Quantification of the tear film lipid layer using optical coherence tomography.

Abstract

Purpose : To quantify the tear film lipid layer (TFLL) noninvasively using an ultrahigh-resolution optical coherence tomography (OCT) and a novel post-processing algorithm and to measure its changes after instillation of a lipid-containing lubricating emulsion (Cationorm, Santen Pharmaceutical).

Methods : An ultrahigh-resolution OCT system with a theoretical axial resolution of 1.2 μm in tissue was used for imaging of the TFLL. After baseline measurement, each of the 20 subjects in the control group received one drop of Hydrabak (0.9% NaCl solution). Each of the 10 healthy subjects in the study group received one drop of Cationorm. OCT-based TFLL quantity was determined using the air-tear reflectivity map of the central cornea and a novel algorithm (TFLL_OCT). TFLL thickness was also measured using a commercially available system (Lipiview, TearScience Inc.) based on white-light interferometry (TFLL_WLI).

Results : OCT-based TFLL_OCT quantity increased on average by 34 % after administration of Cationorm (Fig. 2). The maximum increase (60.8% ± 28%) occurred after 30 minutes. In the control group, OCT-based TFLL quantity measurements revealed an average increase of 7.2% (cf. Fig. 2) over all measurement time points after instillation of Hydrabak. The average inter-volume coefficient of variation of the OCT-based TFLL quantity value was 13.9%. TFLL_WLI thickness measurements using the Lipiview system yielded an average increase of 17.6% in the study group.

Conclusions : An OCT-based approach for determination of the TFLL quantity was reported. This method could be used to study the role of the lipid layer in the formation of a stable tear film and its influence on the evaporation rate. Furthermore, it has the potential to be used in clinical settings investigating dry eye diseases and for testing efficacy of lipid-based dry eye treatments.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Fig. 1. OCT-based determination of the TFLL quantity using reflectance maps of the air-tear interface. (A) Model of the pre-corneal tear film and its corresponding OCT signal. (B-D) Representative air-tear interface reflectivity maps. (E) Model-based quantification of the TFLL thickness.

 

Fig. 2. Relative change of TFLL in comparison to baseline after instillation of (A) Cationorm (B) Hydrabak (control). Data are presented as mean change ± SD.