Eyelid pressure: inferences from corneal topographic changes.

Area of Science:

• Ophthalmology
• Biomechanics
• Corneal Physiology

Background:

• Eyelid pressure is known to influence the corneal surface.
• The precise distribution, contact area, and biomechanics of eyelid pressure on the cornea remain largely uncharacterized.
• Direct measurement of these factors is challenging, necessitating indirect analysis.

Purpose of the Study:

• To infer the distribution and biomechanics of eyelid pressure on the cornea.
• To investigate the relationship between eyelid morphometry and corneal topographic changes.
• To identify the primary site of eyelid-cornea contact.

Main Methods:

• Corneal topography was measured in 18 healthy subjects (19-29 years) under varying conditions.
• Conditions included two downward gaze angles (20 and 40 degrees) and two visual tasks (reading, steady fixation).
• Digital photography captured Marx line width, a proxy for eyelid contact area.

Main Results:

• Corneal changes were significantly greater at 40-degree downward gaze compared to 20 degrees (P < 0.001).
• Lower eyelid-induced corneal changes exceeded upper eyelid changes at 40-degree gaze (P < 0.01).
• Upper eyelid Marx line width correlated with the magnitude of corneal change (R = 0.32, P < 0.05).

Conclusions:

• Corneal topographic analysis provides insights into upper and lower eyelid pressure dynamics.
• Increased downward gaze elevates upper eyelid pressure.
• Lower eyelid pressure surpasses upper eyelid pressure at 40-degree downward gaze, with Marx line evidence supporting its role in eyelid-cornea contact.