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Assessment and Management of Strabismus. Fiona Crotty Head Orthoptist East Sussex Hospitals. Overview. Development of Visual Acuity Assessment of Vision in Infants & children What is BSV and how does it develop? Classification of squint Assessment of squint Management of squint.

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assessment and management of strabismus

Assessment and Management of Strabismus

Fiona Crotty

Head Orthoptist

East Sussex Hospitals

overview
Overview
  • Development of Visual Acuity
  • Assessment of Vision in Infants & children
  • What is BSV and how does it develop?
  • Classification of squint
  • Assessment of squint
  • Management of squint
development of visual acuity
Development of Visual Acuity
  • Dependent upon normal anatomical and physiological development
  • Eye relatively well developed in full-term infant
    • Shorter axial length (more hypermetropic)
    • Shallow anterior chamber
    • Poorly differentiated fovea (complete by 4 months age)
    • Accommodation 90% accurate by 2 – 3 months
development of visual acuity vep s
Development of Visual acuity (VEP’s)

* Tested with single optotypes

assessment of vision logmar vs snellens type
Assessment of Vision – LogMAR vs. Snellens Type
  • Snellens:
    • Traditional method
    • 6 metre test distance
    • Recorded as fraction e.g.6/60, 6/9
    • Inconsistent numbers & spacing of letters per row
  • logMAR:
    • Decimal value, 0.0 =6/6 equivalent, 0.2 = 6/9.5 etc
    • Equal number of letters per row, consistent spacing
    • Greater range of acuity values & can be used at 3m
    • Preferred method for research and amblyopia testing
assessment of vision
Assessment of Vision

Snellens Chart

logMAR Chart

what is bsv
What is BSV?
  • Definition of Binocular Single Vision (BSV)
    • The ability to use both eyes simultaneously so that each eye contributes to a common single perception
  • 3 levels
    • Simultaneous perception ( 2 images seen)
    • Fusion (Interpreting 2 images as one)
    • Stereopsis (3-D appreciation)
development of bsv
Development of BSV
  • Newborn reflexes present – essential for BSV development
  • Require continued use and normal visual experience
    • Postural reflexes: static (head position to body) and stato-kinetic (head relative to space)
    • Fixation reflexes: fixation (foveal) and re-fixation (target to target and maintained to moving object)
development of bsv1
Development of BSV

Most neonates show coarse re-fixation

  • Conjugate fixation 1st to develop (eyes follow object together)
  • Disjugate fixation (follow approaching object – convergence)
  • Fusional reflex (correct for change in image position)
  • Kinetic reflex (controlled accommodation & convergence)
development of bsv2
Development of BSV
  • From aet 4/52 Attempts at convergence seen
  • 5-6/52 conjugate fixing and brief following – neonatal misalignment common
  • 4/12 saccadic eye movements develop, neonatal misalignments reduce
  • 6/12 – 8/12 normal BSV established
risk factors for development of squint
Risk Factors for Development of Squint
  • Prematurity
  • Neuro-developmental delay
  • Motor control disorders eg cerebral palsy
  • Refractive error, failure to emmetropise
  • Family history
brief classification of squint
(Brief) Classification of Squint
  • Manifest (Heterotropia)
    • Esotropia (convergent)
    • Exotropia (divergent)
    • Vertical
    • Unilateral or alternating
    • Constant or intermittent (in Primary position, or in certain positions of gaze)
    • Accommodative
brief classification of squint1
(Brief) Classification of Squint
  • Latent (Heterophoria)
    • Esophoria
    • Exophoria
    • Vertical ‘phoria
    • Fully compensated
    • Poorly compensated
assessment of squint
Assessment of squint
  • Visual Acuity
  • Cover Test
  • Ocular Movements
  • Convergence
  • Fusion/Stereopsis?
  • Measurement of angle (prisms)
management of squint
Management of Squint
  • Orthoptic assessment
  • Cycloplegic refraction & fundoscopy
    • Correct significant refractive error
    • Allow for refractive adaptation (up to 18/52)
    • Occlusion treatment for amblyopia (patches, atropine)
    • Orthoptic exercises (intermittent deviations)
    • Surgery
summary
Summary
  • Early intermittent neonatal misalignment common between birth and 2-4 months
  • BSV well established from 6 months
  • Sensitive period for development of vision and binocular reflexes
  • Suspected squint after 4 months (corrected) age should be referred for Orthoptic assessment
acknowledgements
Acknowledgements
  • Thank you to Manuel Saldana for his kind permission to use the video clips