Does placebo effect exist in contact lens discomfort management?

Abstract

Purpose

To study the effect of daily disposable contact lens (DDCL) refitting in monthly contact lens (CL) wearers suffering from contact lens discomfort (CLD), and to assess if there is a placebo effect associated with this CLD intervention.

Methods

Symptomatic CL wearers, according to the Contact Lens Dry Eye Questionnaire 8 (CLDEQ-8 ≥ 12 points), were divided into two groups. The study group was provided with DDCLs (delefilcon A) and the control group with a masked pair of their habitual monthly CLs (placebo effect) and were assessed after one month. Then, the control group was provided with the same DDCLs and evaluated one month later. The symptoms were recorded with the CLDEQ-8 and global rating of change scale (GRCS). Non-invasive tear break-up time (NITBUT), conjunctival hyperaemia, fluorescein staining, and lid wiper epitheliopathy (LWE) were evaluated. Changes between visits, groups, and the effect of each intervention were analysed.

Results

Thirty-one participants (mean age: 23.2 ± 5.3 years) were recruited. The study group (n = 14) showed an improvement of -39.6 ± 25.8 % (p < 0.001) in CLDEQ-8 and 31.3 ± 14.6 points in GRCS (p < 0.001) after one month of DDCL use, while no changes in clinical tests were found. In the control group (n = 17), symptoms improved significantly after wearing the masked monthly CL (CLDEQ-8: -26.1 ± 31.0 %, p = 0.03; GRCS: 14.9 ± 17.0, p = 0.002), however a worsening in bulbar (26.5 ± 40.0 %; p = 0.02) and limbal hyperaemia (21.6 ± 34.7 %, p = 0.02) and an improvement of -19.1 ± 37.0 % (p = 0.049) in LWE was found. When the control group was fitted with the DDCL, improvements in GRCS (20.5 ± 25.5, p = 0.02), NITBUT (37.9 ± 42.3 %, p = 0.002), and conjunctival staining (-47.1 ± 59.9 %, p = 0.005) were noted.

Conclusions

Refitting symptomatic monthly CL wearers with Delefilcon A DDCL is effective in reducing symptoms related to CLD. However, clinicians and researchers must be aware of the existence of a placebo effect when assessing the effectiveness of any CL refitting.

Introduction

Contact lens discomfort (CLD) is a condition that affects up to 50 % of contact lens (CL) wearers, and eventually leads to CL drop out [1]. Discomfort is considered to be ‘a mental or bodily distress, or something that disturbs one’s comfort’ [2]. Regarding lens wear, a comfortable lens wear is the ability to wear the lens without the sensation of wearing it [3]. The Tear Film and Ocular Surface (TFOS) International Workshop on CLD resulted in the following definition of CLD: ‘a condition characterised by episodic or persistent adverse ocular sensations related to lens wear, either with or without visual disturbance, resulting from reduced compatibility between the CL and the ocular environment, which can lead to decreased wearing time and discontinuation from CL wear’ [3]. CLD is primarily diagnosed according to symptomatology as opposed to the observation of signs; thus, the use of questionnaires is recommended [4]. Therefore, CLD should be evaluated using instruments or questionnaires that measure parameters of discomfort unique to this condition [5].

CL comfort is a result of multiple factors related to inherent or modifiable patient factors, ocular or external environmental factors, or the CL itself [3]. Furthermore, wettability of a CL on the eye is considered a major contributing factor of CLD [6]. Wettability is described as the ability of the tear film to spread and remain on the surface of a CL [7]. It is well known that all soft CLs show a gradual worsening in wettability over time [8], with a decrease in the comfortable wearing time over the day as well as over the life of the lens [9,10]. Some studies related these changes to the presence of deposits on the CL surface, which tends to exacerbate the effects of poor pre-lens wetting [11] and alter lens parameters and compliance [[12], [13], [14]]. Therefore, increasing the replacement frequency of the CL seems like a good approach to avoid or at least reduce CLD. In addition, as care systems may contribute to CLD [15], changing the CL replacement to a daily disposable CL (DDCL) could be one of the best solutions to reduce symptoms or complications of CLD [15]. A survey performed in 2018 showed that 52 % of the practitioners would refit their CLD patients with a different CL with a more frequent replacement schedule being the first-line recommendation for alleviating CLD [16].

Multiple, often co-existing, causes contribute to CLD, making it difficult to isolate the causative factor. Thus, when a new CL is fitted, it is difficult to identify the reason for comfort as a single parameter or characteristic of the CL [15]. Moreover, when a clinician provides instructions to manage CLD, the CL wearer can develop a desire to respond to the therapy, even though the CLD intervention itself might not provide any real benefit. This can be considered a placebo effect, which has been studied in dry eye disease clinical trials [17,18]. The placebo effect may be defined as an effect produced by the symbolic dimensions of treatment, beginning with a positive belief that the treatment or procedure will work and an experience of expectancy that the stimulates specific neurochemical processes [19].

This study aimed to examine the effects of refitting monthly CL wearers who suffer from CLD with DDCLs, and to assess if a placebo effect could affect the subjective outcomes when new CLs are fitted.