Correlation between the aqueous tear clearance and the turnover of tear lipids in dry eye patients

Purpose: To determine by anterior segment spectral domain optical coherence tomography (OCT) the turnover of tear lipids in patients with aqueous tear deficient dry eyes (ATD) and its correlation with the aqueous tear clearance. Methods: Eighty-two adult patients presenting with complaints of ocular irritation were evaluated for abnormalities of ocular surface in the same sequence. It included clinical history, a symptom questionnaire (OSDI = Ocular Surface Disease Index), fluorescein tear break-up time (FTBUT), fluorescein staining of the cornea and conjunctiva graded according to the Oxford system (FSOS), standardized visual scale (SVST), Schirmer I test, and a slit lamp examination of the lid margins and meibomian glands. T A lipid-based artificial tear (LAT) was used as a tracer to obtain an enhanced OCT imaging of the lower tear meniscus (LTM) and to determine the clearance of tear lipids (CTL). Results: The correlations between CTL and OSDI, FTBUT, FSOS, Schirmer test scores, were found to be statistically significant (p<0.001, Spearman correlation coefficient was 0.79, -0.68, 0.58, -0.5 -0.43, respectively). Moreover, also a significant relationship between CTL and the aqueous tear clearance (SVST) was observed (Spearman correlation coefficient was 0.68, p<0.001). Conclusions: The results obtained with this new technique of contrast-enhanced OCT imaging of the ocular surface are in agreement with other classical tear tests. The reduced dynamics of tear lipids was associated with a slow aqueous tear clearance. This new finding could lead to a better understanding of the complex pathogenesis of dry eye syndrome and of its alterations.