Key messages
• Lubricating eye drops, including saline, may help to reduce contact lens discomfort in adults. The drops do not appear to cause irritation or harm to the surface of the eye.
• Treating contact lens discomfort with lubricating drops (including saline) is a viable option. However, more studies are needed to measure their effect and to determine which drops work best with different contact lenses and wearing schedules.
What is contact lens discomfort?
Contact lens discomfort means eye irritation that is relieved when the wearer removes their contact lenses. Contact lens wearers may notice dryness, awareness of the lens in their eye, irritation, blurry vision, or a combination of these.
How is contact lens discomfort treated?
The most common way to treat contact lens discomfort is to use over-the-counter lubricating drops or saline drops, but eye care specialists might also change the contact lens brand, the contact lens care system, or the contact lens wearing schedule.
What did we want to find out?
We wanted to know if lubricating drops would reduce the discomfort in contact lens wearers, and whether the drops would have unwanted effects.
What did we do?
We searched for studies that compared lubricating drops against no treatment, lubricating drops against saline, or saline against no treatment in adult contact lens wearers. We compared and summarized the results of the studies and rated our confidence in the evidence based on factors such as study design and methods.
What did we find?
We found seven studies, including 463 adults, conducted in the USA, Canada, Italy, and France. Four studies compared lubricating drops with no treatment, two compared lubricating drops with saline, and one compared saline drops with no treatment.
Lubricating drops, including saline, may help reduce contact lens discomfort compared with no treatment, and lubricating drops compared with saline may not differ in their effect on contact lens discomfort. However, we are very uncertain about these results. Lubricating drops may have no effect on scratched cornea (the clear covering of the eye) and eye redness.
It appears that lubricating drops do not have unwanted effects that would stop contact lens wearers from using them.
What are the limitations of the evidence?
We only included seven studies in the review. Some studies did not use a valid instrument to measure contact lens discomfort. A valid instrument could be a questionnaire that has been tested and proven to reliably measure how a patient feels, such as the 8-item Contact Lens Dry Eye Questionnaire (CLDEQ-8). The studies included small numbers of contact lens wearers who used the drops for a short period of time, and only one study reported participants' race or ethnicity. Therefore, the results may not apply to all adults with contact lens discomfort. In general, this review provided useful information for patients and eye care practitioners, but more research needs to be done to improve our confidence in the results.
How up to date is this evidence?
The evidence is current to May 2024.
Very low-certainty evidence suggests that lubricating drops may improve contact lens discomfort compared with no treatment, but may have little or no effect on contact lens discomfort compared with saline. Low-certainty evidence also suggests that lubricating drops may have no unwanted effects that would lead to discontinuation over one to four weeks.
Current evidence suggests that prescribing lubricating drops (including saline) to people with contact lens discomfort is a viable option. However, most studies did not assess patient-reported contact lens (dis)comfort using a validated instrument. Therefore, further well-designed trials are needed to generate high-certainty evidence on patient-reported outcomes as well as on longer-term safety outcomes.
Contact lens discomfort is a symptom-based clinical diagnosis that affects 13% to 75% of contact lens wearers. The Tear Film and Ocular Surface Society defines contact lens discomfort as "a condition characterized by episodic or persistent adverse ocular sensations related to lens wear either with or without visual disturbance, resulting from reduced compatibility between the lens and ocular environment, which can lead to decreased wearing time and discontinuation from lens wear." Signs of the condition include conjunctival hyperemia, corneal and conjunctival staining, altered blinking patterns, lid wiper epitheliopathy, and meibomian gland dysfunction. Eye care specialists often treat contact lens discomfort with lubricating drops, including saline, although there is no clear evidence showing this treatment is effective and safe.
To evaluate the efficacy and safety of lubricating drops for ocular discomfort associated with contact lens wear in adults.
We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register), MEDLINE, Embase.com, two other databases, and two trials registries to May 2024, without date or language restrictions.
We included parallel-group randomized controlled trials (RCTs) that evaluated lubricating drops, including saline, versus no treatment, or that evaluated lubricating drops versus saline, in adult contact lens wearers. We included studies regardless of publication status, language, or year of publication.
We applied standard Cochrane methodology. The critical outcome was contact lens discomfort. Important outcomes were corneal fluorescein staining and conjunctival redness. Adverse outcomes were incident microbial keratitis, inflammatory corneal infiltrates, and participant discontinuation. We assessed risk of bias for outcomes reported in the summary of findings table using the Cochrane risk of bias tool RoB 2, and we rated the certainty of the evidence using GRADE.
We included seven RCTs conducted in the USA, Canada, Italy, and France. They randomized a total of 463 participants to lubricating drops, saline, or no treatment. Four trials evaluated lubricating drops and saline versus no treatment, but one of them provided no usable outcome data. Three trials evaluated lubricating drops versus saline.
Study characteristics
All trial participants were adults, and the mean age ranged from 25.7 years to 36.7 years. The proportion of women varied from 15% to 82%. The trials lasted between one and four weeks. Of the five trials that reported contact lens discomfort, we judged three at high risk of bias, and considered the other two had some risk of bias concerns.
Lubricating drops (including saline) versus no treatment
Lubricating drops compared with no treatment may reduce contact lens discomfort, measured on a 37-point scale (lower is better), but the evidence is very uncertain (mean difference [MD] −5.9 points, 95% confidence interval [CI] −3.74 to −8.05; 2 RCTs; 119 participants). One trial found no difference between lubricating drops and no treatment in "end-of-day" comfort. The trial that compared saline with no treatment provided no results for the control group.
Two studies measured corneal fluorescein staining on a scale of 0 to 20 (lower is better). We found low-certainty evidence of little to no difference between lubricating drops and no treatment in changes in the extent (MD −0.15 points, 95% CI −0.86 to 0.56; 2 RCTs; 119 participants), depth (MD −0.01 points, 95% CI −0.44 to 0.42; 2 RCTs; 119 participants), or type (MD 0.04 points, 95% CI −0.38 to 0.46; 2 RCTs; 119 participants) of corneal fluorescein staining scores. Regarding conjunctival redness, measured on a scale of 0 to 4 (lower is better), there was low-certainty evidence of little to no difference between lubricating drops and no treatment in nasal region scores (MD 0.10, 95% CI −0.29 to 0.49; 1 RCT; 73 participants) and temporal region scores (MD 0.00, 95% CI −0.39 to 0.39; 1 RCT; 73 participants).
No studies reported microbial keratitis or inflammatory corneal infiltrates, and no trials reported vision-threatening adverse events up to four weeks of treatment. All trials reported the proportion of participants who discontinued participation. In two trials, no participants left any treatment group. Our meta-analysis of another two studies suggests little difference in the number of people who dropped out of the lubricating treatment group versus the no treatment group (risk ratio [RR] 1.42, 95% CI 0.19 to 10.94; 138 participants; low-certainty evidence).
Lubricating drops versus saline
Lubricating drops may have little to no effect compared with saline on contact lens discomfort measured on a visual analog scale of 0 to 100 (lower is better), but the evidence is very uncertain (MD 9.5 points, 95% CI −4.65 to 23.65; 1 RCT; 39 participants). No studies reported corneal fluorescein staining or conjunctival redness.
No studies reported microbial keratitis or inflammatory corneal infiltrates, and no trials reported vision-threatening adverse events up to four weeks of treatment. Our meta-analysis of three studies suggests little difference in the number of people who dropped out of the lubricating treatment group versus the saline group (RR 1.56, 95% CI 0.47 to 5.12; 269 participants; low-certainty evidence).