A Case of Globe Subluxation
BY WILLIAM L. MILLER, OD, PHD, FAAO
We saw a patient in the clinical service recently who upon dilation drop application had an "eye-popping" experience. She exhibited an uncommon and disconcerting clinical entity known as globe subluxation, sometimes referred to as globe luxation, which occurs when the equator of the globe passes anterior to the palpebral aperture. The anxious patient will typically experience a blepharospasm, which further complicates returning the globe to its position within the orbit.
Etiology and Risk Factors
Three categories generally explain the etiology of globe subluxation. The most common is spontaneous, which occurs in about 73 percent of patients and is without any precipitating event or conscious effort. However, this may be a misnomer because triggering events can lead to a spontaneous globe subluxation. The most common trigger reported is lid manipulation such as what occurs during contact lens application, tonometry, exophthalmometry, indirect fundoscopy, foreign body removal and, in our case, drop instillation. Another trigger may be associated with any sort of valsalva maneuver. The most common risk factor for spontaneous globe subluxation is exophthalmos (81 percent).
The second category is voluntary, poignantly illustrated in a report of an obsessive compulsive patient who habitually and continually subluxated his globe (Apostolopoulos 2004).
Traumatic globe subluxation represents the final category and, as the name implies, is secondary to ocular trauma.
In some cases, advising patients to have their thyroid levels checked may be warranted when they exhibit proptosis along with other pertinent case history findings. Orbital decompression may be indicated in cases of a thyroid orbitopathy with resultant proptosis.
Managing Globe Subluxation
The immediate danger in a globe subluxation is exposure keratitis from ocular surface desiccation. Use topical tear supplements, as increased desiccation only magnifies the resultant blepharospasm, exacerbating the vicious cycle. Some recommend topical drops of anesthetic to decrease the sensation and allow the blepharospasm to subside; in some more severe cases a facial block may be necessary to cause paresthesia of the orbicularis oculi muscle and allow for globe repositioning.
Other complications may include corneal abrasions, blurred vision and pain. If the subluxation is left untreated or happens regularly, the patient may also develop an optic neuropathy. Any axial globe displacement greater than 10mm may cause a tethering of the optic nerve.
The most immediate and direct path to alleviating a globe subluxation is to help the patient relax. Recline the patient to allow the forces of gravity to reposition the globe. Hold the eyelids open and gently apply digital pressure to the sclera near the limbal border. Don't apply too much pressure because this will cause extreme discomfort. As the stress level decreases and slight pressure is placed on the globe, it will recede back into the normal orbit behind the palpebral aperture. Tse (2000) suggested that the patient look downward while the upper eyelid is pulled upward and the globe is depressed with the index finger of the contralateral hand. He also suggests that you anesthetize the ocular surface and use a pediatric Desmarres retractor or paper clip (spread at a right angle) positioned under the upper lid at the location of the superior rectus to allow the globe to move past the stretched eyelid.
After the event, instruct the patient as to why this may have occurred and what to do if it recurs. A visual field assessment may be necessary to rule out any traumatic optic neuropathy. CLS
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Dr. Miller is the Director, Cornea and Contact Lens Service at the University of Houston College of Optometry. He is a member of the American Optometric Association and serves on its Journal Review Board. You can reach him at firstname.lastname@example.org.