It is a well known fact that when progressive inflammatory conditions of the tear sac advance sufficiently to change the normal contour of the region of the internal canthus, the swelling (phlegmon or mucocele) or fistula is always to be found below the horizontal axis of the eye (fig. 1). Even in phlegmonous cases in which the inflammation may extend above the eye the greater part of the swelling is always distinctly beneath the horizontal axis. In the literature, however, I find no exact explanation of this clinical fact, although it is constantly made use of in differentiating fistulas of the ethmoid and frontal sinuses from those of the lacrimal sac. Lacrimal fistulas perforate below the horizontal orbital axis, while fistulas of the frontal and ethmoid sinuses appear above this axis.
An abscess always advances along the path of least resistance, and just as a psoas abscess follows the lumbar muscles, so there is a definite anatomic reason for inflammations of the lacrimal sac pointing below the horizontal axis of the eye.
West JM. WHY DO LACRIMAL FISTULAS, PHLEGMONS AND MUCOCELES ALWAYS APPEAR BELOW THE HORIZONTAL AXIS OF THE EYE? Arch Ophthalmol. 1932;7(5):775–778. doi:10.1001/archopht.1932.00820120127011
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