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. 2009 Nov;93(11):1535-8.
doi: 10.1136/bjo.2008.156828. Epub 2009 Aug 18.

Turnover rate of tear-film lipid layer determined by fluorophotometry

H Mochizuki  1 , M Yamada, S Hatou, K Tsubota
Affiliations

Turnover rate of tear-film lipid layer determined by fluorophotometry

H Mochizuki et al. Br J Ophthalmol. 2009 Nov.

Abstract

Aim: This study was performed to independently assess the turnover rates of aqueous and lipid layers of the tear film.

Methods: Two fluorescent dyes, fluorescein sodium and 5-dodecanoylaminofluorescein (DAF), which is a free-fatty-acid conjugate of fluorescein, were applied to the right eye of 12 healthy volunteers. Fluorescent intensity of the precorneal tear film was measured at the central cornea every minute for 10 min for fluorescein sodium, and every 5 min for 50 min for DAF. The turnover rate was calculated by plotting fluorescent intensity against time in a semilog plot and expressed as %/min.

Results: Turnover rates of fluorescein sodium and DAF were 10.3 (SD 3.7)%/min and 0.93 (0.36)%/min, respectively. The turnover rate of DAF was significantly lower than that of fluorescein sodium (p<0.05, Mann-Whitney test). The turnover rate of DAF positively correlated with that of fluorescein sodium (r = 0.93, p<0.05).

Conclusion: Our results indicate that the turnover of lipids in tears is much slower than the aqueous flow of tears, and that this lipid turnover is associated with the aqueous flow of tears in healthy adults.

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Conflict of interest statement

Competing interests: None.

Figures

Figure 1
Figure 1
Fluorescein sodium (A) and 5-dodecanoylaminofluorescein (DAF) (B) after a modified Bligh and Dyer procedure. The fluorescent yellowish colour of fluorescein sodium was seen in the upper aqueous layer, whereas the dye colour of DAF was seen in the lower lipid layer.
Figure 2
Figure 2
Plot of fluorescence intensity and 5-dodecanoylaminofluorescein (DAF) concentration. The relationship between fluorescence intensity and DAF concentration was linear (r2 = 0.991).
Figure 3
Figure 3
Representative result of turnover rate obtained from one subject. Fluorescence intensity of 5-dodecanoylaminofluorescein (black circle) decayed with time at a flow rate of 1.14%/min, which was lower than that of fluorescein sodium (14.5%/min; white circle).
Figure 4
Figure 4
Relationship between the turnover rates of 5-dodecanoylaminofluorescein (DAF) and fluorescein sodium. The DAF turnover rate positively correlated with that of fluorescein sodium (r2 = 0.87, p<0.05).
See this image and copyright information in PMC

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