Tear Evaporation Flux May Affect Contact Lens-Associated Symptomatology

Tear evaporation flux may be higher among contact lens wearers who report experiencing contact lens-associated symptoms compared with those who are asymptomatic during contact lens wear, according to an investigation published in Contact Lens and Anterior Eye. However, the report failed to establish statistical significance between this variable and symptomatology. 

Researchers enrolled contact lens wearers recruited from the University of California, Berkeley Clinical Research Center database in the investigation. Contact lens users who were symptomatic (n=21) and asymptomatic (n=21) underwent lipid-layer thickness, ocular surface temperature decline rate, non-invasive tear break-up time (NITBUT), and tear meniscus height measurements during 5 study visits. An open-chamber evaporimeter that controlled airflow humidity and temperature allowed the team to obtain accurate tear evaporation flux measurements. 

A slower evaporation flux was associated with a thicker lipid layer (P <.001), while higher evaporation flux correlated with faster NITBUT (P =.006) and ocular surface temperature decline rate (P <.001).   

The report revealed a trend toward higher tear evaporation flux among individuals demonstrating contact lens-related symptoms compared with participants who were asymptomatic (P =.053). Since the investigation excluded individuals who discontinued contact lens wear due to symptoms, the researchers speculate that this association could have achieved statistical significance with their inclusion. 

“The statistically significant relationships between lipid-layer thickness and tear-evaporation flux, and between tear-evaporation flux and NITBUT reinforce the importance of the tear lipid layer in regulating tear thickness decline and, therefore, pre-corneal and pre-lens tear osmolarity during no-lens wear and lens wear, respectively,” the study authors explain. “Since pre-corneal tear-film hyperosmolarity has been shown to be related to dry eye, and pre-lens tear film hyperosmolarity has been shown to increase osmolarity in post-lens tears, results from this study provide additional evidence for the importance of the lipid-layer thickness on reducing dryness symptoms for both no-lens and lens wear.”

A small sample size, allowing participants to wear their habitual contact lenses, and potential conditions that increased airflow velocity during tear evaporation flux measurements are acknowledged limitations to the research. 

Disclosure: This research was supported by CooperVision. One study author declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.