Factors influencing lid pressure on the cornea.

Purpose: To investigate the effects of eyelid pressure on corneal topography in different angles of gaze and under different eye movement conditions.

Methods: Ten young subjects with healthy eyes were recruited for the study. Corneal topography of the right eye was measured with a videokeratoscope before and after four 15-minute visual tasks (downward gaze of 25 degrees or 45 degrees , both with no eye movements or 1 Hz eye movements). The four tasks were conducted on four separate mornings. RESULTS.: All subjects showed significant regions of topographic change after each of the four tasks. In general, eye movements were found to cause greater topographic changes than tasks without eye movements, and the larger angle of downward gaze led to greater changes in topography. The topographic changes were located close to the lid margin position during each task.

Conclusions: The pressure exerted by the eyelid is capable of altering corneal topography. These changes are enhanced when the eye looks downward and when the eye moves laterally.