Principles of BSV

• What is Binocular Single Vision (BSV)?

  BSV is the ability to use both eyes simultaneously for a common single perception.
• What characterizes normal binocular single vision?

  Normal BSV is bifoveal with no manifest deviation.
• What indicates abnormal binocular single vision?

  Abnormal BSV occurs when there is a manifest deviation and BSV is achieved in free space.
• What are the advantages of normal BSV?

  Normal BSV allows depth perception, a large field of vision, and enhanced visual-motor skills.
• What is Binocular Single Vision (BSV)?

  BSV is the ability to use both eyes simultaneously for a common single perception.
• What characterizes normal binocular single vision?

  Normal BSV is bifoveal with no manifest deviation.
• When is abnormal binocular single vision present?

  Abnormal BSV occurs when there is a manifest deviation and BSV is achieved in free space.
• What does normal BSV allow us to see?

  Normal BSV allows us to see one image despite having two eyes.
• What advantage does normal BSV provide in terms of depth perception?

  Normal BSV allows for depth perception or stereopsis.
• What are some advantages of normal BSV?

  Advantages include fine judgments of object positions, a large field of vision, and enhanced visual-motor skills.
• What are the factors affecting the development of normal BSV?

  • Normal anatomical development of the eyes
  • Associated connections in the brain and skull
  • Normal development of the fovea
  • Overlap of visual fields
  • Crossing of nasal retinal fibers at the chiasm
  • Normal retinal correspondence
• What is the role of the right visual field in BSV?

  Fibres from the right nasal and left temporal retina relay information to the left visual cortex.
• What is the role of the left visual field in BSV?

  Fibres from the left nasal and right temporal retina relay information to the right visual cortex.
• What is the significance of the optic chiasm in visual processing?

  Nasal retinal fibres cross at the optic chiasm, allowing for proper visual field processing.
• How does projection relate to BSV?

  Projection is the subjective interpretation of the direction of an object as seen by the eyes.
• What is normal retinal correspondence (NRC)?

  NRC is a binocular condition where corresponding retinal areas in both eyes have a common visual direction.
• What happens when corresponding points in each eye are stimulated?

  Stimulation results in a single mental image being formed.
• What is the horopter?

  The horopter is the locus of all object points that are imaged upon corresponding retinal elements at a given fixation distance.
• What is the significance of the Vieth-Müller circle?

  The Vieth-Müller circle is a theoretical circle that contains points falling on corresponding retinal locations in the two eyes.
• What is Panum's fusional space?

  • Area where objects are seen singly
  • Corresponding points must be stimulated
  • Space is narrower centrally than peripherally
  • Corresponding area on the retina is Panum’s fusional area
• What is physiological diplopia?

  Physiological diplopia occurs when objects are not lying on the horopter or in Panum’s fusional space, resulting in double vision.
• What are the two types of physiological diplopia?

  Homonymous (uncrossed) and heteronymous (crossed) diplopia.
• What are the characteristics of BSV?

  • Simultaneous perception
  • Sensory fusion
  • Motor fusion
  • Stereopsis
• What is simultaneous perception in BSV?

  Simultaneous perception is the ability to appreciate two images at the same time, one from each retina.
• What is sensory fusion?

  Sensory fusion is the ability to see two similar images as one single image.
• What is motor fusion?

  Motor fusion is the ability to maintain sensory fusion through a range of vergence movements.
• What is retinal rivalry?

  Retinal rivalry occurs when dissimilar images are presented to corresponding retinal areas, making fusion impossible.
• What is stereopsis?

  Stereopsis is the ability to perceive depth through the horizontal separation of the two eyes.
• How does stereopsis develop in humans?

  Stereopsis develops between 3-4 months of age, starting with gross stereopsis and gradually building to adult levels.
• What is stereoacuity?

  Stereoacuity is the measurement of the minimum disparity giving rise to stereopsis.
• How is stereoacuity measured?

  Stereoacuity is generally measured in seconds of arc.
• What are monocular cues to depth perception?

  • Texture Gradient
  • Linear Perspective
  • Occlusion
  • Relative Size
  • Highlights & Shadows
  • Aerial Perspective
• What is motion parallax?

  Motion parallax is the apparent motion of objects relative to us based on their distance from the fixation point.
• What is the cover test used for?

  • Qualitative test for BSV
  • Indicates presence and level of BSV
  • Detailed coverage in future sessions
• What are the methods for testing simultaneous perception and sensory fusion?

  • Worth lights
  • Bagolini glasses
  • Polarised four-dot
• How are Bagolini glasses tested?

  Bagolini glasses can be tested at 1/3m and 6m with refractive correction.
• What should always be worn when testing with Bagolini glasses?

  Refractive correction for that distance
• What are the possible responses when using Worth Lights?

  Pt Left, Pt Right, BSV, Heteronymous Diplopia, Homonymous Diplopia, Left Suppression, Right Suppression
• What type of glasses are worn during the Polarised Four-Dot Test?

  Polarising glasses
• What is the significance of motor fusion in the management of squint?

  It plays a major role in the management of squint