is variable depending on
position(how the prism is held). Eg a 40 glass
prism with a posterior face held in frontal position
gives only 32 of effect.
 Glass prisms are calibrated for use in the
prentice position, i.e. the posterior face of
the prism is perpendicular to the line of
sight of the deviating eye.
 Plastic prisms are calibrated for use in
the frontal plane position i.e. parallel
to the infraorbital rim.
5/3/2014 38

4.When measuring large angle horizontal deviation
with a prism bar, even slight oblique shifts of the bar
can include a vertical displacement of the image,
mimic a vertical deviation and cause vertical
diplopia
5.Spectacle lenses affects the measurement of
strabismic deviation. Plus lenses decrease and minus
lenses increase the measured deviation.
 Becomes clinically significant with powers of more than
5D
5/3/2014 39

MEASUREMENT with the MAJOR AMBLYOSCOPE
Consists of
1. Chinrest
2. Forehead rest
3. Two tubes carrying targets seen through an
angled eye-piece one for each eye
5/3/2014 40

 Tubes are placed horizontally and supported by a
column
 Distance between the tubes can be adjusted -
correspond accurately to the pt’s IPD.
 The axis of tube is in line with the center of rotation
of the eyes.
 Adjustments for vertical separation of targets and
cyclorotational adjustments
 Illumination system
 Increase or decrease stimulus luminance
5/3/2014 42

 Position of targets is fixed in focal plane of a +6.0D
or +6.5D lens so that they are at optical infinity
 To induce accommodation, auxilliary minus lenses
are placed in front of the eye pieces
 Deviation is measured by moving the arms of the
major amblyoscope into the position that images of
the target fall on the respective foveal areas.
5/3/2014 43

 The arms are moved until there is no further fixation
movement of the eyes in an alternate cover
test.(either by actual covering or by alternately
extinguishing the light on one side of the instrument)
 Horizontal deviations are compensated for by
moving the synaptophore arms, vertical deviations
by elevating or depressing the synaptophore
pictures.
5/3/2014 44

 When one eye is deeply amblyopic without the
capacity for fixation the angle can be determined
by shifting the synaptophore arm in front of the
amblyopic eye until the corneal reflex is centered in
the pupil
1.If corneal fixation is present, place one arm at zero
and the other at presumed angle of deviation.
Both pictures are illuminated. Pt fixates on center of
one picture.5/3/2014 45

This picture is shut off and the examiner observes
whether the other eye makes a fixation movement.
The arms are shifted until no fixation movement is
visible.
Between each phase, both pictures are illuminated so
that binocular vision is possible.
Aka monocular cover test or the simultaneous prism
cover test.
5/3/2014 46

2.Both pictures are shown alternately and the
synaptophore arms are adjusted until no refixation
movement develops.
Aka Alternate cover test and alternate prism cover
test since no binocular vision is possible.
5/3/2014 47

CORNEAL REFLECTION TESTS
 Estimation/ measurement of the deviation by
observing the first purkinje image
 Especially preferred when:
The deviated eye is blind or has low VA
In young children, unable to maintain fixation for
a longer than a moment
The amount of deviation cannot be determined
by the prism and cover test or by any subjective
tests.
5/3/2014 48

 Pt is instructed to watch a penlight held at 40cm by
the examiner
 Observes the corneal reflexes in the pts eye
 If no tropia exists, each corneal reflex will be located
approx 0.5mm nasal to the center of the pupil.
5/3/2014 49

 The corneal reflection is on the nasal side of the
deviated eye in exotropia, on the temporal side in
the esotropia, below the corneal center in
hypertropia and above it in hypotropia.
5/3/2014 50

Hirschberg Method
 When both eyes unoccluded and the pt still fixates
the penlight, the position of the corneal reflexes in
both eyes under binocular condition is noted and is
compared with the corresponding positions and with
the corresponding position under monocular
condition.
5/3/2014 51

 “Each 1mm of decentration of the corneal reflection
correspond to 7° of deviation of the visual axis.”
Hirschberg
 1mm displacement ~7 or 15
Brodie 1987
 1mm displacement~20-22
Hasebe at al 1998
5/3/2014 52

Krimsky’s method
 Prism is used to change the position of the corneal
reflection in the deviating eye.
 Amount of prism needed to reposition corneal
reflection in the deviating eye to the angle lambda
5/3/2014 54

 A penlight is held 50cm in
the midplane
 Prism bar is placed in front
of the fixating eye and is
increased until the corneal
reflection in the deviating
eye moves to angle lambda
position.5/3/2014 55

