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
- Sensory and Motor tests
- Stereopsis tests
- Measurements of ocular misalignment
- 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
- Contrast of gratings are equal to the contrast of the background
- Observe patient eyes - theory that gratings (stripes) will attract
- Difficult interpretation patients with nystagmus
- Limited interest
- ?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
- 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
- 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
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
- Use to identify misalignments
- Differentiate between phoria(imbalance) and tropia (squint)
- If phoria - determine how well controlled by assessing recovery movement
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?)
45deg / exo
Corneal reflections displaced temporally = esodeviation
Corneal reflections displaced nasally = exodeviation
? Left eye deviated outwards (exotropia/ (squint)
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.
- 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.
- 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
- 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
Measurements of ocular misalignment Stereopsis (3-D Vision)
- Strong ability to co-ordinate the eyes and process information from
- Measure grades of stereopsis
- Variety of tests - suited to age and abilities.
- Lang Stereotest/Wirt
- Quick and easy to use
- Good for younger children - (I personally use only if other methods have failed)
- Some limitations
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
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.
- Emmetropia / no refractive error
- Myopia - shortsightedness
- Hyperopia -(hypermetropia) longsightedness
Taken from www.merck.com
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
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