Efficacy of over the counter (OTC) artificial tears for dry eye syndrome

Research question

What is the effect of over the counter (OTC) artificial tears on dry eye syndrome?

Background
Dry eye syndrome is a long-term condition that is known to cause eye discomfort and visual disturbances like blurred vision. This condition affects millions of people around the world, and the first-line treatment for dry eye is typically over the counter (OTC) artificial tears. OTC artificial tears are meant to replace or supplement the tears (fluid) that naturally cover the eye’s front surface (cornea and conjunctiva). There are a great number of commercially available artificial tears, yet there is currently no agreement about whether one formulation works better than another at treating dry eye. Our review attempts to bridge this knowledge gap.

Study characteristics
This review included 43 randomized controlled trials (3497 people with dry eye) that compared OTC artificial tears with other OTC artificial tears, with no treatment, or with placebo. We considered participant symptoms to be the primary outcome for this review. We recorded other commonly performed dry eye tests as secondary outcomes (e.g. vision, tear stability). We measured primary and secondary outcomes at two and four weeks, although we also considered other time points in this review. We searched for trials up to December 2015.

Key results
This review analyzed many OTC artificial tear formulations, and most of the literature indicates uncertainty as to which OTC artificial tear works best. The literature also shows that OTC artificial tears may be effective at treating dry eye symptoms and that OTC artificial tears are generally safe, although not without side effects.

We also identified an additional 18 potentially eligible trials that were registered, but did not provide any results or publications. These trials may have enrolled 2079 total participants for whom no data are available. Without the results of these trials, the effects of the OTC artificial tears that they evaluated are unknown.

Quality of the evidence

The overall quality of the evidence was low for the various OTC artificial tear formulations compared in this review. This finding indicates that future published research may have an important impact on the conclusions currently provided in this review.

Authors' conclusions: 

OTC artificial tears may be safe and effective means for treating dry eye syndrome; the literature indicates that the majority of OTC artificial tears may have similar efficacies. This conclusion could be greatly skewed by the inconsistencies in study designs and inconsistencies in reporting trial results. Additional research is therefore needed before we can draw robust conclusions about the effectiveness of individual OTC artificial tear formulations.

Read the full abstract...
Background: 

Over the counter (OTC) artificial tears historically have been the first line of treatment for dry eye syndrome and dry eye-related conditions like contact lens discomfort, yet currently we know little regarding the overall efficacy of individual, commercially available artificial tears. This review provides a much needed meta-analytical look at all randomized and quasi-randomized clinical trials that have analyzed head-to-head comparisons of OTC artificial tears.

Objectives: 

To evaluate the effectiveness and toxicity of OTC artificial tear applications in the treatment of dry eye syndrome compared with another class of OTC artificial tears, no treatment, or placebo.

Search strategy: 

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2015, Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to December 2015), EMBASE (January 1980 to December 2015), Latin American and Caribbean Health Sciences (LILACS) (January 1982 to December 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en) and the US Food and Drugs Administration (FDA) website (www.fda.gov). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 4 December 2015. We searched reference lists of included trials for any additional trials not identified by the electronic searches.

Selection criteria: 

This review includes randomized controlled trials with adult participants who were diagnosed with dry eye, regardless of race and gender. We included trials in which the age of participants was not reported, and clinical trials comparing OTC artificial tears with another class of OTC artificial tears, placebo, or no treatment. This review did not consider head-to-head comparisons of artificial tears with another type of dry-eye therapy.

Data collection and analysis: 

We followed the standard methodological procedures expected by Cochrane. Two authors independently screened the search results, reviewed full-text copies for eligibility, examined risk of bias, and extracted data. We performed meta-analysis for trials that compared similar interventions and reported comparable outcomes with sufficient data. We summarized all other included trial results in the text.

Main results: 

We included 43 randomized controlled trials (3497 participants with dry eye). Due to the heterogeneity of study characteristics among the included trials with respect to types of diagnostic criteria, interventions, comparisons, and measurements taken, our ability to perform meta-analyses was limited. The review found that, in general, there was uncertainty whether different OTC artificial tears provide similar relief of signs and symptoms when compared with each other or placebo. Nevertheless, we found that 0.2% polyacrylic acid-based artificial tears were consistently more effective at treating dry eye symptoms than 1.4% polyvinyl alcohol-based artificial tears in two trials assessing this comparison (175 participants). All other included artificial tears produced contradictory between-group results or found no between-group differences. Our review also found that OTC artificial tears may be generally safe, but not without adverse events. Overall, we assessed the quality of evidence as low due to high risks of bias among included trials and poor reporting of outcome measures which were insufficient for quantitative analysis. Furthermore, we identified an additional 18 potentially eligible trials that were reported only in clinical trial registers with no associated results or publications. These trials reportedly enrolled 2079 total participants for whom no data are available. Such lack of reporting of trial results represents a high risk of publication bias.

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