OPHTHALMOSCOPY and FUNDUS
PHOTOGRAPHY
 Fovea – 0.3 dd below a horizontal line extending
through the geometric center of optic disc.
Excyclotropia
Incyclotropia
5/3/2014 56

SUBJECTIVE TESTS
 Based on
Diploscopic principle
Haploscopic principle
5/3/2014 57

DIPLOPIA TEST
 Determination of the subjective localization of a
single object point imaged on the fovea of the
fixating eye and on extrafoveal retinal area in the
other eye
 In esotropia, where the image of the fixation point
in the deviated eye falls on a nasal area nasal to the
fovea, there should be uncrossed diplopia.
5/3/2014 58

 In exotropia, where the image of the fixation point
in the deviated eye falls on a retinal area temporal
to the fovea, there should be crossed diplopia.
 If retinal correspondence is normal, double images
not only should be properly oriented but also should
have a distance equal to the angle of squint.
5/3/2014 59

 The distance of the double images is then a measure
of the deviation; but with spontaneous diplopia, it is
difficult for the patient to state whether the images
are crossed or uncrossed.
 The two visual fields must be separated.
5/3/2014 60

Red glass test
 A red glass is placed in front of one eye.
 Pt fixates a small light source and states whether the
red light is to the right or to the left and above or
below the white light.
 If the white fixation light is in the center of the
maddox cross, pt must state the numbers near
which the red light is seen.
5/3/2014 61

 Red glass dissociate the light in addition to
differentiate the two fields.
 Dissociation is important in
 Hetrophoria
 Intermittent heterotropia
5/3/2014 62

 The red glass must be dark enough to make it
impossible for the pt to see anything but the red
fixation light to prevent fusional impulses from the
surrounding of the fixation light.
 Generally the filter is placed before the fixating eye,
which is less likely to suppress the darkened image
of fixation light.
5/3/2014 63

Tangent screen test
 Introduced by Freeman
 A green maddox rod is held before the pt’s right
eye while the left eye views a scale of red
transilluminated number.
 The white light at the center of the scale produces
the streak, while the red numbers and green
coloured rod eliminate the additional streaks thet
would otherwise have been caused if white number
had been used.
5/3/2014 65

 The scale calibrated in prism dioptres for the
assumed testing distance, is placed obliquely, and
hence may be used to measure both horizontal and
vertical deviations.
 Odd numbers are used on one side of the spot and
even numbers on the other.
5/3/2014 66

Maddox rod
 Consists of small glass rods(a series of planoconvex
cylinders in red or white) causes an astigmatic
elongation of the fixation light and may be placed
to produce a vertical or horizontal streak to
measure the horizontal and
vertical deviation.
5/3/2014 67

 A streak image- oriented 90 from the axis of the
cylinders
 Performed with refractive correction .
5/3/2014 68

Vertical rod to measure the vertical
deviation
 Maddox rod is oriented vertically infront of one eye
and a measuring prism in other
 Starting with 8 or 10 prism base up or base down
prism the amount of prism power is gradually
reduced until pt reports the horizontal streak goes
through the spot
5/3/2014 69

 The magnitude, hyper eye ,test distance, refractive
correction and technique should be recorded for the
vertical deviation
5/3/2014 70

Horizontal rod to measure lateral phoria
 Both methods for near and distance
 Stabilization of accommodation is not significant for
vertical deviations because fluctuation of deviations
affect only the horizontal angle
 Can be assessed by
 Thorington method
5/3/2014 71

 Uses horizontally oriented distance test chart having
a spot light in center and numbers or letters
extending on either side
 Horizontally oriented Maddox rod is placed in front
of one eye and the pt is asked to report the position
of the vertical streak, the number letter or through
the spot.
H G F E D C B A 0 1 2 3 4 5 6 7 8
5/3/2014 72

 Because each prism diopter of deviation at
6m results in a tangent distance of 6cm, to have 1
steps, the no. or letters must be placed 6cm apart
5/3/2014 73

 Maddox rod on RE
 Numbers on right side
If light streak pass through no.
Uncrossed diplopia- esophoria
through letters
Crossed diplopia- exophoria
5/3/2014 74
H G F E D C B A 0 1 2 4 5 6 7 8
H G F E D C B A 0 1 2 4 5 6 7 8

 Can also be used at 40cm
 At 40cm, each prism diopter of power is represented
by a deviation of 0.4cm.
 Can also be designed to measure the vertical phoria
by aligning the numbers and letters vertically above
and below the light source.
5/3/2014 75

 Since this method uses no. and letters, which exerts
some control over accommodation this test doesnot
present the problem of lack of control of
accommodation
5/3/2014 76

