University of Edinburgh

Course: Visual Assessment of Children: The Orthoptist Role

Presented on Wednesday 9 February 2005

Orthoptic Tests and Refraction
Making knowledge work

Jennifer Skillen Orthoptist/Researcher
Royal Alexandra Eye Pavilion/University of Bradford

presented in February 2005

Role of Orthoptist

  • Screening of pre-school/school age children
  • Monitoring vision/binocular status/motility ? repeat assessments/measurements
  • Treatment of amblyopia - occlusion/penalisation
  • Treatment of binocular vision weaknesses ? manipulation of glasses prescription/exercises/prisms
  • Extended role also includes - low vision/ visual stress/ stroke rehab/glaucoma monitoring to name but a few.

How do we achieve these aims?

Battery of tests

Vision Test

  • Selection of tests appropriate age and abilities of patient
  • Measurement of uni-ocular vision - use patch
  • Comparison of visual responses R and L eyes
  • Measurement of binocular acuity - esp. patients with nystagmus

Preferential Looking

  • Contrast of gratings are equal to the contrast of the background
    contrast gratings
  • Observe patient eyes - theory that gratings (stripes) will attract attention
  • Difficult interpretation patients with nystagmus
    gratings tests
  • Limited interest

Cardiff Cards

  • ?Vanishing optotype? - pre-verbal (1 year+)
  • Maintain interest
  • Vertical separation
    using cardiff cards
  • Short distance (50cm/100cm)
  • good interaction for babies/toddlers
  • 11 acuity levels
  • Overestimation of acuity
    cardiff cards

Kay Pictures

  • Verbal/matching abilities (2 years +)
  • Single and Crowded format
  • 12 equal step sizes
  • Logmar test can be done at any distance
    kay picture tests

Logmar Crowded Test

  • Glasgow Acuity Cards/Keeler logmar test (1993)
  • Excellent design - Logmar acuity preferable to Snellen acuity
  • Single and Crowded acuity
  • Test distance 3m standard but any distance possible
    logmar crowded test


  • Adult VA test
  • Replaced by Logmar (children acuity measurements)
  • Unequal number of letters - crowding effect not equal/controlled.
    snellen test

Near Visual Acuity

  • Single/crowded versions
  • Older children sample texts of different sizes - age specific
  • Nystagmus/Low Vision (nVA often better than dVA
    visual acuity test


Cover Test

Detection of squints/misalignments of the eyes

  • Quick and easy test
  • Any age of patient
  • Selection of target - dependent on visual abilities - light/toy/fixation stick - pictures/letters


  • Observe corneal reflections
  • Do cover/uncover test then alternating cover test
  • Many classification of squints/misalignments but basic form
    • ? in(eso) out(exo)up(hyper) down(hypo) or a combination.
    • ? Constant - Tropia
    • ? Intermittent -Phoria->Tropia
    • ? Variation -near/distance

Cover Test

  • Use to identify misalignments
  • Differentiate between phoria(imbalance) and tropia (squint)
  • If phoria - determine how well controlled by assessing recovery movement

    cover test

Phorias, ie; esophoria/exophoria

  • Phoria - misalignment of the visual axis revealed by dissociation of the eyes.
  • Common small amount of phoria - but can results in disruption to BSV (Binocular Single vision)
    • ? problematic - small phoria but inadequate fusional abilities or phoria too large in size to be controlled by normal fusional amplitudes.
    • ? results in blurred/double vision in adults and older children.
    • ? Younger children - may not be aware of symptoms

Decompensated Phoria = Intermittent Tropia

Tropias - Hirschberg technique


Corneal reflections central and symmetrical. Rule: 1mm = 20? (approx. 11?)


15 deg eso

15deg/ eso


20/25 deg eso

20/25deg/ eso


45 deg exo

45deg / exo

Corneal reflections displaced temporally = esodeviation

Corneal reflections displaced nasally = exodeviation

Cover/Uncover Test

Alternating SOT

alternating SOT

Cover Test

? Left eye deviated outwards (exotropia/ (squint)

cover test

Covering the fixing eye(R eye) - L eye moves inwards



  • Assessment of muscle function in 9 different gaze positions.
  • Any age - quick and easy test.
  • Can be used in conjunction with the cover test - no squint/misalignment straight ahead but present when looking in one particular gaze.
  • Present light - observe corneal reflections and patient instructed to follow target.

