04/11/2023 1

MEASUREMENT OF HETEROPHORIA AND HETEROTROPIA

Presenter: Junu Shrestha2nd year B . Optom12th May 2013

Moderator: Gauri Sankar Shrestha

204/11/2023

Contents

Introduction Detection of phoria and tropia

Position of the globes Observation of head position

Determination of presence of deviation

Measurement of deviationObjective methodsSubjective methods

304/11/2023

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

404/11/2023

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.

504/11/2023

Compensating heterophoria

Is the condition where heterophoria is asymptomatic.

When fusional reserve is used to compensate for heterophoria. It is aka compensating vergence.

604/11/2023

Decompensating heterophoria

When heterophoria is not overcome by fusional vergence, signs and symptoms appear

It may lead to squint or stabismus

704/11/2023

B

Angle of heterophoria

Exophoria showing divergence or abduction behind the cover

804/11/2023

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.

904/11/2023

HETEROTROPIA

Is the manifest deviation in which fusional control is absent (motor fusion)

Aka squint or strabismus

1004/11/2023

Concomitant strabismus

The deviation does not vary in size with direction of gaze or fixating eye

Aka comitant strabismus

1104/11/2023

Noncomitant strabismus

The deviation varies in size with direction of gaze or fixating eye

Most incomitant strabismus is paralytic or restrictive

1204/11/2023

Heterotropia can be

HORIZONTAL- esotropia or exotropiaVERTICAL- hypertropia or hypotropiaTORSIONAL- incyclo or excyclodeviationCombined horizontal, vertical and/or

torsional

1304/11/2023

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 RE

1404/11/2023

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

1504/11/2023

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.

1604/11/2023

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

1704/11/2023

O

F

1804/11/2023

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.

1904/11/2023

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

2004/11/2023

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.

2104/11/2023

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

2204/11/2023

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

2304/11/2023

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

2404/11/2023

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.

2504/11/2023

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.

2604/11/2023

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

2704/11/2023

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.

2804/11/2023

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.

2904/11/2023

Factors to be specified during a cover testFactor 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 meters

3004/11/2023

Subjective Tests Diplopia test

Red Glass test Tangent screen Maddox Rod Maddox Wing Maddox double rod

testHaploscopic test

Lancaster R-G testVon Graefe method

Measurement of Deviation

Objective tests Prism and cover

testMajor AmblyoscopeCorneal reflection

tests Hirschberg Method Krimsky’s Method

Ophthalmoscopy and fundus photorgaphy

3104/11/2023

OBJECTIVE TESTS

3204/11/2023

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.

3304/11/2023

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.

3404/11/2023

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

3504/11/2023

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.

3604/11/2023

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)

3704/11/2023

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

3804/11/2023

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.

3904/11/2023

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

4004/11/2023

MEASUREMENT with the MAJOR AMBLYOSCOPE

Consists of 1. Chinrest2. Forehead rest3. Two tubes carrying targets seen

through an angled eye-piece one for each eye

4104/11/2023

SYNAPTOPHORE

4204/11/2023

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

4304/11/2023

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.

4404/11/2023

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.

4504/11/2023

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.

4604/11/2023

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.

4704/11/2023

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.

4804/11/2023

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 momentThe amount of deviation cannot be

determined by the prism and cover test or by any subjective tests.

4904/11/2023

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.

5004/11/2023

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.

5104/11/2023

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.

5204/11/2023

“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

5304/11/2023

5404/11/2023

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

5504/11/2023

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.

5604/11/2023

OPHTHALMOSCOPY and FUNDUS PHOTOGRAPHY

Fovea – 0.3 dd below a horizontal line extending through the geometric center of optic disc.

Excyclotropia

Incyclotropia

5704/11/2023

SUBJECTIVE TESTS Based on

Diploscopic principleHaploscopic principle

5804/11/2023

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.

5904/11/2023

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.

6004/11/2023

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.

6104/11/2023

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.

6204/11/2023

Red glass dissociate the light in addition to differentiate the two fields.

Dissociation is important in Hetrophoria Intermittent heterotropia

6304/11/2023

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.

6404/11/2023

6504/11/2023

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.

6604/11/2023

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.

6704/11/2023

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.

6804/11/2023

A streak image- oriented 90 from the axis of the cylinders

Performed with refractive correction .

6904/11/2023

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

7004/11/2023

The magnitude, hyper eye ,test distance, refractive correction and technique should be recorded for the vertical deviation

7104/11/2023

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

7204/11/2023

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

7304/11/2023

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

7404/11/2023

Maddox rod on RE Numbers on right sideIf light streak pass through no.

Uncrossed diplopia- esophoria through letters

Crossed diplopia- exophoria

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

7504/11/2023

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.

7604/11/2023

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

7704/11/2023

7804/11/2023

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.

7904/11/2023

MADDOX WING

8004/11/2023

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

8104/11/2023

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

8204/11/2023

8304/11/2023

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

8404/11/2023

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

8504/11/2023

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

8604/11/2023

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.

8704/11/2023

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.

8804/11/2023

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

8904/11/2023

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

9004/11/2023

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

9104/11/2023

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

9204/11/2023

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

9304/11/2023

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.

9404/11/2023

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.

9504/11/2023

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.

9604/11/2023

If the measuring prism is BD in LE, and if alignment obtained at

0 - orthophoria BD - left hyperphoria BU -Rt hyperphoria

9704/11/2023

References

1. Binocular vision and ocular motility- Gunrter K Von Noorden

2. Primary care optometry- Theodore Grossvenor

3. Clinical orthoptics-Fiona J. Rowe4. Clinical visual optics-Bennett & Rabbetts5. Internet

9804/11/2023

Thank you...