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AOC C.O. study materials
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AOC C.O. practice questions

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Question 1Orthoptic education and clinical/education competencies (standards set by the AOC)

Which professional body sets the entry-level education standards that orthoptic training programmes are expected to meet?

  1. The Accreditation Council for Graduate Medical Education
  2. The American Orthoptic Council Correct answer.
  3. The Joint Commission on Allied Health Personnel in Ophthalmology
  4. The American Academy of Ophthalmology

Explanation

The American Orthoptic Council (AOC) is the body responsible for orthoptic education standards, including curricula, examinations, and programme approval in the United States. Other organisations address different scopes such as ophthalmic technician certification or physician residency accreditation.

Question 2Orthoptic education and clinical/education competencies (standards set by the AOC)

In a patient with a comitant esotropia, which measurement technique is most appropriate for quantifying the deviation at both distance and near?

  1. Cover-uncover test alone
  2. Prism alternate cover test Correct answer.
  3. Hirschberg estimation only
  4. Worth 4-dot test

Explanation

The prism alternate cover test objectively neutralises the deviation and allows quantification in prism dioptres at both fixation distances. Cover-uncover merely detects the presence of a tropia, Hirschberg gives only a rough estimate, and the Worth 4-dot assesses fusion and suppression rather than measuring magnitude.

Question 3Orthoptic education and clinical/education competencies (standards set by the AOC)

Which test is designed primarily to assess the presence and grade of binocular single vision using polarised filters?

  1. Synoptophore after-image test
  2. Bagolini striated lenses
  3. Lang stereotest
  4. Titmus stereo test Correct answer.

Explanation

The Titmus test uses polarised vectograph targets viewed through polarising glasses to grade stereopsis. Bagolini lenses assess suppression and anomalous correspondence, the Lang test uses random-dot cylinder gratings without glasses, and after-image testing evaluates retinal correspondence rather than stereoacuity.

Question 4Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient reports diplopia that is worse on right gaze. Which finding best localises the problem to a right lateral rectus underaction?

  1. Reduced elevation of the right eye on upgaze
  2. Reduced depression of the right eye on downgaze
  3. Reduced adduction of the right eye on levoversion
  4. Reduced abduction of the right eye on dextroversion Correct answer.

Explanation

The right lateral rectus is the abducting muscle of the right eye, so its underaction produces limited abduction on right gaze (dextroversion). The other options describe actions of different muscles tested in different gaze directions.

Question 5Orthoptic education and clinical/education competencies (standards set by the AOC)

Which refractive error is most commonly associated with accommodative esotropia in young children?

  1. Low myopia
  2. High astigmatism
  3. Moderate to high hyperopia Correct answer.
  4. Anisometropia

Explanation

Uncorrected hyperopia demands excessive accommodation, which drives convergence and can precipitate accommodative esotropia. Myopia usually reduces accommodative demand, and astigmatism or anisometropia are not the classic trigger.

Question 6Orthoptic education and clinical/education competencies (standards set by the AOC)

What is the primary purpose of occlusion therapy in a child with amblyopia?

  1. To reduce the angle of strabismus
  2. To improve accommodation
  3. To eliminate suppression of the deviating eye
  4. To force use of the amblyopic eye Correct answer.

Explanation

Occluding the better eye forces fixation with the amblyopic eye, promoting recovery of visual acuity. It does not directly reduce the strabismus angle or accommodation, and suppression of the deviating eye is not the target.

Question 7Orthoptic education and clinical/education competencies (standards set by the AOC)

Which structure is primarily responsible for the near triad response during accommodation?

  1. Superior colliculus and pretectal area
  2. Trigeminal motor nucleus
  3. Abducens nucleus and lateral rectus
  4. Edinger-Westphal nucleus and ciliary ganglion pathway Correct answer.

Explanation

The near triad (accommodation, convergence, miosis) is mediated by parasympathetic fibres from the Edinger-Westphal nucleus via the ciliary ganglion. The abducens and trigeminal motor nuclei serve eye abduction and mastication respectively, and the pretectal area mediates the light reflex.