Maddox wing
 For amount of heterophoria in near fixation
 A vertical arrow is presented to one eye and a
horizontal tangent scale to the other to give the
measurement of the horizontal phoria .
 A horizontal arrow and vertical scale are used to
measure the vertical imbalance.
 Scales are mounted at the fixed viewing distance of
1/3m.
5/3/2014 78

Maddox double rod test
 Quantitative determination of cyclodeviation
 Red and white maddox rods are placed in the trial
frame. Red before RE and white before LE.
 Direction of glass rods is aligned with the 90° mark
of trial frame
5/3/2014 80

 A spot light is shown, for which the pt sees horizontal
streaks.
 A vertical prism may be added to separate the
images for easier identification.
 If one line appears slanted toward the nose,
excyclotropia of RE is present.
 Maddox rod is turned until the red line is seen parallel
with the white line. E.g. toward the 100° mark of the right
trial frame, 10° right exotropia is present
5/3/2014 81

Bagolini striated glasses
•Produce an image of a streak
of light, perpendicular to the
axis of striations when viewing
a spot light.
•Axes of striation at 90°
•If two lines fuse- no
cyclotropia
•If not the amount by which
the glasses are turned gives the
direction and amount of
cyclotropia
5/3/2014 83

HAPLOSCOPIC TESTS
 Two test objects rather than one are presented to
the patient
 assumption: NRC
 Visual field of two eyes are differentiated and
dissociated by presenting different target with major
abmlyoscope
 Each eye with different colour filter
 Polaroid projection
5/3/2014 84

Lancaster test / R-G test
 Uses a window shade type of screen (ruled into
squares of 7cm) so that at distance of 2m each
square subtends approx 2°
 Pt red green reversible googles
 2 projectors are used
 Red with examiner
 Green patient
 Image formed by projector are linear
5/3/2014 85

 In NRC the streaks will be separated objectively on
the screen by an amount corresponding to the
deviation of the visual axes.
 Since the projected image is a line, the pts response
may indicate the presence of cyclotropia when the
streak is tilted.
 Tilt of the retinal image is opposite to the tilt of the
horizontal line as seen by the observer.
5/3/2014 86

 When the line is seen slanted toward the nose, an
excyclodeviation is present.
 The line is always tilted in the direction in which the
offending muscle would rotate the eye if it were
acting alone.
5/3/2014 87

Von Graefe Method
 The method of phoria measurement in which a
dissociating prism is placed in front of one eye and a
measuring prism in front of the other eye.
 The dissociating prism should be strong enough to
cause diplopia
5/3/2014 88

 A base down prism is placed in front of one eye
causes the image on the retina to be displaced
downward, below the macular area, so the object
that formerly was seen straight ahead is then seen
as being displaced upward
5/3/2014 89

Measuring lateral phoria
 Target: vertical line of 20/20 letters
 A vertical prism of 7 or 8 is placed in front of one
eye
 A base in prism as the measuring prism in other eye
5/3/2014 90

 If BU in LE and BI in RE, lower image towards left is
seen by left eye and upper image towards right is
seen by right eye.
 At this point, two procedures can be used
 Alignment method
 Flash method
5/3/2014 91

Alignment method
 The strength of the BI prism is decreased until both
images are on same line.
 0 - orthophoric
 But if the measuring prism indicates BI prism at
alignment the pt is exophoric and if it indicates BO
the pt is esophoric
5/3/2014 92

Flash method
 The prism strength is decreased but the eye is
occluded in doing so.
 It prevents the continuous viewing of the charts
preventing the chance of fusion.
5/3/2014 93

Measuring vertical phoria
 When dissociating for the vertical phoria
measurement, base in prism is used.
 Eyes are able to make much larger fusional
convergence movements than fusional divergence
movements.
 15 BI in one eye and a measuring prism BU or BD
in other eye.
5/3/2014 94

 Target: a horizontal row of 20/20 letters on the
chart at 6m or 40cm.
 Pt is asked to report when the two rows of letters
are on the same level.
 Prism power is reduced until the patient reports
alignment.
5/3/2014 95

 If the measuring prism is BD in LE, and if alignment
obtained at
 0 - orthophoria
 BD - left hyperphoria
 BU -Rt hyperphoria
5/3/2014 96

References
1. Binocular vision and ocular motility- Gunrter K
Von Noorden
2. Primary care optometry- Theodore Grossvenor
3. Clinical orthoptics-Fiona J. Rowe
4. Clinical visual optics-Bennett & Rabbetts
5. Internet
5/3/2014 97

Heterophoria n tropia

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