Lid lag and lagophthalmos: a clarification of terminology.

Lid lag, lagophthalmos and von Grafe's sign are useful terms which refer to important clinical signs. Despite the fact that they have discrete meanings, they are often used interchangeably and incorrectly by many ophthalmologists and, therefore, their value has been degraded. We provide definitions for these commonly used (but often confused) ophthalmic terms: Lagophthalmos is the inability to completely close the eyes; Lid lag is the static situation in which the eyelid is higher than normal with the globe in downgaze; and von Grafe's sign is a dynamic sign describing the retarded descent of the eyelid during movement of the globe from primary position to downgaze. It is our hope that these terms will be adopted by the ophthalmic community so that precision in definition will lead to clarity of thought and communication.