Orbital and Periorbital Disease Causing Mechanical Strabismus

The ocular adnexa, orbital structures and paranasal sinus and associated diseases can mechanically impair eye movements though a variety of different mechanisms. These conditions can both physically prevent the eye from moving to a certain position, and can limit eye movement by entrapping or impairing the movement of an eye muscle. In addition, these same processes can impair eye movements through direct effect on cranial nerves 3,4 and 6. These clinical presentations will generally be identified based on the circumstances of the patients presentation and the associated orbital symptoms and signs that usually accompany their presentation. Conditions generally fall into four broad categories: 1) infections and tumors of the orbit or paranasal sinuses 2) inflammatory conditions affecting the orbit 3) trauma to the orbital bones and 4) iatrogenic in association with surgery of the paranasal sinuses. The most common scenarios are processes that affect the paranasal sinuses and then either extend into the orbit or otherwise affect orbital bones, eye muscles or soft tissues (orbital fractures). Other common scenarios for mechanical strabismus include processes that infiltrate the orbital fat and connective tissue or affect the trochlear.