Week 6 - Classification of Heterophoria and Heterotropua

Question 1

What causes heterophoria?

Answer 1

•most binocular anomalies result in the misalignment of the visual axes

• the fusion reflex maintains correct alignment of the two eyes

• if this fusion reflex is suspended the eyes will adopt the “ fusion free position and a measurable deviation of the visual axes will occur in

• the error of alignment that takes place when fusion is suspended is called heterophoria or phoria

Question 2

What is Orthophoria?

Answer 2

• if the eyes remain exactly parallel on dissociation for either near or distance fixation this is termed orthophoria ‘straight’

• in normals there is nearly always a slight tendency for the eyes to deviate slightly on dissociation

• the cover test will reveal this dissociation

Question 3

The cover test: Heterophoria

Answer 3

• this is performed to diagnose the presence of a heterophoria and heterotropia
• in heterophoria one eye is covered and that eye will deviate (i.e. under the cover)
• when the cover is removed the movement to regain fixation with that eye is seen
• the other eye will also make these movements on dissociation

Question 4

Deviation types Esophoria:

Answer 4

• convergence excess
deviation 10^ greater at near fixation

• divergence weakness
deviation 10^ greater at distance fixation

• non-specific
deviation similar at near and distance fixation

Question 5

Deviation types Exophoria:

Answer 5

• convergence weakness
Deviation 10^ greater at near fixation

• divergence excess
Deviation 10^ greater at distance fixation

• non-specific
deviation similar at near and distance fixation

Question 6

Vertical Heterophoria:

Answer 6

• the eye moves upwards under the cover and will then be seen to come down once the cover is removed hyperphoria

• the eye moves downwards under the cover and will then be seen to come up once the cover is removed hypophoria

• nomenclature of the deviation is determined by the high eye
- Right HYPERphoria = Left HYPOphoria =
R/L

Question 7

Cyclophoria: Rotations

Answer 7

• Excyclophoria:
upper poles of the corneas deviate outwards when fusion is prevented

• Incyclophoria:
upper poles of the corneas deviate inwards when fusion is prevented

Question 8

Types of heterophoria:

Answer 8

• Concomitant:-
- the dissociated deviation remains the same whichever eye is made to fixate
- no significant change in the 9 positions of gaze

• Incomitant:
- the dissociated deviation increases when one eve is made to fixate and decreases when the other eye fixates
OR
- it increases and decreases when the eyes are dissociated in different positions of gaze

Question 9

Aetiology of incomitant heterophoria

Answer 9

• Presence of paralytical or mechanical strabismus
• Diagnosed according to the underlying cause, e.g. esophoria in a 6th nerve palsy or hypophoria in Thyroid Eye Disease or hyperphoria in 4th nerve palsy
• Hyperphoria, hypophoria, cyclophoria are nearly almost always incomitant

Question 10

Incomitance can be due to:

Answer 10

• Underaction of one or more of the extraocular muscles as a result of cranial nerve palsy or mechanical or myogenic factors

Uncorrected or undercorrected spherical anisometropia. This requires more accommodation and therefore more convergence when one eye fixates than when the other fixates. Accurate correction should result in concomitance being restored.

Question 11

With incomitant heterophoria, the dissociated deviation:

Answer 11

• Increases when paretic eye made to fixate (secondary deviation)
• Decreases when fellow eye fixates (primary deviation)
• Varies when dissociated in different positions of gaze

Question 12

Heterotropia (manifest squint)

Answer 12

• when both eyes are open one eye will fixate the target and the other will deviate

Question 13

Cover test for heterotropia:

Answer 13

• in heterotropia one eye is covered and the other eye is observed
• if the uncovered eye moves to take up fixation , a heterotropia or manifest deviation of that eye is present
• you can have a ESOtropia, EXOtropia, HYPERtropia, HYPOtropia
• horizontal and vertical squints can co-exsist
• a heterotropia can be in one eye or both (alternating) although not at the same time

