Discussion
hyperkeratinization, HOA, disorders of the tear film [, Obstruction of meibomian ducts
PATHOGENESIS, CORNEA
Previous studies have shown that HOA not only occur because of irregularities of the cornea, but also because of disorders of the tear film [Our study showed that LLT and HOA increase immediately after application of a cationic nanoemulsion of lipids (CN), although no correlation was found between the two parameters. Application of the lipophilic semifluorinated alkane (SFA), F6H8, did not increase the LLT. The increase of LLT shortly after application of CN is in accordance with literature [By contrast, F6H8 did not increase of HOA immediately after application. Agarwal et al. used a high-speed camera to visualize the impact of F6H8 on the tear film surface [Obstruction of meibomian ducts, hyperkeratinization and increased viscosity are major drivers in the pathogenesis of MGD [Considering the significant improvement of LLT, it is still surprising that we could not measure any change in aberrations. Montés-Micó et al. postulated that the lack of tears does not necessarily lead to higher aberrations in DED [F6H8 and CN increased the tear-break-up time (TBUT), which is in line with literature [There are limitations to our study. First, the integrity and stability of the tear film are dependent on many factors, including exogenous ones. The tear film is influenced by the sequence of examinations (which was standardized in our study), weather [Second, different devices for measuring HOA can only be compared to a limited extent. In a study that compared several aberrometers, the Visual Function Analyzer (Tracey Technologies, Houston Texas, USA) deviated significantly from other aberrometers in measuring the RMS values [Third, in cohort B the control group consisted of healthy individuals without DED, with a higher (i.e. normal) lipid layer thickness of > 75 ICU. While this limits comparison of the three groups at baseline, it also helped to demonstrate that F6H8 leads to normalization of the LLT.Fourth, the presented results are based on this specific population, and future studies (on other populations) are warranted to justify the hypothesis.In conclusion, the significant change in the lipid layer of the tear film caused by application of the lipid-based tear supplements studied, had no influence on higher-order aberrations in short- and long-term applications and thus should not have a negative impact on visual quality.