convergence

• Convergence


  The ability to turn the two eyes inward toward each other to look at close objects
• Physiological convergence (normal convergence)


  • Convergence only happens when looking at close objects
• Convergence

  1. Coordinated stimulation of some extraocular muscles at the same time others are relaxed

  2. Stimulation of the medial rectus muscle of both eyes while simultaneously relaxing the lateral recti muscles
• Amplitude of convergence does not deteriorate with age, unlike accommodation
• Certain convergence might be reduced under certain abnormal circumstances
• Power or reserve of convergence can be increased by orthoptic exercises
• Tropia / Strabismus

  Permanent deviation of the eye, manifested on the eye
• Esotropia


  Eyes turning inward
• Exotropia


  Eyes turning outward
• Phoria

  Not permanent deviation of the eye
• Cover and Non-Cover Test

  1. To reveal if the patient has either phoria or tropia

  2. It breaks the fusion (fusion means a combination of the image from the left and right eye, own image on diff eye), covering one eye, the uncovered eye will act alone and will not coordinate to the covered eye
• Phoria

  There is a deviation of the eye after the breaking of fusion. After removing the cover on the eye, the eyes will align again
• Tropia

  The deviation is manifested even though the fusion is not broken and both eyes are open
• Esophoria


  When the other eye is covered then the uncovered eye is turned inwards
• Exophoria


  Uncovered eye turned outwards / temporal
• Amblyopia (lazy eye / lazy brain)

  The patient doesn't achieve 20/20 standard vision even with the best correction
• Criteria to know if the patient has amblyopia 20/40 BCVA (Best Corrected Visual Acuity) or worse (20/70, 20/100) standard for checking. Even though the patient is given the best / exact eye correction they can only achieve 20/40 BCVA
• 20/30, a modern subtype of amblyopia, not categorized as amblyopia but a type
• Amblyopia

  • Can cause Tropia if the patient has ocular diseases such as cataracts and glaucoma, deprivation amblyopia
  • Can cause Tropia if the patient has uncorrected vision / refractive error especially in children
• Neuroplasticity


  Rewiring of the brain, the retina will receive stimulation and the brain will adapt to it. It will take time for the 20/20 vision to go back
• Eye dominancy

  The brain favors a certain eye which is the good eye since the brain wants to produce a single and clear image. Naoveruse na yung good eye kaya tinamad / wala ng stimulation yung eye with lower visual acuity
• Strabismic Amblyopia (tropia)

  The good eye is favored it is possible for the eye with lower visual acuity will deviate. Since the brain will neglect the worst eye and cause it to eventually deviate
• Extraocular muscles

  • 4 recti (up, down, medial, lateral)
  • 2 oblique (tortional / rotating)
• Superior rectus

  Moves the eye up
• Inferior rectus

  Moves the eye down
• Lateral rectus

  Moves the eye towards temporal
• Medial rectus

  Moves the eye towards nasal
• Superior oblique


  Muscle is located below, antagonizing or to equal the eye lifting
• Inferior oblique

  Muscle is located above, there should be an opposing muscle to the stimulating muscle, to avoid overshooting the eye
• Amplitude of convergence does not deteriorate with age, unlike accommodation (in presbyopia)
• Certain convergence might be reduced under certain abnormal circumstances (weakening of muscles due to trauma or aging)
• Power of reserve of convergence can be increased by orthoptic exercises
• Orthoptic

  Muscle exercise
• Orthoptists

  People in the visual rehabilitation
• Visual Rehabilitation

  Vision exercises
• Symmetrical convergence

  When the fixated object is situated in the sagittal plane of the head and equal angles are formed with each visual axes and perpendicular line erected midpoint of the line connecting the center of rotation of eyes (baseline)
• Visual axes

  Imaginary line wherein both eyes are fixated on the object of regard (tinitignan ng patient) to the fovea. The light should directly focus on the fovea to have a clear vision
• Center of rotation

  Center point from the behind/ apex of cornea 13.5mm. Pivot (angkla of the eye rotation) of the rotation of the eye
• Baseline

  A combination of the center of rotation of both eyes (left and right eye)
• Asymmetrical convergence

  The point of fixation lies way from the medial plane angle subtended by two visual aces will differ and such convergence will called asymmetrical convergence