ABSTRACT
In normal adults the upper eyelid margin generally rests 2-3 mm below the superior corneal limbus. The lower eyelid margin is usually at or 1 mm above the inferior corneal limbus. In these positions, the vertical interpalpebral fissure measures 8-10 mm. In the presence of eyelid retraction the vertical height of the palpebral fissure is generally wider than normal, and may be as much as 15-18 mm (Fig. 1). This is usually due to an abnormal elevation of the upper lid or a depression of the lower lid. However, even in the presence of significant retraction, the interpalpebral fissure can be within the normal range. For example, in Graves’ disease the lower lid may be retracted with a simultaneous ptosis of the upper eyelid. For this reason, when evaluating eyelid malpositions it is best to measure the eyelid marginal position with respect to the central pupillary reflex or corneal limbus.
I. CAUSES
