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Microtropia (monofixation syndrome) is a sensorimotor anomaly characterized by a constant small angle esotropia with anomalous correspondence.



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

  1. reduced efficiency and productivity/diminished accuracy/inconsistent work product
  2. diminished performance with time on task
  3. inaccurate/inconsistent depth judgment
  4. pain in or around the eye (ICD: 13)
  5. headaches (ICD: R51)
  6. difficulty sustaining near visual function
  7. avoidance of visually demanding tasks
  8. inaccurate eye-hand coordination
  9. transient blurred vision/illusory movement
  10. transpositions when copying from one source document to another
  11. avoids eye contact
  12. diplopia (ICD: H53.2)/tendency to close or cover one eye/eye turn, deviation(ICD: 9)
  13. abnormal postural adaptation/abnormal working distance (ICD: 3)
  14. spatial disorientation
  15. photophobia (ICD: 149)
  16. inconsistent visual attention/concentration or distractibility while performing visually demanding tasks
  17. general fatigue (ICD: 83)
  18. dizziness/vertigo (ICD: R42); especially during/after sustained visually demanding tasks
  19. motion sickness (ICD: 3XXA)
  20. incoordination/clumsiness (ICD: 8)
  21. asthenopia (ICD: 149)



Microtropia is characterized by one or more of the following diagnostic findings:

  1. small angle strabismus
  2. anomalous correspondence (ICD: 42)
  3. eccentric fixation
  4. central suppression (ICD: 34)
  5. defective stereopsis (ICD: 32)


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



Some cases are successfully managed by the prescription of therapeutic lenses and/or prisms. Most microtropia cases require optometric vision therapy, which incorporates the prescription of specific treatments in order to:

  1. develop adequate fusional vergence ranges, flexibility and stability
  2. enhance accommodative/convergence relationships
  3. integrate binocular function with information processing
  4. integrate binocular skills with accurate motor responses
  5. integrate binocular skills with other sensory skills (vestibular, kinesthetic, tactile, and auditory)
  6. 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. The most commonly encountered microtropia usually requires 30 hours of office
  2. Microtropia may require substantially more office therapy, if complicated by associated factors such as amblyopia, prior eye muscle surgery, cerebral vascular accident, head trauma, and/or 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.