Motility test

motility test

motility test


Sensory and Motor Status

  • The ability of the two eyes to integrate visual information (sensory) over a range of obstacles (motor).
  • Can information from both eyes be combined? If so how well is that information combined if the person has phoria/is tired/poor general health?
  • Normal state -6 muscles around each eye are all functioning and the motor system continuously makes small corrective eye movements - maintains the integrity of the info from both eyes.

Sensory Fusion

  • Present each eye with different stimulus
  • If sensory fusion intact - patient will report a combined percept.
  • Variety of different test - Bagolini glasses
  • Constant squint - supn/diplopia(double vision)
    sensory fusion
  • Worth?s Lights
  • Near and Distance Test
  • More dissociative than previous test
    worth's lights

Motor Fusion

  • How well the combined percept holds over a range of obstacles
  • Use prisms - shift images from each eye apart
  • Observe whether the motor system can react and combine the percept
  • 20^ Test in children
  • Full fusion range in older children using prism bar
    motor fusion


Stereopsis tests

Measurements of ocular misalignment Stereopsis (3-D Vision)

  • Strong ability to co-ordinate the eyes and process information from each eye.
    using stereopsis test
  • Measure grades of stereopsis
  • Variety of tests - suited to age and abilities.
    stereopsis tests

Other Stereotests

  • Lang Stereotest/Wirt
  • Quick and easy to use
  • Good for younger children - (I personally use only if other methods have failed)
  • Some limitations
    other stereotests


Measurements of ocular misalignment

Measurement of squints/misalignments

  • Synoptophore - picture test
  • Measure - misalignments,sensory and motor fusion and stereopsis
  • Predict BV post-surgery
  • Measure misalignments 9 positions of gaze
    synoptophore - measurement of misalignment

Prism Cover Test

  • Measure squint/misalignment
  • Single prism/prism bar
  • Primary position or in all positions of gaze

prism cover test

prism cover test

Reaching a diagnosis

  • Tests will be used in many different ways for different patients
  • Requires a Refraction(glasses test) and Fundus/Media review (health of the eyes)
  • It may take a few visits to reach a full diagnosis
  • Once a diagnosis has been reached then formulate a treatment plan


  • Test used to identify refractive error ? Long-sightedness (hyperopia) ? Short-sightedness(myopia) ? astigmatism.
  • Normally carried out by Optometrist (Optician) or by Ophthalmologist (medical eye doctor) - or in some clinics by an orthoptist (rare).
  • Can be carried out at any age.
  • Normally use eye drops in children.
  • High prevalence of refractive errors in patients with squints/reduced acuity.

Refractive Errors

  • Emmetropia / no refractive error
  • Myopia - shortsightedness
  • Hyperopia -(hypermetropia) longsightedness

refractive errors

Taken from


Use Retinoscope - streak retinoscopy common






If astigmatism present - reflex will be off-axis - neutralise in one plane and then the other

Relevance of Refractive error on Misalignments

  • Manipulation of refractive error common
    • - try and increase + to aid control of eso try and increase
    • - to aid control of exo
  • High powers -
    • ? need midway/partial Rx - build up tolerance
    • ? Use drops to encourage tolerance Next Step?
  • Reach optimum acuity levels - glasses, patching, penalisation
  • Strengthen Binocular functions - glasses, exercises, prisms and/or surgery
  • Improve cosmetic appearance of squints - surgery
  • Improve motility - surgery

Eye Exercises/Free Space Techniques

eye exercises

How is this achieved?

  • By teamwork
    • - linking professions within the eye clinic
    • - orthoptist
    • - optometrist and Ophthalmologist
    • - with good communication with parents and patients.
  • Multi-disciplinary approach