Orbital Pulleys: a pivot role to understand strabismus

Abstract

Purpose: To review the published literature on the influence of orbital pulleys on oculomotricity and, as such on the etiopathogenesis of different types of strabismus, as well as to clarify the implications for the diagnostic and treatment of these patients. Methods: A comprehensive, internet based, search was performed using the MEDLINE(PubMed) and Web of Science databases selecting articles from 2000 up until December of 2020 using the following Query: (active pulley* OR orbital pulley*) AND (Strabismus* OR Eye movement* OR extraocular muscle*). Results: Some forms of incomitant cyclovertical strabismus, the most common being A and V-patterns strabismus, are associated with one or more heterotopic rectus muscles pulleys, which is observed in children with strabismus in the context of syndromic craniosynostosis and patients diagnosed with superior oblique muscle palsy. Moreover, evidence have been made to suggest that the incomitant strabismus observed in axial high myopia and in the elderly is due to the inferior displacement of horizontal pulleys and degeneration of the lateral rectus-superior rectus muscle band. Conclusions: As pulleys proved to be the mechanical origin of the extraocular muscles, disorders in their location will have an impact on oculomotricity. Clinical observation alone cannot differentiate this aetiology from others so, it is becoming fundamental to perform image exams, for instance orbital magnetic resonance imaging.