Contact lens wearers may be able to decrease their tear osmolarity—and in turn, their risk of dry eye—if they switch to daily disposable lenses and wear them on a strict schedule, a team of researchers from Poland and Spain suggest.

Their study recruited 50 healthy young habitual contact lens wearers (33 female and 17 male) who were approximately 26 years old. Prior to the study, 32 (64%) wore monthly lenses, 15 (30%) were in a two-week modality and three (6%) wore daily disposables that were different than the study lens. The participants wore their lenses at least eight hours a day for at least a year before being enrolled in the investigation.

The researchers refit 34 patients with silicone hydrogel and 16 with hydrogel daily disposable soft lenses. Subjects were instructed to follow strict wearing rules.

The team conducted follow-up visits after three, six and 12 months of contact lens wear, as well as a post-study visit when lenses weren’t worn. The researchers conducted osmolarity testing, and patients recorded their ocular symptoms and lens discomfort on Ocular Surface Disease Index (OSDI) and Contact Lens Dry Eye Questionnaire (CLDEQ).

The study reported a downward trend of tear osmolarity over the course of the study in both eyes. At the end of the investigation, the readings for all subjects were comparable with the values commonly found in healthy non-wearers.

Additionally, they observed a statistically significant decrease in tear osmolarity in only initially symptomatic subjects. They found no major differences in OSDI or CLDEQ scores between baseline and the 12-month visit. This finding was not surprising, since there is generally a lack of correlation between signs and symptoms of dry eye, the researchers said. However, post-study OSDI scores were lower compared with baseline.

Decreases in osmolarity may also be attributed to better compliance, a more moderate wearing schedule, appropriate contact lens fit and the lack of preservatives from lens solutions, the researchers added.

 Also of note: the study found no marked difference in osmolarity levels between the silicone hydrogel and hydrogel groups, which suggests lens material may not be as important in the osmolarity decrease as lens modality and the participants’ compliance.

Garaszczuk IK, Mousavi M, Szczesna-Iskander DH, et al. A 12-month prospective study of tear osmolarity in contact lens wearers refitted with daily disposable soft contact lenses. Optom Vis Sci. 2020;97(3):178-85.