Question 8Orthoptic education and clinical/education competencies (standards set by the AOC)

Which of the following best describes the purpose of a synoptophore in orthoptic practice?

  1. To measure refractive error objectively
  2. To image the optic nerve head
  3. To record eye movements during reading only
  4. To assess and treat binocular sensory and motor anomalies using dissociated targets Correct answer.

Explanation

The synoptophore presents separate targets to each eye, allowing assessment of simultaneous perception, fusion, and stereopsis, and providing graded fusional exercises. It does not measure refraction, image the fundus, or record reading eye movements.

Question 9Orthoptic education and clinical/education competencies (standards set by the AOC)

A 6-year-old has a visual acuity of 6/6 in each eye but fails the 4-dot test at near with suppression of the left eye. Which condition does this most suggest?

  1. Convergence insufficiency
  2. Bilateral amblyopia
  3. Small-angle strabismus with suppression Correct answer.
  4. Normal binocular single vision

Explanation

The Worth 4-dot reveals suppression when one eye's dots are not reported, which occurs in strabismus with a suppression scotoma even when acuity is normal. Normal binocular vision would yield four dots, and convergence insufficiency does not produce suppression on this test.

Question 10Orthoptic education and clinical/education competencies (standards set by the AOC)

Which finding on the prism alternate cover test indicates an incomitant deviation?

  1. A consistent angle across all cardinal positions
  2. A latent deviation revealed only after dissociation
  3. A change in the measured angle with different gaze directions Correct answer.
  4. An equal angle at distance and near

Explanation

Incomitance is defined by a deviation that varies with direction of gaze, reflecting a muscle palsy or restriction. Equal angles across positions and distances indicate comitance, and a latent deviation is a separate phenomenon.

Question 11Orthoptic education and clinical/education competencies (standards set by the AOC)

During a cover test, the uncovered eye moves outward to take up fixation when the fellow eye is covered. This finding is consistent with which diagnosis?

  1. Exophoria
  2. Hypertropia
  3. Exotropia
  4. Esotropia Correct answer.

Explanation

When the fixating eye is covered, the esotropic eye must move outward (laterally) to take up fixation, revealing an inward deviation. An exotropia would require inward movement, and a hypertropia would require vertical movement.

Question 12Orthoptic education and clinical/education competencies (standards set by the AOC)

Which test is most appropriate for detecting anomalous retinal correspondence in a patient with a longstanding esotropia?

  1. Prism alternate cover test
  2. Hirschberg test
  3. Titmus stereoacuity test
  4. Bagolini striated lenses with a cover test Correct answer.

Explanation

Bagolini lenses allow evaluation of the sensory relationship between the eyes, and combining them with a cover test can reveal anomalous retinal correspondence. The prism cover test measures motor deviation, Hirschberg estimates angle, and Titmus measures stereoacuity, none of which directly diagnose ARC.

Question 13Orthoptic education and clinical/education competencies (standards set by the AOC)

A child with intermittent exotropia shows a well-controlled deviation at distance and orthophoria at near. Which management approach is generally appropriate initially?

  1. Observation with regular monitoring Correct answer.
  2. Immediate bilateral medial rectus recession
  3. Over-minus spectacle lenses for all activities
  4. Patching of the deviating eye

Explanation

Well-controlled intermittent exotropia with good near alignment often requires only observation, as many cases remain stable. Surgery is reserved for deterioration, and over-minus lenses are used selectively for near deviations rather than as a universal first step.

Question 14Orthoptic education and clinical/education competencies (standards set by the AOC)

Which clinical feature best distinguishes a comitant from a paralytic (incomitant) strabismus?

  1. Deviation magnitude varies with gaze direction in the incomitant type Correct answer.
  2. The comitant type is always associated with diplopia
  3. The incomitant type shows equal angles in all positions
  4. Deviation is larger at near than distance in the comitant type

Explanation

Incomitance is characterised by a deviation that changes with gaze direction, whereas comitant deviations are similar across positions. Distance-near differences and diplopia do not reliably separate the two categories.

