Tear film measurement by optical reflectometry technique

Area of Science:

• Ophthalmology
• Biomedical Optics
• Surface Science

Background:

• Accurate tear film evaluation is crucial for diagnosing dry eye disease and assessing contact lens comfort.
• Existing methods for tear film analysis can be time-consuming or lack precision.
• A need exists for a rapid, non-invasive technique to quantify tear film dynamics.

Purpose of the Study:

• To develop and validate a novel fiber-based optical reflectometer system for rapid tear film evaluation.
• To assess the system's capability in measuring tear film thickness and thinning rates in artificial and human eyes.
• To determine the accuracy and practical usability of the reflectometer for both pre- and post-contact lens wear.

Main Methods:

• Utilized an optical reflectometer with a galvanometer scanner for beam alignment.
• Employed optical fibers for illumination delivery and reflectance collection across wavelengths.
• Determined film thickness by fitting spectral reflectance data.
• Acquisition time of 15 ms and beam alignment of 1 s were achieved.

Main Results:

• Successfully quantified tear film thickness and thinning rate on a model eye (minimum thickness ~0.3 μm).
• Demonstrated high-contrast signal acquisition from human tear films, measuring thickness from 3.69 to 1.31 μm.
• Observed lipid layer thickness variations between 41 and 67 nm.
• Achieved measurement accuracy better than ±0.58% with minimal refractive index error.

Conclusions:

• The fiber-based reflectometer system provides a compact, user-friendly, and highly accurate method for evaluating tear film dynamics.
• The system's speed and precision enable real-time monitoring of tear film changes in various conditions, including contact lens wear.
• This technology holds potential for improved diagnosis and management of ocular surface diseases.