Lateral Orbital Decompression

Abstract

When a volume of fluid or tissue is greater than the space available to contain it, it may overflow the space, lead to increased pressure of the contents of the space, or enlarge the space. Increased pressure of the contents within the space may not be sufficient in the case of a resistant capsule to enlarge the structures, and the pressure may rebound upon the tissue itself, leading to ischemia, fibrosis and atrophy. If the boundaries of space are rigid, as in the skull, help from outside must be obtained to enlarge the space, since the pressure of the tissue within it will not avail. If the encapsulating structures are elastic, as is the case with the scrotum, the space can enlarge with no discernible increase in pressure. The bony orbit will enlarge in response to an increased volume in the early years of life, but after age seven the strength of the bony orbit becomes increasingly greater and less likely to be deformed by intraorbital pressure. Only the base of the orbit or the anterior opening is closed by tissues which have greater elasticity and which may respond to the demand for greater orbital volume. The soft tissues of the orbit offer a site of predilection for the accumulation of fluid, for round cell infiltration, and for diffuse enlargement containing elements of these two mechanisms, as well as chemical changes in the fluid-binding properties of the tissues. At various stages, this increased volume of orbital contents leads to stretching of the elastic tissues at the front of the orbit to increase the volume, followed by increased intraorbital pressure, followed by ischemia of some of the structures which have been subjected to this pressure and which cannot resist it. For these reasons, it is many times desirable to use outside factors to enlarge the orbit to a greater extent than could be brought about by the internal demands of the volume of tissue offered to be contained within the orbit.