BCSC Pediactrics (Strabismus Terminology) Flashcards
What Greek word is strabismus derived from and what does this mean?
Starbismos which means “to squint, to look obliquely or askance.”
Define strabismus.
Ocular misalignment (of any cause or type)
Define orthophoria. What term is used synonymously with orthophoria.
Orthophoria is the ideal condition of ocular alignment under binocular conditions.
Define heterophoria (or phoria).
Is an ocular deviation kept latent by the fusional mechanism.
Define heterotropia (or tropia).
Is an ocular deviation that is manifest and not kept under control by the fusional mechanism.
What is meant by the term latent strabismus?
Phoria
What is meant by the term manifest strabismus?
Tropia
Is orthophoria commonly seen in reality?
No. Most individuals have a slight exodeviation of both eyes which is overcome by fusional mechanisms. This exodeviation is therefore only evident during an EUA.
A esotropia or esophoria are both types of ________ strabismus? Why?
convergent strabismus. Because the visual axes converges at a point closer than the fixation target.
A exotropia or exophoria are both types of ________ strabismus? Why?
divergent strabismus. Because the visual axes converges at a point farther than the fixation target.
A hypertropia or hyperphoria are both types of ________ strabismus? In which direction (superiorly or inferiorly) is the cornea rotated? In which direction (superiorly or inferiorly) is the fovea rotated?
vertical strabismus. The cornea rotated superiorly while the fovea rotates inferiorly
A hypotropia or hypophoria are both types of ________ strabismus? In which direction (superiorly or inferiorly) is the cornea rotated? In which direction (superiorly or inferiorly) is the fovea rotated?
vertical strabismus. The cornea rotated inferiorly while the fovea rotates superiorly
Incyclotropia or incyclophoria are also known as ____ strabismus?
Intorsional
Excyclotropia or excyclophoria are also known as ____ strabismus?
Extorsional
Is fusional control always present in a phoria?
Yes. Any ocular deviation is corrected by the fusional mechanism (to prevent diplopia). If fusional control was temporally lost it would become an intermittent tropia.
Define a intermittent tropia.
A ocular deviation in which fusional control is present part of the time. Therefore, the eyes are only aligned some of the time under binocular conditions.
Define tropia.
A ocular deviation in which fusional control is not present. Therefore, the eyes are not aligned under binocular conditions.
Define a comitant (concomitant) strabismus.
The size of the ocular deviation does not vary by more than seven prism diopters with direction of gaze or with the eye used for fixating.
Define a incomitant (noncomitant) strabismus.
The size of the ocular deviation varies by more than seven prism diopters with direction of gaze or with the eye used for fixating.
A patient’s ocular deviation increases significantly when he alternates fixation between eyes. This is a form of _______ strabismus?
incomitant or noncomitant
A patient’s ocular deviation changes significantly with changes in his diretion of gaze. This is a form of _______ strabismus?
incomitant or noncomitant
A patient’s ocular deviation changes by a couple of prism diopters with changes in his diretion of gaze. This is a _______ strabismus?
comitant or concomitant
What are the two types of fixation? Define them.
Alternating fixation means there is spontaneous alternation of fixation from one eye to the other. Monocular fixation means there is a definite preference for fixation with one eye.
Define a congenital strabismus?
An ocular deviation present before 6 months, presumably related to a defect at birth.
Define a acquired strabismus?
An ocular deviation with onset later than 6 months, presumably with a period of apparently normal visual development.
What types of deviations are considered horizontal deviations?
Esodeviation or exodeviation
What types of deviations are considered vertical deviations?
Hyperdeviation or hypodeviation
What types of deviations are considered torsional deviations?
Incyclodeviation or excyclodeviation
Can a patient have multiple types of ocular deviation at one time?
Yes. This is referred to as combined deviation.
The abbreviations E, ET, and E(T) refer to what types of strabismus?
Esophoria, esotropia, and intermittent esotropia respectively.
The abbreviations X, XT, and X(T) refer to what types of strabismus?
Exophoria, exotropia, and intermittent exotropia respectively.
The abbreviations RH, RHT, and RH(T) refer to what types of strabismus?
Right hyperphoria, right hypertropia, and intermittent right hypertropia respectively.
The abbreviations LH, LHT, LH(T) refer to what types of strabismus?
Left hyperphoria, left hypertropia, and intermittent left hypertropia respectively.
The abbreviations RhoT and LhoT refer to what types of strabismus?
Right hypotropia and left hypotropia respectively.
The abbreviations O and Ex=O refer to what types of strabismus?
Orthophoria (orthotropia)
What is indicated by the addition of a (‘) to any of the strabismus abbreviations?
The strabismus is present at near (e.g. E(T)’ indicates a intermittent esotropia at near).
Is a strabismus always present at both near and distance.
No. This is why you must perform and document ocular alignment testing at both near and distance. Therefore, a normal exam at near and distance would be document: Ortho, Ortho’
What is the optical axis?
The line that best approximates the line passing through the optical center of the cornea, lens, and fovea.
What is the pupillary axis?
The imaginary line perpendicular to the corneal surface and passing through the midpoint of the entrance pupil.
What is the visual axis?
The imaginary line connecting the fixation point and the fovea.
Does the textbook definition of an optical axis exist in the eye? Why or why not?
No. The textbook optical axis does not exist in the eye because the lens is slightly decentered with respect to the cornea and the visual axis. Therefore, the best approximation of this line is taken to be the optical axis.
