# Correlating the microstructural thickness variations of the tear film lipid layer with clinical characteristics of dry eye with a novel optical method

> **NIH NIH R01** · UNIVERSITY OF SOUTH FLORIDA · 2024 · $380,639

## Abstract

Project Summary
 In the anterior eye, the precorneal tear film (PCTF) acts as the interface between the ocular surface and
external environment and plays a critical role in maintaining ocular surface homeostasis. In dry eye disease
(DED), the PCTF becomes thinner, and destabilizes (evaporates) rapidly leading to hyperosmolarity,
inflammation, and ocular surface desiccation. In 2020, the National Eye Institute (NEI) released a Notice of
Special Interest (NOSI) for the Anterior Segment Initiative (ASI), “Identification and Development of New
Biomarkers and Effective Methods to Diagnose Dry Eye Disease.” The notice highlighted a critical need for
biomarkers and methods to diagnose DED prior to the onset of symptoms. The overall goal of this proposal is to
characterize microstructural thickness variations of the tear film lipid layer (TFLL) and their association with
clinical characteristics of DED. TFLL, the outmost layer of PCTF, overlies the aqueous phase, and serves as the
barrier against evaporative aqueous loss, and stabilize it by facilitating the spread of its aqueous compartment
and reducing surface tension. However, the exact mechanism by which the TFLL retards tear evaporation and
promotes PCTF stability remains poorly understood. For instance, while most would agree that a uniform and
thicker TFLL would be more protective against evaporation, and therefore prevent DED, this relationship remains
controversial in the literature; resolution of this controversy forms the basis of this proposal. Under a NIH/NEI
grant in 2021(R21EY033029), we constructed a novel laser source point-scanning interferometer that enables
the in vivo assessment of dynamics of PCTF and related structures of TFLL with unprecedented resolution and
sensitivity. Using this powerful system, we propose to address critical yet previously unexplored and often
inconsistent associations between TFLL and examination findings of PCTF. The central hypothesis of the
proposed research is that thickness variations in the microstructure of TFLL are associated with clinical
characteristics of DED. We will test this hypothesis in concurrent Specific Aims: Aim 1: Verify and quantify the
inversely relationship between TFLL thickness and PCTF evaporation rate. We hypothesize that TFLL thickness
is inversely proportional to PCTF evaporation, with “thin” regions of the TFLL allowing excessive loss of aqueous
tears. Aim 2: Quantify the impact of TFLL thickness variations on PCTF instability. We hypothesize that steep
stress gradients at the interface between “thin” and “thick” regions of the TFLL cause PCTF instability.
 Collectively, the proposed studies will introduce two new parameters to characterize the lipid layer
microstructure and correlate them with PCTF evaporation and instability, which will be tested and validated with
our novel high-resolution interferometric system. With further clinical validation, these parameters will allow for
early, non-invasive assessment of DED and infor...

## Key facts

- **NIH application ID:** 10833127
- **Project number:** 5R01EY034990-03
- **Recipient organization:** UNIVERSITY OF SOUTH FLORIDA
- **Principal Investigator:** Yuqiang Bai
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $380,639
- **Award type:** 5
- **Project period:** 2023-05-01 → 2028-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10833127

## Citation

> US National Institutes of Health, RePORTER application 10833127, Correlating the microstructural thickness variations of the tear film lipid layer with clinical characteristics of dry eye with a novel optical method (5R01EY034990-03). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10833127. Licensed CC0.

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