Abstract

Background: Tear fluid analysis contributes to the greater understanding of various ocular and systemic diseases. Obtaining adequate samples for tear analysis requires an effective collection method. The direct aspiration method using capillary micropipette may be challenging to the operator and patients especially when collecting non stimulated tear samples. The purpose of this study is to assess efficacy of polyvinyl alcohol (PVA) foam and polyester wick (PW) for non-stimulated tear sample collection. Methods: Thirty subjects participated in the first part of the study to quantify tear volume in seconds using PVA foam (Microstaar foam tip plunger, Staar Surgical) and PW (Transorb Wick, Filtrona). Tear volume absorbed (VA), volume recovered (VR) and recovery ratio (RR) were determined. Tear protein analysis included major protein profile and total protein concentration (TPC). Twelve subjects participated in the second part of the study to quantify lysozyme, lactoferrin, IgA and serum albumin by enzyme-linked immunosorbent assay (ELISA) technique from tears collected from PVA and PW for 3 minutes. Results: Ninety samples were collected (PVA = 45, PW = 45) for first part of the study. VA by PVA (6.80 ± 1.29 μL) and PW (6.44 ± 1.36 μL) were comparable (p = 0.267) whereas VR from PVA (3.89 ± 1.12 μL) was less compared to PW (5.66 ± 1.35 μL, p = 0.051). RR from PVA was significantly less than in PW (29% vs. 67%, p < 0.001). Mean TPC analyzed from 12 PVA samples (16.90 ± 2.72 mg/mL) and 21 PW samples (16.60 ± 2.02 mg/mL) were comparable (p = 0.674). Major tear proteins profiles (79 kDa, 27 kDa, and 18-14 kDa) were identical regardless of collection material used. Lysozyme, lactoferrin, IgA and serum albumin detected by ELISA were from 6 PVA samples (0.26 ± 0.03 mg/mL, 9.80 ± 3.13 mg/mL, 0.88 ± 0.15 mg/mL and 0.88 ± 0.33, 113 respectively) and 9 PW samples (0.30 ± 0.01 mg/mL, 11.62 ± 2.07 mg/mL, 1.10 ± 0.73 mg/mL and 0.88 ± 0.25 mg/mL, respectively) were comparable. Conclusion: Both PVA and PW showed similar ability to absorb tear fluid but PVA was less efficient in tear fluid recovery.

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