Question 15Orthoptic education and clinical/education competencies (standards set by the AOC)

What is the primary rationale for prescribing glasses before considering surgery in a child with refractive accommodative esotropia?

  1. Glasses eliminate suppression scotomas
  2. Correcting hyperopia relaxes accommodation and reduces convergence Correct answer.
  3. Glasses permanently weaken the extraocular muscles
  4. Glasses improve stereopsis independent of alignment

Explanation

Correcting hyperopia reduces the accommodative demand and thereby the accommodative convergence that drives the esotropia. Glasses do not weaken muscles, and improvements in suppression and stereopsis follow alignment rather than occurring independently.

Question 16Orthoptic education and clinical/education competencies (standards set by the AOC)

Which statement best describes the role of the orthoptist in a multidisciplinary ophthalmology team?

  1. Prescribing systemic medication
  2. Performing intraocular surgery
  3. Interpreting fundus fluorescein angiography
  4. Assessing and managing binocular vision, motility, and amblyopia Correct answer.

Explanation

Orthoptists specialise in the assessment and non-surgical management of binocular vision disorders, ocular motility, and amblyopia. Surgery, systemic prescribing, and angiography interpretation fall outside their scope.

Question 17Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient with a left sixth nerve palsy is examined. Which finding is expected on attempted left gaze?

  1. The left eye is exotropic in primary position with no gaze-dependent change
  2. The left eye fails to adduct and the deviation is greater on right gaze
  3. The left eye shows normal abduction with an associated vertical deviation
  4. The left eye fails to abduct and the deviation is greater on left gaze Correct answer.

Explanation

A left abducens palsy impairs abduction of the left eye, and the esotropia increases when gazing toward the affected side. Adduction is mediated by the medial rectus, and a gaze-independent deviation would suggest comitance.

Question 18Orthoptic education and clinical/education competencies (standards set by the AOC)

Which sensory adaptation is most likely to develop in a child with an early-onset constant esotropia?

  1. Alternating hypertropia
  2. Suppression scotoma of the deviating eye Correct answer.
  3. Enhanced stereopsis
  4. Normal retinal correspondence with full fusion

Explanation

Early constant strabismus typically leads to a suppression scotoma in the deviating eye to avoid diplopia and confusion. Enhanced stereopsis and full normal fusion are incompatible with a constant deviation.

Question 19Orthoptic education and clinical/education competencies (standards set by the AOC)

Which refractive correction strategy is used to reduce accommodative convergence in a patient with a high accommodative convergence/accommodation ratio esotropia?

  1. Minus lenses for all distances
  2. Bifocal lenses with additional plus at near Correct answer.
  3. Prism base-out for all distances
  4. Reducing the distance plus power

Explanation

A high AC/A ratio produces excess convergence at near, so adding plus power at near via bifocals relaxes accommodation and reduces the near deviation. Minus lenses would increase accommodation, and base-out prisms would worsen the esodeviation.

Question 20Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient demonstrates a variable, intermittent exodeviation that is only present after prolonged dissociation. Which term best describes this?

  1. Exophoria Correct answer.
  2. Convergence excess
  3. Intermittent exotropia
  4. Constant exotropia

Explanation

A deviation that appears only after dissociation and is otherwise controlled is a phoria, in this case an exophoria. Intermittent and constant exotropia are manifest deviations, and convergence excess refers to a near esodeviation.

Question 21Orthoptic education and clinical/education competencies (standards set by the AOC)

Which factor most strongly predicts a good prognosis for amblyopia treatment in a school-aged child?

  1. Presence of a constant strabismus
  2. Higher hyperopic refractive error
  3. Younger age at initiation of therapy Correct answer.
  4. Longer duration of untreated amblyopia

Explanation

Younger age at the start of treatment is the strongest predictor of success because of greater neural plasticity. Constant strabismus, higher refractive error, and longer untreated duration are associated with poorer outcomes.