Question 14

Vertical heterotropia:

Answer 14

• if the uncovered eye moves downwards to take up fixation a hypertropia is present
• if the uncovered eye moves upwards to take up fixation a hypotropia is present
• nomenclature of the deviation is determined by which eye shows the manifest deviation
i.e. if the Px shows a manifest R Elevation on cover test we would refer to this as Right Hypertropia as they are not fixing with the right eye

Question 15

Heterotropia types:

Answer 15

• Concomitant
- ocular movement is within normal limits at time of onset of strabismus
- angle of deviation is virtually the same whichever eye is used for fixation in the primary position

• Incomitant
- occurs when there is limitation of ocular movement
- the angle of deviation increases as the eyes are turned in the direction of limitation and decreases when turned in opposite direction, with the exception of mechanical palsies where movement may be limited in opposing direction
- secondary deviation exceeds the primary deviation. The element of secondary comitance in long-standing cases can result in rality.

Question 16

Esotropia: Types

Answer 16

• One or other eye deviates nasally.

Primary
• Constant
- Accommodative Element (larger Near)
- Non-Accommodative
- Infantile
- Acquired
- Rare types (nystagmus block)

• Intermittent
- Accommodative
- Fully accommodative (control with gls)
- Convergence excess (controlled in distance only with glasses)
- Non-accommodative (rare)
- Near Esotropia (not affected by glasses)
- Distance Esotropia
- Cyclic Esotropia

Secondary ( due to loss or impairment of VA, usually in childhood)

Consecutive (previously exo)

Question 17

Primary Esotropia: Constant

Answer 17

The convergent deviation constitutes the initial defect

Constant:
- The esotropia is present under all conditions:-
• With an accommodative element: the deviation increases when accommodation is exerted i.e. when hypermetropic correction is removed
• Without an accommodative element: the deviation is unaffected by state of accommodation ie no hypermetropia

Question 18

Infantile esotropia:

Answer 18

• Onset < 6/12
• Large up to 45^
• Constant angle of deviation
• Cross fixates
• Usually alternating
• Not Accommodative
• Associated with Dissociated Vertical Divergence (DVD) and nystagmus that develops 12-18mths

Question 19

Primary Esotropia: Intermittent

Answer 19

Intermittent:
The esotropia is only present under certain conditions. These patients have Normal Retinal Correspondence (NRC)
• Accommodative Esotropia:
- In accommodative squint, the state of the convergent deviation is affected by the state of accommodation, and this is the primary factor in the aetiology of the squint i.e. Hypermetropia or high AC/A

Question 20

Fully Accommodative esotropia:

Answer 20

FULLY ACCOMMODATIVE ESOTROPIA: - normal binocular vision present for all distances when hypermetropia is corrected

Question 21

Convergence excess esotropia:

Answer 21

CONVERGENCE EXCESS ESOTROPIA: normal binocular vision for distance fixation, Esotropia on accommodation for near fixation

Question 22

Cover test findings for Fully accommodative esotropia: Example

Answer 22

• Hypermetropia
• CT cgls N sl esophoria with gd
rec
- D min esophoria with gd rec
- sgls N mod L Esotropia
- D sm LEsotropia

Question 23

Cover test findings for Convergence excess esotropia: Example

Answer 23

• Low/No Hypermetropia
• CT N Mod L Esotropia
D si esophoria with gd rec

High AC/A ratio
Bifocal - N sm esophoria with gd rec

Question 24

Fixation distance: Near vs distance esotropia

Answer 24

• NEAR ESOTROPIA:- Normal binocular vision for distance fixation, esotropia on near fixation even if the accommodative effort is relieved. (Normal AC/A ratio)

• DISTANCE ESOTROPIA:-
Esotropia on distance fixation, binocular single vision on near fixation (ensure full abduction)

Question 25

Cyclic Esotropia:

Answer 25

• CYCLIC ESOTROPIA: - every 24/48 hours
deviation occurs at regular intervals (child may be hyperactive).

