Scale and Spatial Distribution of Aberrations Associated with Tear Breakup

Abstract

Purpose We examined the spatial correlation between tear break up (TBU) and the associated optical anomalies on multiple spatial scales. Methods Five subjects refrained from blinking while the time course and patterns of TBU were sequentially observed using fluorescein (FL), retroillumination (RI), and Shack-Hartmann (SH) aberrometry. Wavefront error maps were developed using Zernike polynomials, as well as local zonal analysis of measured wavefront slopes. The difference between these maps reveals the presence of very high order aberrations missed by standard modal fitting methods. Size of SH spots was also quantified to estimate optical perturbations on a microscopic scale. The spatial correlation between TBUand optical aberrations was also computed. Results Degradation of the tear film increased wavefront aberrations over all spatial scales measured. Consistent with tear thinning, blink suppression induced an irregular pattern of phase advances in regions of TBU. SH spot size also increased in regions of TBU, which indicates the presence of optical aberrations on a scale smaller than individual lenslets. Conclusions The optical signature of TBU caused by blink suppression is a combination of wavefront aberrations on macroscopic and microscopic scales due to nonuniform tear film thinning and possible exposure of a rough epithelial surface. Localized optical 2 defects correspond temporally and spatially with TBU revealed by FL and RI. In addition to gross wavefront aberrations, scatter develops in areas of TBU that will further contribute to image degradation and visual disturbances following TBU.

Effects of transient blur and VDT screen luminance changes on eyeblink rate

“…This 13 hypothesis would be in agreement with the high intrusiveness score awarded to the second 14 experimental configuration, in which reflex blinking was elicited by a sudden distortion of the 15 text characters. Indeed, the blinking stimulus behind BE2 may be considered as equivalent to 16 the slight loss of retinal image quality resulting from tear film instability and breakup [29,30] It is interesting to note that the inclusion of a 20 ms white screen in front of the text did not 20 lead to a significant increase in SEBR, if unaccompanied by explicit blinking instructions. This 21 finding was unexpected, as the short presentation of a white screen was believed to be able to 22 benefit from both strategic approaches described above.…”

Experimental investigation of accommodation in eyes fit with multifocal contact lenses using a clinical auto‐refractor

“…In addition to the Shack‐Hartmann (COAS) aberrometer on‐eye measures of refractive state made with the clinical aberrometer, ex vivo maps of contact lens wavefront error and optical power were measured using a single‐pass aberrometer with a Shack‐Hartmann wavefront sensor and a sampling resolution of 0.104 mm (ClearWave, http://www.lumetrics.com). To capture the abruptly changing optical properties across the multifocal and zonal bifocal lenses, a zonal (local integration) method was used to reconstruct the ex vivo wavefronts …”

Effects of tear film dynamics on quality of vision

“…Thus, there is difficulty in detecting tear film-induced alterations in HOAs, when using commercially available wavefront sensors. Recently, the formation of scatter-producing microaberrations associated with tear film breakup was reported; these are too fine to be resolved with a clinical Hartmann-Shack wavefront sensor 33. Measurement of wavefront aberrations on a microscopic scale would help in clarifying wavefront variations for detecting breakup patterns.…”