The Dry Eye Zone

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Abstract: Wavefront aberrations and lower tear meniscus

Simultaneous measurement of tear film dynamics using wavefront sensor and optical coherence tomography.
Invest Ophthalmol Vis Sci. 2010 Feb 17. [Epub ahead of print]
Koh S, Tung C, Aquavella J, Yadav R, Zavislan J, Yoon G.
University of Rochester Eye institute, Rochester, United States.

PURPOSE: To investigate tear film dynamics using simultaneous measurements of ocular aberrations and lower tear meniscus.

METHODS: Simultaneous measurements of wavefront aberration and lower tear meniscus were performed for 11 normal eyes and 7 eyes with short tear film break-up time dry eye (SBUT dry eye), which have tear film break-up time shorter than 5 seconds, using a wavefront sensor and an anterior segment optical coherence tomography (OCT). During the measurement, the subjects were instructed to blink every 6 seconds for a total of 30 seconds. From the measured aberration, root mean square (RMS) wavefront error and volume modulation transfer function (vMTF) induced by changes in tear film dynamics were calculated for a 5 mm pupil. Lower tear meniscus height (TMH) and area (TMA) were estimated from the cross sectional OCT images of lower tear meniscus.

RESULTS: There was a positive correlation between RMS and tear meniscus dimensions, and a negative correlation was found between the vMTF and tear meniscus in both groups. There was a moderate negative correlation between the post-blink initial RMS change and baseline TMH (R=-0.61) and TMA (R=-0.54) in SBUT dry eyes, which were stronger than in normal eyes. (R= -0.37, R= -0.38)

CONCLUSION: Tear meniscus dimensions increase with RMS over time, and tear quantity before the blink has a significant role in maintaining initial optical integrity, especially in SBUT dry eye. Simultaneous measurement of optical quality and tear meniscus has potential to improve our understanding of tear stability in normal and dry eyes.