Question 22Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient with a long-standing unilateral superior oblique palsy adopts a compensatory head posture. Which posture is most likely?

  1. Chin elevation
  2. Head tilt toward the affected side
  3. Head turn toward the affected side
  4. Head tilt away from the affected side Correct answer.

Explanation

In superior oblique palsy, the vertical deviation is worst when the head is tilted toward the affected side, so patients tilt away to minimise the deviation and maintain fusion. Head turn and chin elevation address horizontal or other vertical incomitances rather than this pattern.

Question 23Orthoptic education and clinical/education competencies (standards set by the AOC)

Which principle underlies the use of prisms in the conservative management of a small comitant esotropia with diplopia?

  1. Vertical prisms eliminate horizontal suppression
  2. Base-in prisms shift the image to relieve diplopia
  3. Base-out prisms relieve convergence demand and reduce the deviation Correct answer.
  4. Prisms permanently correct the strabismus angle

Explanation

In esotropia with diplopia, base-out prisms can reduce the convergence demand and help maintain single vision by altering the motor response. Base-in prisms would worsen the esodeviation, and prisms do not permanently correct the angle.

Question 24Orthoptic education and clinical/education competencies (standards set by the AOC)

A researcher compares two occlusion regimens for amblyopia and randomises children to groups. Which design element most strengthens the causal inference of the trial?

  1. Retrospective chart review
  2. Random allocation with concealed sequence Correct answer.
  3. Single-group pre-post comparison
  4. Case series reporting

Explanation

Random allocation with allocation concealment minimises selection bias and supports causal inference about treatment effects. Retrospective reviews, single-group comparisons, and case series lack a controlled comparison and are prone to bias.

Question 25Orthoptic education and clinical/education competencies (standards set by the AOC)

Which outcome measure is most appropriate for evaluating the effectiveness of a fusional convergence exercise programme?

  1. Best-corrected visual acuity alone
  2. Corneal thickness
  3. Pupil diameter
  4. Near point of convergence and fusional amplitudes Correct answer.

Explanation

Fusional convergence exercises target convergence ability, so the near point of convergence and fusional amplitudes are the relevant outcome measures. Visual acuity, pupil diameter, and corneal thickness do not reflect convergence function.

Question 26Orthoptic education and clinical/education competencies (standards set by the AOC)

Which visual acuity notation expresses the size of the smallest optotype a patient can resolve as a decimal fraction?

  1. Cycles per degree
  2. LogMAR score
  3. Snellen fraction
  4. Decimal acuity Correct answer.

Explanation

Decimal acuity converts the Snellen fraction into a single number (6/12 becomes 0.5) and is widely used in European orthoptic practice. LogMAR and cycles per degree are alternative scales, and the Snellen fraction itself is written as a ratio rather than a decimal value.

Question 27Orthoptic education and clinical/education competencies (standards set by the AOC)

When recording a manifest deviation with the prism cover test, the prism is placed in front of which eye and in which orientation?

  1. The deviating eye, apex towards the deviation Correct answer.
  2. The fixating eye, base towards the deviation
  3. The deviating eye, base towards the deviation
  4. The fixating eye, apex towards the deviation

Explanation

The prism is held before the deviating eye with its apex pointing in the direction of the deviation so that the image is displaced onto the fovea and the movement is neutralised. Placing the prism over the fixating eye measures the deviation differently and is not the standard technique.

Question 28Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient reads 6/60 on the Snellen chart but identifies the individual letters of the 6/24 line when shown one at a time. Which term describes this discrepancy?

  1. Binocular summation
  2. Cortical magnification
  3. Crowding phenomenon Correct answer.
  4. Optokinetic response

Explanation

Crowding is the reduced ability to resolve letters presented in a line compared with the same letters shown singly, and it is exaggerated in amblyopia. The single-letter acuity is therefore recorded separately because it overestimates functional vision.

Question 29Orthoptic education and clinical/education competencies (standards set by the AOC)

Which colour filter is used in the Worth 4-dot test to dissociate the two eyes while allowing a red-sensitive eye to see the red dot?

