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Fusion with Defective Stereopsis


The sensory anomaly referred to as defective stereopsis is characterized by an inability to accurately and rapidly process, recognize, and respond to binocular disparity.


The signs and symptoms associated with defective stereopsis may include, but are not limited to, the following:

  1. diplopia (ICD: H53.2), intermittent
  2. eye turn/deviation (ICD:H51.9)
  3. inaccurate/inconsistent depth judgment
  4. inaccurate eye-hand coordination
  5. tendency to cover/close one eye
  6. spatial disorientation
  7. abnormal postural adaptation/abnormal working distance (ICD: R29.3)
  8. asthenopia (ICD: H53.149)
  9. inconsistent visual attention/concentration or distractibility while performing visually demanding tasks
  10. general fatigue (ICD: R53.83)
  11. avoidance of visually demanding tasks
  12. motion sickness (ICD: T75.3XXA)
  13. incoordination/clumsiness (ICD: R27.8)
  14. dizziness/vertigo (ICD: R42); especially during/after sustained visually demanding tasks


Defective stereopsis has one or more of the following diagnostic findings:

  1. difficulty perceiving crossed and/or uncrossed disparity
  2. inconsistent or delayed responses to stereoscopic stimuli
  3. difficulty accurately responding to stereoscopic stimuli as vergence and/or accommodative demands vary.



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
  8. occupational/avocational goals


Defective stereopsis usually accompanies a binocular anomaly. Optometric vision therapy is required for effective treatment of defective stereopsis and incorporates the prescription of specific treatments in order to:

  1. enhance processing of stereoscopic visual information
  2. increase the speed and accuracy of responses based on stereoscopic information
  3. integrate stereoscopic responses with vergence and accommodative demands
  4. integrate stereoscopic processing with motor responses
  5. increase visual stamina/integrate newly established skills with 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. Defective stereopsis is not an independently treated condition, but a complication adding to the treatment hours of associated conditions. Full treatment requires resolution of associated visual
  2. The complication of defective stereopsis usually requires 12 hours of office therapy.
  3. Fusion with defective stereopsis may require substantially more office therapy, if complicated by associated conditions such as cerebral vascular accident, head trauma, and/or other systemic conditions.


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.