Temporal changes in optical quality of air-tear film interface at anterior cornea after blink.

Abstract

To examine temporal changes in the optical quality of the air-tear film interface at the anterior cornea after a blink. Corneal aberrations were determined in fifteen healthy subjects at 1 second time intervals after a blink, up to a total elapsed time of 15 seconds. Corneal aberrations were obtained from corneal elevation maps measured using a Tomey TMS-2N topographer and custom software. All data were decomposed using Zernike polynomials to yield the root mean square (RMS) wavefront deviations, in micrometers, for two pupil diameters (3 and 7 mm). Total wavefront aberration decreased slightly with time in the first few seconds after a blink for both pupil diameters, reaching a minimum after approximately 6 seconds. Thereafter aberrations increased steadily, exceeding the immediate postblink level after approximately 10 seconds. In normal subjects, the contribution of the anterior cornea to the overall ocular aberration remains reasonably stable over the normal interblink interval (approximately 4 seconds) but rises to levels which could perceptibly degrade retinal image quality under circumstances where the interblink interval is increased to exceed 10 seconds, as may occur during the use of visual display screens or when performing difficult tasks.