  1. Red filter over the right eye and green over the left Correct answer.
  2. Neutral density filters of unequal density
  3. Polarising filters in crossed orientation
  4. Green filter over the right eye and red over the left

Explanation

The standard arrangement places a red filter before the right eye and a green before the left, so the red dot is visible only to the right eye and the green dots only to the left. The dissociation produced reveals suppression, diplopia or fusion.

Question 30Orthoptic education and clinical/education competencies (standards set by the AOC)

Which muscle is the primary depressor of the eye in adduction?

  1. Inferior rectus
  2. Superior oblique Correct answer.
  3. Inferior oblique
  4. Medial rectus

Explanation

The superior oblique has its main depressor action when the eye is adducted, because its tendon passes through the trochlea and pulls the posterior globe upward and inward. The inferior rectus depresses mainly in abduction.

Question 31Orthoptic education and clinical/education competencies (standards set by the AOC)

In a patient with a left homonymous hemianopia, which visual field defect is present?

  1. Loss of the right half of each monocular field Correct answer.
  2. Loss of the left half of each monocular field
  3. Loss of the nasal field of the right eye only
  4. Loss of the temporal field of the left eye only

Explanation

A left homonymous hemianopia denotes loss of the left visual field in both eyes, which corresponds to the right half of each monocular field because the nasal field of one eye and temporal field of the other are affected together. The defect lies posterior to the chiasm.

Question 32Orthoptic education and clinical/education competencies (standards set by the AOC)

Which instrument is used to measure the deviation objectively while the patient fixates a distant target with accommodation controlled?

  1. Perimeter
  2. Synoptophore
  3. Hess chart
  4. Prism bar with cover test Correct answer.

Explanation

A prism bar combined with the cover test neutralises the deviation while the patient fixates a distant target, giving an objective measurement of the angle. The synoptophore and Hess chart assess sensory status or incomitance rather than a simple distance angle.

Question 33Orthoptic education and clinical/education competencies (standards set by the AOC)

Which condition is characterised by a constant, large-angle esotropia present from birth or early infancy with cross-fixation?

  1. Infantile esotropia Correct answer.
  2. Accommodative esotropia
  3. Intermittent exotropia
  4. Duane retraction syndrome

Explanation

Infantile esotropia presents before about six months with a large, constant angle and cross-fixation, often with latent nystagmus and inferior oblique overaction. Accommodative esotropia appears later with hypermetropia and is intermittent at onset.

Question 34Orthoptic education and clinical/education competencies (standards set by the AOC)

A 4-year-old with a moderate hypermetropic astigmatism is found to have reduced acuity in one eye with no strabismus. Which term describes this form of amblyopia?

  1. Strabismic amblyopia
  2. Deprivation amblyopia
  3. Amblyopia of unknown cause
  4. Anisometropic amblyopia Correct answer.

Explanation

Anisometropic amblyopia arises when unequal refractive error produces a chronically defocused retinal image in one eye without a manifest deviation. Deprivation amblyopia requires an obstruction such as cataract or ptosis.

Question 35Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient with anisometropic amblyopia wears the full spectacle correction. Which additional step is most appropriate before considering occlusion?

  1. A period of spectacle wear alone to assess improvement Correct answer.
  2. Prescribing a prism to the amblyopic eye
  3. Immediate part-time patching of the better eye
  4. Commencing atropine penalisation at once

Explanation

Refractive correction alone can improve acuity substantially in anisometropic amblyopia, so a period of spectacle wear is the accepted first step before adding occlusion or penalisation. Patching or atropine before this assessment may be premature.

Question 36Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient reports diplopia that is worse on right gaze and improves on left gaze. Which deviation pattern is most consistent with this report?

  1. Alternating esotropia equal in all positions
  2. Right esotropia greater on right gaze Correct answer.
  3. Right hypertropia greater on left gaze
  4. Left exotropia greater on left gaze

Explanation

Diplopia worsens when the affected muscle is required to act, so a right esotropia that increases on right gaze suggests a right medial rectus or left lateral rectus weakness. Equal deviations in all positions are comitant and do not vary with gaze.

