Method of manufacturing a tear flow measurement device
Inventors
Tai, Yu-Chong • Scianmarello, Nicholas E. • Humayun, Mark S.
Assignees
California Institute of Technology • University of Southern California USC
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Publication Number
US-12239374-B2
Publication Date
2025-03-04
Expiration Date
Abstract
A lacrimal tear flow measurement device, and methods of manufacture and use, are described that includes a polymer microcapillary tube or similar structure having at least one end coated on the outside with soft silicone rubber and one end treated on the inside to be hydrophobic. The hydrophobic end keeps liquid from escaping or entering that end while allowing air to pass. The rest of the tube's insides may be hydrophilic or a neutral hydrophobe. As a Schirmer's test strip replacement, the entrance end of the device can be touched to the lacrimal lake of a patient's eye to collect suck up, or merely collect, tear fluid within the collection tube for weighing, volume measurement, or other analysis. Long-term collection devices for wear between doctors' visits can have a bypass channel allowing liquid to flow back onto the eye.
Core Innovation
A tear secretion measurement device includes a polymer microcapillary tube with an inner surface whose wetting properties are localized. The inner surface is hydrophobic in a region near an exit end configured to prevent tear liquid escape while allowing air passage, and the inner surface is hydrophilic or neutral hydrophilic along the remainder of the microcapillary to permit tear liquid uptake.
The device includes an entrance end for contact with the lacrimal lake and may function as a Schirmer-strip replacement for short-term collection. Tear amount can be measured by weighing or by volume, and tear liquid can be analyzed by liquid chromatography.
For long-term wear, the polymer microcapillary can include a bypass channel configured to allow excess fluid to return to the eye. The microcapillary may be straight, curved, or coiled, and the coil has an inner diameter in a specified range; it can also be provided as a sclera-lens reservoir.
Claims Coverage
The independent claims cover three main inventive manufacturing aspects: localized hydrophobic inner-surface treatment near the exit end, localized hydrophobic inner-surface treatment defined by a length fraction from the exit end, and hydrophobic treatment combined with winding the polymer capillary tube into a coil with a specified coil inner diameter. Across the independent claims, inventive features are built around localized inner-surface wettability control and specific structural arrangements of the polymer capillary tube.
Localized hydrophobic inner surface near the exit end
providing a polymer capillary tube having an inner diameter between 1 micron to 1000 microns (μm); treating an inner surface of the capillary tube to be hydrophobic between an exit end of the capillary tube to 1 μm to 5000 μm from the exit end.
Localized hydrophobic inner surface near the exit end within a length fraction
providing a polymer capillary tube having an inner diameter between 1 micron to 1000 microns (μm); treating an inner surface of the capillary tube to be hydrophobic between an exit end of the capillary tube to 0.001% to 10% of a length of the capillary tube from the exit end.
Hydrophobic exit end and winding into a coil with specified coil inner diameter
providing a polymer capillary tube having an inner diameter between 1 micron to 1000 microns (μm); treating an inner surface at an exit end of the capillary tube to be hydrophobic, winding the polymer capillary tube into a coil, the coil having an inner diameter between 11 millimeters and 24.5 millimeters (mm).
Across the independent claims, the core claimed coverage centers on manufacturing a tear secretion measurement apparatus using a polymer capillary tube in which the inner surface is made hydrophobic only at an exit-end region, with the hydrophobic region extent defined either by a distance from the exit end or by a fraction of tube length. In one independent claim, the hydrophobic exit end is combined with winding the polymer capillary tube into a coil with a specified coil inner diameter.
Stated Advantages
Reduces eye irritation by applying a soft silicone rubber coating at the entrance end.
Documented Applications
A tear secretion measurement apparatus for measuring lacrimal tear secretion, including functioning as a Schirmer-strip replacement for short-term collection.
Measurement of tear amount by weighing or volume, with optional analysis of tear liquid by liquid chromatography.
Long-term wear use with fluid excess returning to the eye via a bypass channel configured for a predetermined liquid-to-bypass ratio.
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