Luxation of the globe is a rare event whereby the eyelids slip behind the midcoronal plane of the eye in an extremely proptotic eye (Figures 195-1 and 195-2). Subsequent spasm of the orbicularis oculi muscle maintains the luxation of the globe. Extraocular eye movements become severely limited. The optic nerve and retinal vasculature are subjected to an abnormal amount of traction which results in possible damage to these structures or the retina.1 This can result in partial or full blindness of the affected eye if it is not reduced before onset of irreversible ischemic changes.
Globe luxations. A. Spontaneous luxation. Note the eyelids behind the midcoronal plane of the eye and the lacrimal gland in front of the eyelids. (Used with permission from www.clinicalgate.com.) B. Voluntary luxation. C. Luxation associated with forceps delivery. (Used with permission from reference 16.)
The luxated globe. A. Superior view. B. Lateral view.
ANATOMY AND PATHOPHYSIOLOGY
There are three major causes of globe luxation: spontaneous, voluntary, and traumatic. Spontaneous luxation tends to occur in individuals with shallow orbits (Figure 195-1A).2 Structural abnormalities (e.g., anomalous extraocular muscles, laxity of the supporting fascia, and laxity of the supporting muscles) can predispose to spontaneous luxation.2-4 Pathologic processes that can cause proptosis can predispose to luxation. The literature documents cases of luxation associated with cerebral gummas, chronic obstructive pulmonary disease, craniofacial dysostosis, Cushing’s syndrome, floppy eyelid syndrome, Graves’ disease, histiocytosis X, and orbital tumors.1,5-9 Voluntary luxation occurs in individuals who learn to cause globe propulsion by using a digit or their extraocular muscles (Figure 195-1B). Some patients use a Valsalva maneuver to luxate their globe(s) voluntarily.
Traumatic luxation results from injury to the globe or the surrounding bony orbit.10,11 It can occur from motor vehicle accidents or relatively minor trauma to the face.12,13 Traumatic luxation can be associated with complete avulsion of the optic nerve. Traumatic luxation can occur from intentional eye gouging or during the forceps-assisted delivery of a neonate (Figure 195-1C).14-16
The normal anatomic relationship of the globe to the surrounding structures is seen in Figure 195-3. The midcoronal plane of the globe is through the widest portion of the eye and divides it into anterior and posterior halves. The eyelids get behind the midcoronal plane of subluxed globes, the orbicularis oculi muscle is pulled taut, and the orbicularis oculi muscle begins to go into spasm. This spasm prevents spontaneous reduction of the eye.