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An Overview of the Orthoptist Practical Demonstration The Cover Test

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

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  1. An Overview of the OrthoptistPractical DemonstrationThe Cover Test Louise.C.Corp Senior Orthoptist

  2. 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

  3. Vision Assessment ‘Hundreds and thousands’ sweet test Preferential looking with Cardiff cards

  4. At age 2 years (naming pictures) Kay single picture Multiple pictures At age 3 years (matching tests) Sheridan-Gardiner Sonksen-Silver

  5. 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

  6. Managing Vision Defects • AMBLYOPIA – “Lazy Eye” – Reduced vision in one or both eyes • Causes – refractive error, squint, stimulus deprivation (ptosis or cataract) Patches Atropine Penalisation Glasses Blenderm Optical Penalisation

  7. 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

  8. Defects of Binocular Single VisionSquints

  9. There are two types of Strabismus

  10. 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. • HORIZONTAL • VERTICAL • TORSIONAL

  11. Horizontal • Convergent - one eye deviates nasally (turns inwards) ESOTROPIA • Divergent - one eye deviates temporally (turns outwards) EXOTROPIA

  12. What type of squint do these patients have? RIGHT CONVERGENT SQUINT LEFT DIVERGENT SQUINT Reflex at limbus = 45 Reflex at border of pupil = 15

  13. Pseudo-Strabismus Pseudo-Esotropia Pseudo-Exotropia • Epicanthic folds • Wide interpupillary distance • Short interpupillary distance

  14. Essential Infantile Esotropia Presents within first 6 months Signs • Angle large and stable • Nystagmus in some cases • Normal refraction for age • Poor potential for BSV • Amblyopia in about 30% • Cross fixation

  15. Constant Exotropia Congenital Sensory • 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

  16. The effect of glasses The effect of accommodation

  17. Ocular Motility Defects Abnormal Eye Movements

  18. Third Nerve Palsy • Ptosis, mydriasis and cycloplegia • Abduction in primary position • Normal abduction • Intorsion on attempted • downgaze • Limited adduction • Limited elevation • Limited depression THE PATIENT WILL SUFFER DIPLOPIA

  19. Sixth Nerve Palsy Straight in primary position due to partial recovery Limitation of right abduction and horizontal diplopia Normal right adduction

  20. 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

  21. Thyroid Eye Disease Elevation defect - most common Abduction defect - less common Depression defect - uncommon Adduction defect - rare

  22. Right Brown`s Syndrome Normal elevation in abduction Straight in primary position Limited elevation in adduction Defect to the Superior Oblique Muscle / Tendon

  23. EYE MOVEMENTS PLOTTED USING THE LEES SCREEN HESS CHART

  24. DIPLOPIA HORIZONTALVERTICAL MAY REQUIRE THE USE OF FRESNEL PRISMS

  25. 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 BE CAREFUL!! • 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

  26. Does anyone in the group have a squint? Let`s find out ???

  27. 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.

  28. 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

  29. Continued…………….. • 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

  30. Possible findings for Manifest Squint

  31. Continued………… • 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

  32. 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)

  33. Continued………... • 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

  34. Remember……………. • 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

  35. Thank you Louise.C.Corp Orthoptic Dept Calderdale Royal Hospital 01422 222218

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