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Simultaneous Vision without Fusion


Simultaneous vision without fusion is a cortical, visual phenomenon existing in the absence of correspondence between the two visual channels coupled with the absence of suppression.



The signs and symptoms associated with simultaneous vision without fusion may include, but are not limited to, the following:

  1. diplopia (ICD: 2)
  2. strabismus (horizontal, vertical, or cyclo)
  3. inaccurate/inconsistent depth judgment
  4. inaccurate eye-hand coordination
  5. spatial distortions and faulty localization
  6. asthenopia (ICD:H53.149)
  7. inconsistent visual attention/concentration and/or awareness
  8. headache (ICD: R51)
  9. general fatigue (ICD: 83)
  10. reduced efficiency and productivity
  11. motion sickness (ICD: 3XXA)
  12. incoordination/clumsiness (ICD: 8)
  13. faulty visual information processing
  14. blur



Simultaneous vision without fusion has one or more of the following diagnostic findings:

  1. diplopia, visual confusion, defective stereopsis
  2. strabismus, aniseikonia, and/or anisometropia
  3. active avoidance of bifoveal stimulation which may be accompanied by rapid changes in deviation or conjugate eye movements
  4. inability to alleviate diplopia with prism neutralization and/or target alignment in instrument


The doctor of optometry determines appropriate diagnostic and therapeutic modalities, and frequency of evaluation and follow-up, based on the urgency and nature of the patient’s conditions and unique needs. Vision disorders that are not totally cured through vision therapy may still be ameliorated with significant improvement in visual function and quality of life. The management of the case and duration of treatment would be affected by:

  1. the severity of symptoms and diagnostic factors, including onset and duration of the problem
  2. the complications of associated visual conditions
  3. implications of patient’s general health, cognitive development, physical development, and effects of medications taken
  4. etiological factors
  5. extent of visual demands placed upon the individual
  6. patient compliance and involvement in the prescribed therapy regimen
  7. type, scope, and results of prior interventions as well as etiological factors



Simultaneous vision without fusion usually accompanies a binocular anomaly such as strabismus. Optometric vision therapy is required for effective treatment of simultaneous vision without fusion and incorporates the prescription of specific treatments in order to:

  1. establish normal correspondence and fusion
  2. establish sensorimotor binocular alignment
  3. normalize vergence, accommodative, and stereoscopic responses
  4. integrate binocular and oculomotor skills
  5. increase binocular endurance and stamina
  6. integrate visual skills with higher level information processing



The following treatment ranges are provided as a guide. Treatment duration will depend upon the particular patient’s condition and associated factors. When duration of treatment beyond these ranges is required, documentation of the medical necessity for additional treatment services may be warranted for third-party claims processing and review purposes.

  1. Full treatment of simultaneous vision without fusion requires resolution of associated
  2. The complication of simultaneous vision without fusion in association with constant exotropia can add an additional 32-46 hours of office therapy to the strabismus
  3. The complication of simultaneous vision without fusion in association with constant esotropia can add an additional 36-52 hours of office therapy to the strabismus
  4. Associated conditions such as head trauma, stroke, and systemic conditions may add substantially to the therapy



At the conclusion of the active treatment regimen, periodic follow-up evaluation is required. Should signs, symptoms, or other diagnostic factors recur, further therapy may be medically necessary.

Therapeutic lenses may be prescribed during or at the conclusion of active vision therapy to assist in the maintenance of long-term stability.