The first daily disposable (DD) contact lenses (CLs) came to market in the United States in 1995. Since then, worldwide, the DD modality continues to grow at remarkable rates. Advantages of DD CL wear include the convenience of not needing to utilize cleaning and disinfecting solutions, the freshness of a new contact lens placed on the eyes each day, comfort based on avoidance of lens deposit-induced discomfort that occurs with reusable lenses, and the potential for improved lens-wearing safety with the use of fresh lenses daily. The question is whether these advantages are supported by the evidence obtained from research. We will explore a number of topics related to daily disposable contact lenses and see what current research tells us.

Demographics

According to the annual International Contact Lens Prescribing report for 2020 (Morgan et al, 2021), approximately 38% of CLs prescribed worldwide are DD lenses. Of that total, 14% are hydrogel DDs, and 24% are silicone hydrogel (SiHy) DDs. However, the range varies dramatically from country to country. The highest reported DD fittings come from the United Kingdom, in which 61% of patients are fit into DDs (17% hydrogel, 44% SiHy); the lowest reported numbers come from Colombia, in which only 3% of patients are fit in DDs. For the United States, the report suggests that 34% of patients are fit in DDs (6% hydrogel, 28% SiHy). As more options in DD lens designs come to market, we are seeing continued growth in this segment. Today, DDs are available in sphere, toric, multifocal, color tints, and most recently in myopia management designs.

Comfort

Intuitively, replacing CLs on a daily basis would seem to result in improved long-term comfort. In a study of 83 symptomatic reusable CL wearers who were refit into DDs, Fahmy et al (2010) reported statistically significant improvements in symptom frequency for tired eyes (P < 0.001), irritated eyes (P < 0.001), blurred vision (P < 0.001), redness (P < 0.001), discomfort (P = 0.024), deposits/lens needs cleaning (P < 0.001), and dryness (P < 0.001). Statistically significant improvements in symptom severity were reported for tired eyes (P < 0.001), irritated eyes (P < 0.001), blurred vision (P < 0.001), redness (P < 0.001), discomfort (P = 0.037), deposits/lens needs cleaning (P < 0.001), and dryness (P < 0.001). They concluded that a range of common symptoms can be reduced with a DD lens.

Conversely, Sapkota and co-workers (2018) conducted a longitudinal clinical trial of 47 neophyte myopic subjects fit with a monthly disposable lens (lotrafilcon B, comfilcon A, or balafilcon A) in one eye and a DD lens (nelfilcon A, stenofilcon A, or nesofilcon A) in the other eye, randomly selected. They determined that there was no significant association between the wearing modality and the average comfort level and the reduction of end-of-day comfort (p > 0.05). The issue of CL wearing comfort is likely a multifactorial issue of which replacement frequency is only one element.

Compliance to Replacement

One of the major advantages of daily disposability is that CLs are not given the chance to significantly form deposits prior to replacement. This has an impact on comfort, vision, and potentially on the physiological response. When considering this, practitioners must keep patient behaviors in mind in terms of compliance to prescribed replacement schedules. Dumbleton et al (2013) conducted a survey study of patients wearing DD, monthly, and two-week replacement lenses. They discovered that wearers of two-week lenses were significantly less compliant with replacement compared to wearers of both DDs and one-month replacement lenses, with DD compliance being highest (34% versus 74% and 67%, both p < 0.001).

They also determined that patients who were not compliant with the prescribed replacement frequency had longer intervals between eye examinations and were less likely to purchase an annual supply of lenses.

Rueff et al (2019) confirmed these results. These researchers reported that replacement compliance was once again best with DDs, followed by monthly lenses; the least compliant with replacement were two-week lens wearers. Compliance issues do not relate only to patients, they can also relate to eyecare practitioner (ECP) prescribing habits.

A study of such behavior reported that ECPs most frequently prescribed replacement frequencies that differ from manufacturers’ suggested replacement for two-week lenses. Interestingly enough, this study determined that the greatest compliance by ECPs to manufacturers’ suggested replacement was for monthly lenses over DDs (Dumbleton et al, 2010). Additionally, this study concurred with others in that patient compliance to lens replacement was best with DDs, significantly more so than with monthly lenses; it was worst yet with two-week CLs.

Safety Issues

One of the most compelling attributes of DD CLs is their potential to be a safer alternative in comparison to reusable CLs. The wearing of a fresh lens each day would reduce the bioburden and the potential for numerous complications.

Chalmers and associates (2015) studied the rates of adverse events with hydrogel and SiHy DD CLs in a large post-market surveillance registry. The annualized incidence of symptomatic DD-related adverse events (AEs), including corneal infiltrative events (CIEs), was calculated based on 3,064 surveys from 1,171 subjects during one year. Three independent experts adjudicated potential AE cases. They reported that per-year CIE rates of 0.4% (SiHy DD) and 0% (hydrogel DD) are significantly lower compared to rates reported with reusable SCLs (3% to 4% per year); this indicates improved safety outcomes with these DD lenses.

Stapleton (2020) indicated that rates of microbial keratitis (MK) are lower in DD versus reusable CLs and that in cases of suspected MK with DD wear there are a greater proportion of culture-negative results from corneal scrapings. She felt that this may relate to the absence of a storage case, which may act as a vector for organisms. As it relates to the ocular health and safety of children fit with hydrogel DD CLs, Woods et al (2021) followed 144 children aged 8 to 12 years for six years in a double-masked clinical trial investigating the performance of a dual-focus DD hydrogel CL designed to control myopia progression along with a single-vision hydrogel DD. They noted that no CL-related AEs were classified as serious and that the incidence rate of infiltrative AEs was 0.61% (6.1 per 1,000 wearing-years). The researchers concluded that across the six years, there were no CL-related serious AEs and that biomicroscopy showed no significant changes. Results suggest that children this age can successfully wear DD hydrogel CLs with minimal impact on ocular physiology.

The Need for High Dk

There has been an ongoing controversy regarding the need for high-Dk SiHy materials for DD CLs. Once again, there should be no difference in the need for high-Dk materials according to lens replacement frequency. Diec et al (2018) looked at the subjective, objective, and safety performance of SiHy and hydrogel DD CLs. A retrospective analysis was conducted on 40 participants each in five trials. Lenses were grouped into SiHy and hydrogel designs. Participants attended follow-up visits at baseline, two weeks, and at one and three months. Subjective ratings, AEs, physiological variables, and wearing time were collected at each visit and compared between groups. There was greater increase in limbal redness from baseline in the hydrogel group (P < 0.001), whereas conjunctival staining and indentation were less in the hydrogel group (P < 0.001). No differences in comfortable wearing time were reported between groups (P = 0.41), and comfort at application, during the day, and at end of day was also no different (P ≥ 0.71). Incidence of CIEs (SiHy versus hydrogel: 6.7% versus 2.5%; P = 0.32) and mechanical adverse events (SiHy versus hydrogel: 0.0% versus 0.0%; P = 1.00) were no different. The researchers concluded that though some statistical significance was found between the groups, these differences were within measurement error. Neither material types showed superiority in comfort, and AE rates were low with both material types. These findings suggest that choice of material is a patient and practitioner preference; however, for patients at risk of hypoxia-related complications, SiHy materials should be considered.

Concluding Remarks

DD CLs are progressing to become the dominant modality worldwide. Their advantages resonate with both ECPs and patients. This article looked at a number of issues pertaining to DD CL wear and elucidated what current research is telling us about these issues. Ultimately, the decision of modality will be made cooperatively between ECP and patient. Hopefully, evidence-based information will contribute significantly in this decision. CLS

For references, please visit www.clspectrum.com/references and click on document #306.