Abstract
Purpose :
Cationic nanoemulsion were demonstrated to enhance tear film (TF) stability in vivo possibly via long term effects on tear film lipid layer (TFLL). Thus the interaction of Catioprost (CPT), an unpreserved Latanoprost 0.005% cationic nanoemulsion, with meibomian and tear films in vitro and in vivo deserves special study. As CPT contains the cationic agent cetalkonium chloride (CKC) as 0.5 wt% of its oily phase CKC impact on tear constituents was also probed.
Methods :
Human meibum (MGS) and CPT were spread at the air/water interface of a Langmuir surface balance to ensure a range of MGS/CPT oil phase ratios: 20/1, 10/1, 5/1, 3/1, 2/1 and 1/1. The films capability to reorganize during dynamic area changes were evaluated through the surface pressure-area compression/expansion isocycles and film structure was monitored with Brewster Angle microscopy. The layers dilatational rheological properties were probed via the stress relaxation method. The impact of CPT on tear ferning and tear microdroplets evaporation rate was also tested. Identical experiments were performed in presence of pure CKC up to 1 wt% in MGS and tear layers. The effects of cationic nanoemulsions on TF structure and stability at the ocular surface was accessed based on our previously published specular microscopy and keratograph observations.
Results :
The in vitro studies of MGS/CPT layers showed that (i) CPT inclusion (at fixed MGS content) increased film elasticity and thickness and that (ii) CPT can compensate for moderate meibum deficiency. CPT had no impact on tear ferning and moderately (with 25% at 10/1 tear/CPT ratio) delayed tear evaporation rate. In vivo one hour after instillation cationic nanoemusions mixed with TFLL in a manner similar to the interactions in vitro, and resulted in enhanced TFLL thickness and improved TF stability. CKC (at ≤1 wt%) was well tolerated in vitro and had no noticeable impact on MGS and tear properties.
Conclusions :
Under physiologically relevant MGS/CPT ratios CPT interacts favorably with MGS films and enhances their structure and surface properties. The tear/CPT interactions did not affect tear ferning and enhanced tear resistance to evaporation. Similar effects on TFLL and TF were observed in vivo at the ocular surface. In vitro and in vivo data complement each other and facilitated the study of the composition-structure-function relationship that determines the impact of cationic nanoemulsions on TF.
This is a 2020 ARVO Annual Meeting abstract.