binocular vision

• Binocular vision

  Coordinate use of "BOTH EYES" – produce single mental image
• Fusion

  Blending of sight to form a single percept
• Combination of left to right retinal image forms fusion which makes the vision single
• Binocular vision

  • Taken into consideration to check the integrity of both eyes if it can function properly
  • If both eyes cannot function simultaneously and continuously it creates binocular vision problem
  • People with 20/20 vision can still have a problem in binocular vision
• Binocular vision problems


  • Doubling of vision
  • Deviation
  • Confusion
• Healthy functioning maculas


  • Clear visual axis
  • Should not have edema (swelling)
  • No degeneration of retinal cells (rods and cones)
  • Should be working simultaneously and synchronously to maintain a clear vision axis
• Visual axis

  From the point of regard to the fovea
• Nystagmus

  Involuntary movement of both eye or one eye only resulting to loss of foveal reflex / stimulation
• Types of nystagmus

  • Horizontal nystagmus
  • Vertical nystagmus
  • Oscillating nystagmus
• Reason for nystagmus

  The eye compensates by finding the foveal stimulation to have a clear visual axis. The eye is always moving even if they are looking straight to locate the foveal stimulation.
• Efficiently working muscular mechanism

  • Extra ocular muscle – motor fusion
  • Intraocular muscles – accommodation (3 synkinetic actions) – ciliary muscle and pupillary muscle – must be coordinated
• Motor fusion

  Both eyes should converge upon looking near. There is a problem with the binocular vision if the eyes failed to converge upon looking at near, causing diplopia (doubling of vision).
• Efficiently working neural mechanism

  • Sensory fusion – brain neuroplasticity – "rewiring" of the neural connections to properly coordinate both eyes
  • Should have a good passing of stimulus to the brain to have a proper interpretation (pupillary pathway and visual pathway)
• Sight

  What you see, if you can see the target as a whole (20/20 vision)
• Vision


  Visual interpretation, you know what you see and can describe it, you know where the thing is used, capabilities, and distance from the object and the person
• Visual agnosia

  Neural defect, the area striata #17 doesn't process what they see. They cannot distinguish, describe, and know the exact distance of the object.
• Prosopagnosia

  Facial blindness, sub type of visual agnosia
• Prerequisites of binocular vision

  • Frontally placed eyes, overlapping retinal fields
  • Partially decussation of optic nerve fibers
  • Foveal region stimulated
  • Corresponding or identical retinal points
  • Size of the retinal image must be equal or nearly equal

  
• Overlapping retinal field

  When the vision in right overlaps to the vision on left eye
• Partial decussation of optic nerve fibers


  Part of the image seen by the right eyes is also seen by the left eye, and vice versa
• Corresponding or identical retinal points

  RF = LF, RN = LT, RT = LN - where all the stimulation meets (tumatama) when looking at point of regard
• Normal retinal correspondence

  All angles are equal, the corresponding points should follow the law to have an overlapping retinal field
• Abnormal retinal correspondence

  There is deviation or visual problems kaya nagkakaroon ng misalignment of cardinal points
• Diplopia

  Corresponding retinal correspondence are misaligned
• Strabismus

  Misalignment of the eyes
• Anomalous abnormal correspondence

  There is a misalignment of the eyes but still have a normal retinal correspondence

  
• Iseikonia

  Equal size of retinal image

  
• Aniseikonia

  Unequal size of retinal image
• Iso-oxyopsia


  Equal best corrected visual acuity

  
• Aniso-oxyopsia


  Unequal best corrected visual acuity

  
• Anisometropia


  Significant/high difference of eye refractive error

  
• Antimetropia


  Different refractive status, e.g. right eye myopic, left eye hyperopic

  
• Refractive status


  Diagnosis (myopia, hyperopia, astigmatism)
• Refractive error


  Grade of the eye (power/diopter)

  
• Efficient function of extra-ocular muscles and nerves

  • Efficiently working neural and muscular muscles
• Advantages of binocular vision

  • Single vision
  • Optical defects in one eye are made less obvious by normal image of the other eye
  • Enlarged field of vision
  • Power to discriminate details and contours of an object better with 2 eyes than with one eye alone
  • Loss of one eye will not seriously handicap the individual
  • Stereopsis and depth perception (monocular cues)
  • Compensation of blindspot and other differences

  
• Binocular visual field


  180 degrees (two eyes working, can see periphery)

  
• Common binocular field


  120 degrees (only sees the center, minus the temporal crescent)
• Monocular visual field


  150 degrees (one eye)

  
• Temporal crescent


  30 degrees (limitation of lids; restriction of)