Tear-film evaporation flux and its relationship to tear properties in symptomatic and asymptomatic soft-contact-lens wearers

Young Hyun Kim; Andrew D Graham; Wing Li; Thomas J Dursch; Cheng-Chun Peng; Clayton J Radke; Meng C Lin

doi:10.1016/j.clae.2023.101850

Tear-film evaporation flux and its relationship to tear properties in symptomatic and asymptomatic soft-contact-lens wearers

Cont Lens Anterior Eye. 2023 Aug;46(4):101850. doi: 10.1016/j.clae.2023.101850. Epub 2023 May 1.

Authors

Young Hyun Kim¹, Andrew D Graham², Wing Li³, Thomas J Dursch⁴, Cheng-Chun Peng⁵, Clayton J Radke⁶, Meng C Lin⁷

Affiliations

¹ Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States; Clinical Research Center, Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States; Chemical and Biomolecular Engineering Department, University of California, Berkeley, CA 94720, United States.
² Clinical Research Center, Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States.
³ Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States; Clinical Research Center, Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States.
⁴ Clinical Research Center, Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States; Chemical and Biomolecular Engineering Department, University of California, Berkeley, CA 94720, United States.
⁵ Clinical Research Center, Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States; Chemical and Biomolecular Engineering Department, University of California, Berkeley, CA 94720, United States; CooperVision Inc., Pleasanton, CA 94588, United States.
⁶ Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States; Chemical and Biomolecular Engineering Department, University of California, Berkeley, CA 94720, United States.
⁷ Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States; Clinical Research Center, Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, CA 94720, United States. Electronic address: mlin@berkeley.edu.

PMID: 37137757
DOI: 10.1016/j.clae.2023.101850

Abstract

Purpose: With soft-contact-lens wear, evaporation of the pre-lens tear film affects the osmolarity of the post-lens tear film and this can introduce a hyperosmotic environment at the corneal epithelium, leading to discomfort. The purposes of the study are to ascertain whether there are differences in evaporation flux (i.e., the evaporation rate per unit area) between symptomatic and asymptomatic soft-contact-lens wearers, to assess the repeatability of a flow evaporimeter, and to assess the relationship between evaporation fluxes, tear properties, and environmental conditions.

Methods: Closed-chamber evaporimeters commonly used in ocular-surface research do not control relative humidity and airflow, and, therefore, misestimate the actual tear-evaporation flux. A recently developed flow evaporimeter overcomes these limitations and was used to measure accurate in-vivo tear-evaporation fluxes with and without soft-contact-lens wear for symptomatic and asymptomatic habitual contact-lens wearers. Concomitantly, lipid-layer thickness, ocular-surface-temperature decline rate (i.e., °C/s), non-invasive tear break-up time, tear-meniscus height, Schirmer tear test, and environmental conditions were measured in a 5 visit study.

Results: Twenty-one symptomatic and 21 asymptomatic soft-contact-lens wearers completed the study. A thicker lipid layer was associated with slower evaporation flux (p < 0.001); higher evaporation flux was associated with faster tear breakup irrespective of lens wear (p = 0.006). Higher evaporation flux was also associated with faster ocular-surface-temperature decline rate (p < 0.001). Symptomatic lens wearers exhibited higher evaporation flux than did asymptomatic lens wearers, however, the results did not reach statistical significance (p = 0.053). Evaporation flux with lens wear was higher than without lens wear but was also not statistically significant (p = 0.110).

Conclusions: The repeatability of the Berkeley flow evaporimeter, associations between tear characteristics and evaporation flux, sample-size estimates, and near statistical significance in tear-evaporation flux between symptomatic and asymptomatic lens wearers all suggest that with sufficient sample sizes, the flow evaporimeter is a viable research tool to understand soft-contact-lens wear comfort.

Keywords: Contact-lens-wear discomfort; Evaporative dry eyes; Flow evaporimeter; Hyperosmolarity; Soft contact lens; Tear evaporation; Tear film; Tear lipid layer.

MeSH terms

Contact Lenses, Hydrophilic*
Epithelium, Corneal*
Humans
Lens, Crystalline*
Lipids
Tears

Substances

Lipids