Question 37Orthoptic education and clinical/education competencies (standards set by the AOC)

A child has an esotropia that is present at near but absent at distance, with a high hypermetropic correction. Which mechanism explains the near deviation?

  1. Weakness of the lateral rectus muscles
  2. Excess accommodative convergence for the near demand Correct answer.
  3. Undercorrection of the hypermetropia at distance
  4. Age-related reduction in fusional reserves

Explanation

In convergence excess esotropia, the near demand evokes more accommodative convergence than the fusional divergence can offset, producing a near deviation while distance alignment is maintained. It is managed by reducing the accommodative drive or by bifocal addition.

Question 38Orthoptic education and clinical/education competencies (standards set by the AOC)

Which measurement is used to quantify the amplitude of accommodation in a cooperative child?

  1. Push-up or minus lens technique Correct answer.
  2. Stereopsis test with graded circles
  3. Prism bar cover test
  4. Bagolini striated glasses

Explanation

Amplitude of accommodation is measured by bringing a target closer until it blurs (push-up) or by adding minus lenses until blur (minus lens method). The other techniques assess alignment or binocular sensory status.

Question 39Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient with convergence insufficiency reports asthenopia after reading. Which finding on examination would support the diagnosis?

  1. Remote near point of convergence with reduced positive fusional vergence at near Correct answer.
  2. Increased amplitude of accommodation for age
  3. Exodeviation greater at distance than at near
  4. Reduced distance visual acuity with a normal near point of convergence

Explanation

Convergence insufficiency is characterised by a receded near point of convergence and reduced positive fusional vergence at near, with the exodeviation typically greater at near than at distance. Symptoms are provoked by sustained near work.

Question 40Orthoptic education and clinical/education competencies (standards set by the AOC)

Which sensory test assesses the presence of a suppression scotoma by presenting dissimilar targets to each eye?

  1. Prism reflex test
  2. Bagolini striated glasses
  3. Titmus stereo test
  4. Worth 4-dot test Correct answer.

Explanation

The Worth 4-dot test presents dissimilar coloured targets to each eye, so suppression is revealed when a patient reports fewer than four lights. Bagolini glasses use similar targets and assess the quality of binocular single vision.

Question 41Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient with a long-standing left sixth nerve palsy is examined. Which finding is expected on attempted left gaze?

  1. The left eye remains short of the midline with the right eye abducting fully Correct answer.
  2. The left eye adducts excessively with retraction
  3. Both eyes show equal limitation of abduction
  4. The left eye elevates on adduction

Explanation

A left sixth nerve palsy limits abduction of the left eye, so on left gaze the right eye abducts fully while the left eye lags, producing an incomitant esotropia. Retraction or elevation on adduction suggests a different motility disorder.

Question 42Orthoptic education and clinical/education competencies (standards set by the AOC)

Which outcome best reflects the sensory goal of treatment in a child with a small-angle esotropia and anomalous retinal correspondence?

  1. Reducing the angle to less than 5 prism dioptres
  2. Eliminating all stereopsis to avoid confusion
  3. Achieving a cosmetically straight eye in primary position
  4. Restoring normal retinal correspondence with peripheral fusion Correct answer.

Explanation

The sensory aim is to restore normal retinal correspondence and useful peripheral fusion, which supports stable binocular single vision. A purely cosmetic result does not address the underlying sensory adaptation.

Question 43Orthoptic education and clinical/education competencies (standards set by the AOC)

A child with intermittent exotropia shows a well-controlled deviation at distance and orthophoria at near. Which management is most appropriate initially?

  1. Observation with regular review and advice on control Correct answer.
  2. Full-time occlusion of the deviating eye
  3. Long-term miotic therapy
  4. Immediate bilateral lateral rectus recession

Explanation

Well-controlled intermittent exotropia with orthophoria at near often requires only observation and monitoring of control, since many children remain stable. Surgery is reserved for deteriorating control, increasing angle or functional symptoms.

