‘Bugging-out’ of an eyeball is called exophthalmos. As the eye comes forward it forces the eyelids apart and causes a staring appearance.
Exophthalmos is caused by an increase in the bulk of the contents of the bony eye cavern (orbit) behind the eye. This occurs most commonly as a result of an immune system disorder associated with the thyroid gland.
In this case, the protrusion is caused by enlargement of the small eye-moving muscles behind the globe as a result of the presence of antibodies (immunoglobulins) and an accumulation of white cells (lymphocytes) and fluid.
Dysthyroid exophthalmos does not necessarily occur at the same time as the active thyroid gland malfunction. The protrusion may occur months or even years after a thyroid upset, or may even on occasions precede it.
Persistent and disfiguring exophthalmos may be treated by removing the bony floors of the eye sockets or be reinforcing the lids with mersilene mesh implants (mersilene is a tough plastic that the body tolerates well).
Although thyroid problems are by far the most common cause of exophthalmos, even if only one eye appears to be affected, protrusion of an eye-ball may be caused by the presence of other material in the orbit, such as a mucus-filled cyst (mucocele), or cancer.
It should always be regarded as a potentially grave sign, and should never be ignored.
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