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myectomy

Myectomy is a weakening procedure, one of the strabismus operations that decrease the pull of an extraocular muscle.1 In the technique described for the inferior oblique, the surgeon clamps the muscle with two hemostats about 8 mm apart and excises the segment between the clamps.2 Some texts use the term for detaching a muscle from its insertion without reattaching it, the same operation as a disinsertion.1,3

Myectomy is most commonly used to weaken an overacting inferior oblique muscle, and only very occasionally on a severely contracted rectus muscle.1,3 An inferior oblique myectomy can reduce the hyperdeviation in the field of action of that muscle and in primary position.2 Weakening the inferior oblique also tends to reduce or eliminate the excyclotropia that accompanies its overaction, while the effect on horizontal alignment in primary position is negligible.2

More detail

The average reduction of a hyperdeviation by inferior oblique myectomy is 11.5°, and the effect increases with the size of the preoperative deviation.2 If a tight inferior oblique has impeded the superior oblique, superior oblique function may improve after the operation.2 A unilateral inferior oblique weakening procedure should be done only after the surgeon confirms that elevation of the adducted fellow eye is normal, because otherwise the unoperated eye becomes hypertropic.2 Overcorrection is rare and tends to occur when the operated muscle was acting normally or the upshoot in adduction was minimal.2

Sources (17)
  1. Pickwell's Binocular Vision Anomalies, ch. 17
  2. von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 26
  3. Kanski, Clinical Ophthalmology (2024), ch. 18
  4. Agarwal, S. (2020). Strabismus Surgery. In: Agarwal, S. (ed.) Strabismus Simplified. Springer, Singapore. https://doi.org/10.1007/978-981-15-2135-0_9
  5. Kushner, B.J. (2017). Strabismus. In: Olitsky, S.E. (ed.) Pediatric Ophthalmology. Springer, Cham. https://doi.org/10.1007/978-3-319-28315-5_10
  6. Raina, U.K., Tiwari, H.K., Sood, G.C. and Raj, S. (2004). Inferior oblique myectomy for superior oblique palsy. Journal of Pediatric Ophthalmology and Strabismus, 41(2), pp.86-88.
  7. von Noorden, G. and Campos, E. (2002). Binocular Vision and Ocular Motility. 6th ed. St. Louis: Mosby.
  8. PubMed Central: PMC5519270
  9. Nature: 6700488
  10. EyeWiki: Strabismus_Surgery,_Cyclovertical
  11. EyeWiki: Inferior_Oblique_Surgeries
  12. PubMed Central: PMC4502171
  13. PubMed Central: PMC8126736
  14. ScienceDirect: muscle-resection
  15. American Academy of Ophthalmology: strabismus-surgery-inferior-oblique-myectomy
  16. ScienceDirect: S1572100023000121
  17. ScienceDirect: strabismus-surgery

Reviewed October 2026

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