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An Overview of the Orthoptist Practical Demonstration The Cover Test. Louise.C.Corp Senior Orthoptist. The Role of the Orthoptist. Assess and Manage: Vision Defects (Amblyopia) Vision Screening Defects of Binocular Single Vision (Squint) Ocular Motility Defects Low Vision Assessment

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An overview of the orthoptist practical demonstration the cover test l.jpg

An Overview of the OrthoptistPractical DemonstrationThe Cover Test


Senior Orthoptist

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The Role of the Orthoptist

Assess and Manage:

Vision Defects (Amblyopia)

Vision Screening

Defects of Binocular Single Vision (Squint)

Ocular Motility Defects

Low Vision Assessment

Glaucoma Clinics

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Vision Assessment

‘Hundreds and thousands’ sweet test

Preferential looking with

Cardiff cards

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At age 2 years (naming pictures)

Kay single picture

Multiple pictures

At age 3 years (matching tests)



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Expectations of a baby

  • To be able to fix and follow small toys ( e.g. mobile whilst in their cot), lights.

  • Respond to facial expression ( e.g. confirmed by baby smiling, laughing, following parents face on movement ).

  • Baby will attempt to grasp for small toys whilst fixating on them (e.g play frame over the child whilst laying on their back on the floor)

  • At birth - VA approx 6/240 - Improvement rapid in first 6mths with a slower rate up until 12mths

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Managing Vision Defects

  • AMBLYOPIA – “Lazy Eye” – Reduced vision in one or both eyes

  • Causes – refractive error, squint, stimulus deprivation (ptosis or cataract)


Atropine Penalisation



Optical Penalisation

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Vision Screening

  • Reception Class (4 - 5yrs)

  • Vision, Check for Squint, Assess BSV, Ocular Motility

  • Pass / Fail Criteria

  • Absentees offered appointment at Community Clinic or re-visit school

  • Referred to: Orthoptic Clinic, Hospital Optician, Consultant, High street Optician

  • 96% coverage 83% passed 5.4% referred to optician 4.8% referred to CRH 1% referred to community clinic as borderline results 4% absent but offered test at community clinic close to home

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Manifest Strabismus

  • Also known as HETEROTROPIA

  • When one eye focuses on an object, one eye deviates away from the object

  • Squint is caused by failure of two eyes to look at objects in a coordinated manner. Depends on the normal functioning of brain, optic nerve and twelve muscles around our eyes enabling the two images to superimpose on each other and to form a three dimensional image.




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  • Convergent - one eye deviates nasally (turns inwards) ESOTROPIA

  • Divergent - one eye deviates temporally (turns outwards) EXOTROPIA

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What type of squint do these patients have?



Reflex at limbus = 45

Reflex at border of pupil = 15

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  • Epicanthic folds

  • Wide interpupillary distance

  • Short interpupillary distance

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Essential Infantile Esotropia

Presents within first 6 months


  • Angle large and stable

  • Nystagmus in some cases

  • Normal refraction for age

  • Poor potential for BSV

  • Amblyopia in about 30%

  • Cross fixation

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Constant Exotropia



  • Presents at birth

  • Disruption of binocular reflexes by

  • acquired lesions, such as cataract

  • Large angle

  • Alternating fixation

  • Normal refraction for age

Consecutive - follows previous surgery for esotropia

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The effect of glasses

The effect of accommodation

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Ocular Motility Defects

Abnormal Eye Movements

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Third Nerve Palsy

  • Ptosis, mydriasis and cycloplegia

  • Abduction in primary position

  • Normal abduction

  • Intorsion on attempted

  • downgaze

  • Limited adduction

  • Limited elevation

  • Limited depression


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Sixth Nerve Palsy

Straight in primary position due to partial


Limitation of right abduction and

horizontal diplopia

Normal right adduction

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NERVE PALSIES (III,IV,VI) Be aware in Children

Present with acute onset Squint

Complaining of Diplopia

Parents notice closing of one eye

Urgent referral

Serious Pathology

More common 6th Nerve Palsy

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Thyroid Eye Disease

Elevation defect - most common

Abduction defect - less common

Depression defect - uncommon

Adduction defect - rare

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Right Brown`s Syndrome

Normal elevation in


Straight in primary position

Limited elevation in


Defect to the Superior Oblique Muscle / Tendon

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What to refer to an Orthoptist ??

  • Yes

  • Vision concerns – baby not fixing/following small toy / lights

  • Squint

  • Ocular Movement concerns

  • Poor cooperation of patient to ensure no defects

  • Parental Concern


  • No

  • Family History alone – distant relatives

  • If ? A squint in a child < 4 months old if obvious squint seen then refer if not ask HV to check at 6mths, if still doubtful then refer

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The Cover Test

  • “An objective dissociation test to elicit the presence of a manifest or latent deviation. It relies upon the observation of the eyes whilst fixation is maintained and each eye is covered and uncovered in turn”.

  • Firstly, check for a manifest squint before progressing to find a latent squint.

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Detection of a manifest squint

  • Ensure patient is looking straight ahead

  • A light is used initially as the position of corneal reflections may indicate a manifest squint  should be central / symmetrical or both displaced slightly nasal

  • Hold fixation target on a level with patients eyes at a 1/3m and ask them to look at it

  • Introduce occluder in front of one eye and watch for any movement of the other eye

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  • If there is no movement, repeat with the occluder in front of the other eye

  • If no movement visible then the patient DOES NOT have a manifest squint at that fixation distance

  • Repeat CT at 6m and far distance if necessary

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Possible findings for Manifest Squint

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  • Performed at 1/3m, 6m and far distance

  • Using accommodative/non-accommodative fixation targets

  • With and without glasses

  • With or without any Abnormal Head Posture

  • In 9 positions of gaze if required

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Detection of a latent squint

  • Use appropriate accommodative/non-accommodative targets on a level with the patients eyes at 1/3m

  • Introduce occluder in front of one eye

  • Observe for any movement of the eye behind the occluder once it is removed

  • Repeat with other eye

  • If no movement seen, alternate the occluder from eye to eye (make sure binocularity is avoided)

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  • A movement maybe more obvious as alternate eyes are occluded

  • Size and direction of movement of the occluded eye as it is moved over to the other eye should be noted

  • Speed at which the eye moves back to the normal position as the occluder is completely removed should be noted (rate of recovery) – indicates strength of BSV or vision level

  • Repeat at 6m

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  • Position of eyes on appearance

  • Check corneal reflections first

  • Ensure no manifest deviation present first

  • Estimate size of deviation (minimal,slight,mod,mkd) and direction of deviation

  • Fixation targets-light,small picture or toy, 6m picture/object

  • Can the manifest deviation alternate or hold fixation

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Thank you


Orthoptic Dept

Calderdale Royal Hospital

01422 222218