22 Questions
What is the term for the error of alignment that occurs when fusion is suspended?
Heterophoria
In normal individuals, the eyes always remain exactly parallel on dissociation.
False
What is the purpose of the cover test?
To diagnose the presence of a heterophoria and heterotropia
Distance fixation represents the error between the position of the eyes produced by tonic convergence and _______________________.
parallelism
What is the movement seen in esophoria during the alternate cover test?
The eye moves inward under the cover
Match the following terms with their definitions:
Phoria = A measure of the error between the desired alignment of the eyes Tropia = A manifest deviation of the visual axes Heterophoria = A latent deviation of the visual axes Orthophoria = A condition where the eyes remain exactly parallel on dissociation
Heterophoria is a manifest deviation of the visual axes.
False
What is the term for the reflex that maintains the correct alignment of the two eyes?
Fusion reflex
What is the direction of movement of the uncovered eye in Hypertropia?
Downwards to fixate
Incomitant Heterotropia is also known as non-paralytic strabismus.
False
What is the term for the upper poles of the cornea deviating outwards?
Exyclotropia
In Cyclotropia, Incyclotropia is characterized by the upper poles of the cornea deviating _____________.
inwards
Match the type of Esotropia with its characteristic.
Primary Esotropia = Constant Esotropia Onset in infancy = Deviation increases with accommodation
What happens to the secondary deviation in long-standing cases of Incomitant Heterotropia?
It equals the primary deviation
What is the direction of the eye's movement in exophoria during the alternate cover test?
Outwards
Esophoria is a type of heterophoria characterized by convergence excess.
True
What is the difference between hyperphoria and hypophoria?
Hyperphoria is when the eye moves upwards under the cover, while hypophoria is when the eye moves downwards under the cover.
Incomitant heterophoria is often seen in the presence of _______________________ or mechanical strabismus.
paralytic
Match the following types of heterophoria with their characteristics:
Esophoria = Convergence excess Exophoria = Convergence weakness Hyperphoria = Eye moves upwards under the cover Hypophoria = Eye moves downwards under the cover
Heterotropia can be present in both eyes at the same time.
False
What is the sequence of events in the cover test for heterotropia?
Cover one eye, observe the other eye, and then remove the cover
What is the term for the deviation that increases when the paretic eye is made to fixate and decreases when the fellow eye fixates?
Incomitant heterophoria
Study Notes
Heterophoria (Latent Squint)
- Most binocular anomalies result in misalignment of the visual axes
- Fusion reflex maintains correct alignment of the two eyes
- Heterophoria is the error of alignment that takes place when fusion is suspended
- Phoria represents the error between the desired alignment of the eyes and the position produced by tonic, accommodative, and proximal convergence
Types of Phoria
- Esophoria:
- Convergence excess – deviation greater at near fixation
- Divergence weakness – deviation greater at distance fixation
- Non-specific – deviation similar at near and distance fixation
- Exophoria:
- Convergence weakness – deviation greater at near fixation
- Divergence excess – deviation greater at distance fixation
- Non-specific – deviation similar at near and distance fixation
Vertical Heterophoria
- Hyperphoria: the eye moves upwards under the cover and will then be seen to come down once the cover is removed
- Hypophoria: the eye moves downwards under the cover and will then be seen to come up once the cover is removed
- Nomenclature is determined by the high eye
Incomitant Heterophoria
- Dissociation deviation increases when one eye is made to fixate and decreases when the other eye fixates
- Or, it increases and decreases when the eyes fixate in different positions of gaze
- Aetiology: most are seen in the presence of paralytic or mechanical strabismus
- Diagnosed according to underlying cause, e.g., esophoria in 6th nerve palsy or hypophoria in TED or Hyperphoria in 4th nerve palsy
Heterotropia
- When both eyes are open, one eye will fixate the target and the other will deviate
- Cover Test (Cover – Uncover) is used to diagnose heterotropia
- Horizontal and vertical squints can coexist
- Can be in one eye or both (alternating) although not at the same time
Types of Heterotropia
- Esotropia:
- Eye is deviated inwards (convergent)
- Uncovered eye will move outwards (temporally) to take up fixation
- Exotropia:
- Eye is deviated outwards
- Uncovered eye will move inwards (nasally) to take up fixation
- Hypertropia:
- Eye is elevated upwards
- Uncovered eye moves downwards to fixate
Vertical Heterotropia
- Hypertropia: uncovered eye moves downwards to take up fixation
- Hypotropia: uncovered eye moves upwards to take up fixation
- Nomenclature is determined by the eye that shows manifest deviation
Cyclotropia
- Excyclotropia: upper poles of cornea deviate outwards
- Incyclotropia: upper poles of cornea deviate inwards
Learn about phoria, tropia, and heterophoria, including the misalignment of visual axes and the fusion reflex in binocular vision.
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