Dynamic wavefront aberrations and visual acuity in normal and dry eyes

Purpose: The aim was to study the dynamic properties of wavefront aberrations and visual acuity in normal and dry eyes. Methods: Thirty dry-eye patients and 27 normal subjects participated in this study. Multi-file mode of a Hartmann-Shack wavefront sensor was used to measure dynamic wavefront aberrations for a period of 45 seconds. Dynamic measurements of visual acuity (VA) were made for 150 seconds using a multi-functional VA tester. Standard deviation of the measurements (RMS or VA) over the testing period was used to estimate instability of the dynamic wavefront aberration and VA. Results: For most subjects, both wavefront aberration and VA changed over time and the instability varied substantially among individuals. Blink-dependent fluctuation in wavefront aberration or VA was observed for sonic dry-eye subjects. On average, the dry-eye group had greater instability than the normal group in either the higher order wavefront aberrations (t = 2.09, p = 0.03, for OD; t = 3.76, p = 0.001, for OS) or the VA (t = 2.09, p = 0.02, for OD; t = 204, p = 0.03, for OS). Instability of VA in the dry-eye group was significantly correlated with blink rate (r = 0.28, p = 0.02). Conclusion: Dynamic changes in wavefront aberrations and VA are highly individual dependent, while the dry eye lends to be less stable than the normal eye. The results suggest that tear-film fluctuation might play a role in determining dynamic wavefront aberration and VA, however, contributions from other factors should not be overlooked. For dry eye, dynamic change in VA depends on blink rate.