Question 44Orthoptic education and clinical/education competencies (standards set by the AOC)

Which principle explains why a prism can relieve diplopia in a small comitant esotropia?

  1. The prism permanently weakens the overacting muscle
  2. The prism shifts the retinal image onto the fovea of the deviating eye Correct answer.
  3. The prism reduces the amplitude of accommodation
  4. The prism eliminates the need for fusion

Explanation

A prism displaces the image so that it falls on the fovea of the deviating eye, allowing the patient to fuse without adopting an abnormal head posture. It does not alter muscle strength or accommodation.

Question 45Orthoptic education and clinical/education competencies (standards set by the AOC)

Which factor most strongly predicts a good response to amblyopia treatment in a school-aged child?

  1. A history of previous patching failure
  2. Younger age at the start of treatment Correct answer.
  3. A large angle of strabismus
  4. Poor compliance with spectacle wear

Explanation

Younger age at treatment onset is consistently associated with better outcomes because the visual system retains greater plasticity. Compliance and adherence also matter, but age is the strongest single predictor.

Question 46Orthoptic education and clinical/education competencies (standards set by the AOC)

A researcher randomises children to two occlusion regimens and conceals allocation. Which design element most protects against selection bias?

  1. Intention-to-treat analysis
  2. Allocation concealment at randomisation Correct answer.
  3. Use of a per-protocol analysis
  4. Blinding of the outcome assessor

Explanation

Allocation concealment prevents investigators from anticipating the next assignment, which is the specific defence against selection bias at the point of randomisation. Assessor blinding and intention-to-treat analysis address different biases.

Question 47Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient has a left superior oblique palsy. Which compensatory head posture is most likely to be adopted?

  1. Head tilt to the left with chin depression
  2. Head turn to the right with chin elevation
  3. Head turn to the left with chin depression
  4. Head tilt to the right with chin elevation Correct answer.

Explanation

A left superior oblique palsy produces a left hypertropia that worsens on right gaze and right head tilt, so patients typically tilt the head to the right and may elevate the chin to minimise the deviation. The posture keeps the eyes in the field where the deviation is least.

Question 48Orthoptic education and clinical/education competencies (standards set by the AOC)

A patient with a long-standing constant esotropia develops suppression of the deviating eye. Which mechanism best explains the suppression?

  1. Reduced corneal sensitivity in the deviating eye
  2. Cortical inhibition of the conflicting image from the deviating eye Correct answer.
  3. Mechanical restriction of the medial rectus
  4. Loss of accommodation in the deviating eye

Explanation

Suppression is a cortical adaptation that inhibits the image from the deviating eye to prevent diplopia and confusion. It is not caused by refractive, mechanical or corneal factors.

Question 49Orthoptic education and clinical/education competencies (standards set by the AOC)

Which statement best describes the orthoptist's role in a multidisciplinary ophthalmology team?

  1. Performing sensory and motor orthoptic assessment and directing non-surgical treatment Correct answer.
  2. Prescribing systemic medication for motility disorders
  3. Performing intraocular surgery for strabismus
  4. Interpreting histopathology of extraocular muscle biopsy

Explanation

The orthoptist provides sensory and motor assessment, diagnostic testing and non-surgical management such as occlusion, prisms and exercises, working alongside ophthalmologists. Prescribing systemic drugs, surgery and histopathology lie outside the orthoptic scope.

Question 50Orthoptic education and clinical/education competencies (standards set by the AOC)

Which outcome measure is most appropriate for evaluating a fusional convergence exercise programme?

  1. Change in pupil diameter
  2. Change in refractive error
  3. Change in distance visual acuity
  4. Change in positive fusional vergence at near Correct answer.

Explanation

Fusional convergence exercises aim to improve the ability to converge against base-out prism, so positive fusional vergence at near is the direct outcome measure. Visual acuity, refraction and pupil size are not the targets of the programme.