Eilidh Martin

Backgrounds/Objectives: The aim of this study was to compare differences in the physical characteristics of lissamine green (LG) strips and the outcomes of using different staining techniques. Methods: Two separate complementary investigations were conducted. Physical study: Differences between four LG strips were evaluated in terms of material, dye concentration, and dye absorption. In vivo study: Bulbar conjunctival staining was compared for four application methods of I-DEW LG strips presented in a randomized order for twenty-two participants: (1) single application 5 s after wetting (also repeated using GreenGlo for comparison), (2) single application using two strips held together, 5 s after wetting, (3) two applications using a single LG strip 5 s after wetting, 1 minute apart, (4) the same as method 3, with a single fluorescein strip in between LG applications. White light imaging was performed immediately following application and after 30, 60, 90, and 300 s. Three masked practitioners independently evaluated the randomized staining images for spot count and staining intensity. Results: Physical study: Strip paper fibres demonstrated visible similarities, with no difference in saline absorption (p > 0.05). LG concentration increased as saline retention duration increased (F = 964.1, p < 0.001), and GreenGlo tips were significantly darker (F = 2775.2, p < 0.001). In vivo study: I-DEW application resulted in less conjunctival staining than GreenGlo (p < 0.001). Amongst I-DEW application techniques, staining levels were similar (p > 0.05); however, staining intensity was significantly higher following two applications of I-DEW, 1 min apart, compared to a single application (p = 0.042). Both spot count and staining intensity decreased with time (p < 0.001). Conclusions: Two applications of I-DEW using a single strip, 1 min apart, after wetting with a single drop of saline provided maximal staining. There was also a significant difference in staining intensity observed between LG products.

The concentrations of insulin, leptin, active ghrelin, C-peptide and gastric inhibitory polypeptide (GIP) and their inter-day variations were examined in normal human tears. In addition, correlations between the concentrations of these metabolic proteins and ocular surface parameters were determined. Subjects with healthy ocular surfaces attended three visits, with 7-day intervals. Tear evaporation rate (TER) and non-invasive tear break-up time (NITBUT) were assessed, and a total of 2 µL tears were collected from all subjects. Tear fluid concentrations of insulin, leptin, active ghrelin, C-peptide and GIP were measured by multiplex bead analysis. Insulin was the most highly expressed metabolic protein, followed by leptin, C-peptide, active ghrelin and GIP. Of these, only active ghrelin had a significant inter-day variation (p < 0.05). There was no inter-day variation in the mean concentrations of the other metabolic proteins. Leptin had a strong intra-class reproducibility. No correlation was detected between tear metabolic protein concentrations and ocular surface parameters. This pilot study shows, for the first time, that active ghrelin and GIP are detectable in healthy tears. The strong intra-class reproducibility for leptin shows that it could be used as a potential tear fluid biomarker and, possibly, in determining the effects of metabolic disorders on the ocular surface.