Dynamic changes in the tear film in dry eyes

PURPOSE. To examine the dynamics of the tear film in patients with dry eye by measuring the wavefront aberrations of the anterior surface of the film. METHODS. Anterior surface aberrations for a 7-mm pupil were determined in 13 patients with dry eye at 1-second time intervals, for 15 seconds after a blink. The aberrations were calculated from the elevations provided by corneal topography. All data were decomposed using Zernike polynomials. Total, spherical, and comalike aberrations terms were studied separately. Results were compared with those in normal eyes. Outcome measures included comparison with clinical tear breakup time measurements. RESULTS. The total root mean square ( RMS) wavefront aberration in patients with dry eye passed through in a minimum of 2.9 +/- 0.4 seconds after a blink in comparison to the minimum at 6.1 +/- 0.5 seconds in normal patients. In both groups, the minimum in total aberration appeared to be associated with similar changes in comalike aberrations, rather than in spherical aberrations, which increased monotonically with time. The time at which minimum RMS aberration occurred correlated reasonably well with the measured tear breakup times. CONCLUSIONS. Measurements of the dynamic changes in the optical aberrations introduced by the anterior tear film surface give valuable insights into tear film changes and may provide a convenient objective method for the diagnosis of dry eye.