Scottish Sensory Centre

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 Tests
• Cover Test
• Motility
• Sensory and Motor tests
• Stereopsis tests
• Measurements of ocular misalignment

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
  
  
• Observe patient eyes - theory that gratings (stripes) will attract attention
  
• Difficult interpretation patients with nystagmus
  
  
• Limited interest

www.science.ulst.ac.uk

Cardiff Cards

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

www.science.ulst.ac.uk

Kay Pictures

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

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
  

Snellen

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

Near Visual Acuity

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

 

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

TROPIA/PHORIAS

• 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
  

  Esophoria
  

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?)

 

15deg/ eso

 

20/25deg/ eso

 

45deg / exo

Corneal reflections displaced temporally = esodeviation

Corneal reflections displaced nasally = exodeviation

Cover/Uncover Test

Alternating SOT

Cover Test

? Left eye deviated outwards (exotropia/ (squint)

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

 

Motility

• 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

 

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)
  
  
• Worth?s Lights
• Near and Distance Test
• More dissociative than previous test
  

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
  

 

Stereopsis tests

Measurements of ocular misalignment Stereopsis (3-D Vision)

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

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
  

 

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
  

Prism Cover Test

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

www.ophthalmic.hyperguides.com

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

Refraction

• 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

Taken from www.merck.com

Refraction

Use Retinoscope - streak retinoscopy common

Myopia

Hyperopia

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

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

Where next

• Visual Assessment of Children: The Orthoptist Role