• Non Specific
Intermittent esotropia not conforming to any pattern.

Question 26

Secondary and Consecutive esotropia:

Answer 26

• Secondary esotropia: Esotropia which occurs after pathological loss or impairment of

• Consecutive esotropia: Esotropia in a patient who has previously had Exotropia or exophoria
- Either spontaneous, with the passage of time or post-operative

Question 27

Classification of concomitant exotropia:

Answer 27

Primary
• Constant
~ Early onset
~ Decompensated intermittent
• Intermittent
~ Near exotropia
~ Distance exotropia
- True
- Stimulated (Controlled with accommodation or controlled with fusion)
~ Non-specific
Secondary (to loss Of VA)

Consecutive (previously eso)

Question 28

Primary exotropia: Constant

Answer 28

The divergent deviation constitutes the initial defect

• Constant:
- The Exotropia is present under all conditions.
- Early Onset: rare, suspect low VA
- Decompensated Intermittent: Often diagnosed from history / photographs; BSV may be recoverable (NRC)

Question 29

Primary Exotropia: Intermittent

Answer 29

The exotropia is only present under certain conditions.

• DISTANCE EXOTROPIA (divergence excess):
- Exotropia on distance fixation and binocular vision on near fixation
- Angle of deviation for near may or may not increase on
i) prolonged disruption of occlusion or
i) elimination of accommodation
- Cases which show increase for near are classified as ‘simulated’ and those who don’t as ‘true’

• NEAR EXOTROPIA :-
Normal binocular vision for distance fixation Exotropia on near fixation.
Would also have reduced convergence near point

• NON SPECIFIC EXOTROPIA:-
Exotropia, which shows intermittent binocular vision not conforming to any pattern.

Question 30

Secondary and Consecutive exotropia:

Answer 30

• Secondary exotropia
- Exotropia which occurs after pathological loss or impairment of vision

• Consecutive Exotropia
- Exotropia in a patient who has previously had esotropia or esophoria
Either spontaneous, with passage of time or post-operative

Question 31

Incomitant (Paralytic) Strabismus

Answer 31

• Occurs when there is limitation of ocular movement
• May be congenital or acquired
• May be horizontal, vertical and/or cyclical
• Classified according to the underlying cause of the limitation of movement:
- NEUROGENIC
- MECHANICAL
- MYOGENIC

Question 32

Pathological Binocular Diplopia

Answer 32

• initially the Px appreciates diplopia
• this results from the simultaneous appreciation of two separate images caused by the stimulation of non-corresponding points by the same object.
• the diplopia may be horizontal, vertical or torsional

Question 33

Homonymous (uncrossed) pathological diplopia

Answer 33

• binocular diplopia associated with esotropia, in which the image of the fixating object is received on the nasal retina of the deviating eye and is therefore projected temporally it results when non-corresponding retinal points are stimulated by the same object

Question 34

Heteronymous (Crossed) Pathological Diplopia

Answer 34

• binocular diplopia associated with exotropia, in which the image of the fixating object is received on the temporal retina of the deviating eye and is therefore projected nasally it results when non-corresponding retinal points are stimulated by the same object

Question 35

Confusion:

Answer 35

• is the simultaneous appreciation of two superimposed images due to the stimulation of corresponding retinal points by two different images

Question 36

Supression in cortical: mechanism

Answer 36

• At first when strabismus develops retinal correspondence is normal and suppression is absent, so that diplopia and confusion occur
• in young children diplopia and confusion are rapidly ignored
• this is termed suppression

• this suppression mechanism only occurs in children under the age of around 8 years
• when squints develop in older patients diplopia is a very troublesome symptom
• abnormal Retinal Correspondence describes a condition in which normally non-corresponding retinal areas of the two eyes co-operate to produce a form of binocular single vision