Paper-based microfluidic system for tear electrolyte analysis

The analysis of tear constituents at point-of-care settings has a potential for early diagnosis of ocular disorders such as dry eye disease, low-cost screening, and surveillance of at-risk subjects. However, current minimally-invasive rapid tear analysis systems for point-of-care settings have been limited to assessment of osmolarity or inflammatory markers and cannot differentiate between dry eye subclassifications. Here, we demonstrate a portable microfluidic system that allows quantitative analysis of electrolytes in the tear fluid that is suited for point-of-care settings. The microfluidic system consists of a capillary tube for sample collection, a reservoir for sample dilution, and a paper-based microfluidic device for electrolyte analysis. The sensing regions are functionalized with fluorescent crown ethers, o-acetanisidide, and seminaphtorhodafluor that are sensitive to mono- and divalent electrolytes, and their fluorescence outputs are measured with a smartphone readout device. The measured sensitivity values of Na(+), K(+), Ca(2+) ions and pH in artificial tear fluid were matched with the known ion concentrations within the physiological range. The microfluidic system was tested with samples having different ionic concentrations, demonstrating the feasibility for the detection of early-stage dry eye, differential diagnosis of dry eye sub-types, and their severity staging

Changes in corneal structure with continuous wear of High-Dk Soft contact lenses : a pilot study

Despite numerous studies that have considered the effects of extended wear of high-Dk soft contact lenses on ocular physiology, little attention has been paid to the impact of such lenses on central or peripheral corneal thickness and curvature. The present study aims to report the time course of changes in corneal thickness and curvature that accompanies the 30-night continuous wear of new silicone hydrogel soft contact lenses in a neophyte population in a longitudinal study. Methods. Six subjects wore high-Dk lotrafilcon (Dk = 140) on a 30-night replacement schedule for 12 months. Only measurements from the right eye were considered for analysis. Topographical measurements of corneal thickness and curvature were taken. The same parameters were monitored for an additional period of 3 months after lens removal. Results. An almost homogenous increase in corneal radius of curvature was detected for all the locations studied, being statistically significant for the 4-mm cord diameter area. This effect was associated with a progressive thinning effect for the central cornea, whereas midperipheral and peripheral areas did not display such a thinning effect during continuous wear. These effects were still evident for the central cornea 3 months after contact lens wear discontinuation. Conclusions. Continuous wear of high-Dk silicone hydrogel contact lenses is associated with clinically appreciable changes in topographical corneal curvature, whereas only a reduction in corneal thickness is appreciated in the central area. This effect seems to be a result of mechanical pressure induced by these hybrid hyperpermeable materials, characterized by a higher modulus of elasticity. The small sample size compromises the conclusions addressed from this study, and further work will be necessary to confirm the present results.Supported, in part, by MEC (Spain) - PGC under contract PM98-0225

Research on the Stability of a Rabbit Dry Eye Model Induced by Topical Application of the Preservative Benzalkonium Chloride

Dry eye is a common disease worldwide, and animal models are critical for the study of it. At present, there is no research about the stability of the extant animal models, which may have negative implications for previous dry eye studies. In this study, we observed the stability of a rabbit dry eye model induced by the topical benzalkonium chloride (BAC) and determined the valid time of this model.). Decreased levels of mucin-5 subtype AC (MUC5AC), along with histopathological and ultrastructural disorders of the cornea and conjunctiva could be observed in Group BAC-W4 and particularly in Group BAC-W5 until day 21.A stable rabbit dry eye model was induced by topical 0.1% BAC for 5 weeks, and after BAC removal, the signs of dry eye were sustained for 2 weeks (for the mixed type of dry eye) or for at least 3 weeks (for mucin-deficient dry eye)