In recent years, contact lenses (CLs), especially soft CLs (SCLs) made of silicone hydrogel material (SiHy-SCLs), have been constantly evolving with new technologies [1–2]. Additionally, new materials and surface surfactants have been added to the design of SiHy-SCLs [3, 4], which have led to an increased biocompatibility of the SCL surface with the human cornea and reduced irritation to the human cornea and conjunctiva [5, 6].
Several studies have reported on the relationship between SCL wear and eye dryness and discomfort [7, 8, 9, 10]. A large population-based study conducted in Canada during the mid-1990s investigated the relationship between CL and dry eye and reported that approximately 50.1% of 3,285 CL wearers experienced dry eye symptoms compared to 21.7% of 10,232 non-CL wearers [11]. In a recent Japanese study, among 105 CL wearers, the prevalence of severe dryness symptoms was 28% in men and 35% in women [12]. The prevalence of dry eye disease among 1,298 CL-wearing high school students was reported to be 37% [13]. A recent study conducted in Shandong, China, reported a 32.8% prevalence of dryness symptoms in 122 high school CL wearers [14].
Dry eyes and ocular discomfort are the main reasons for discontinuing SCL wear [15]. Previous reports observed a dropout rate of approximately 40% among CL wearers abandoning their CLs within 4 months [7]. In addition, a literature review of studies conducted over the past 20 years reported that 23–94% of CL wearers experienced discomfort [8]. Furthermore, studies have reported that approximately 12–51% of CL wearers discontinue using CLs [7, 16, 17, 18, 19]. These studies highlight the importance of selecting comfortable SCLs that are less likely to cause dry eye symptoms in first-time SCL wearers to avoid discontinuation of SCL wear.
In Japan, a new SiHy-SCL (Precision 1®, Alcon Japan, Inc., Tokyo, Japan) made of verofilcon A material was introduced in March 2021. Verofilcon A was first introduced in Oceania and the United States, and comfort studies on this material have been conducted in Australia/New Zealand and the United States [20, 21]. A survey conducted in Australia and New Zealand involving 129 new SCL wearers aged 18 years and older revealed that 91% agreed that "verofilcon A is the preferred lens," 79% agreed that "verofilcon A gives me the option of not wearing glasses," and 70% agreed that " verofilcon A is the best lens to start the contact lens wearing experience" [20]. In the United States, a randomized crossover clinical trial was conducted with two different SCLs, verofilcon A and etafilcon A, in 96 participants who were already wearing CL [21]. The results demonstrated that 73.9% of the participants preferred verofilcon A to etafilcon A. Additionally, satisfaction with visual acuity, SCL handling, and wearing comfort was significantly better for verofilcon A than that for etafilcon A [21]. These results suggest that verofilcon A provides a positive wearing experience among SCL users.
Decreased ocular surface moisture is the most important factor preventing continued SCL wear. The SCL placed on the corneal surface divides the tear film into two interfaces: the pre-SCL and post-SCL tear films [22, 23]. Of these, the amount of lipid layer and aqueous phase in the former pre-SCL tear film depends on the contact lens material and design [22, 24]. To date, various non-invasive methods have been employed for measuring tear film break-up time (BUT) on the SCL surface to assess non-invasive BUT (NIBUT), including (1) direct observation of SCL surface [25], (2) observation of the pre-SCL tear film [26], (3) assessment of color patterns using lipid layer interferometry [27, 28], (4) measurement of tear fluid meniscus height [29], and (5) the use of tear interferometer DR-1α® [30]. Among these, the DR1-α is well-established as an instrument that can measure NIBUT objectively and reproducibly. Therefore, in this study, the DR-1α® was used to measure the tear fluid breakup time on the CL surface.
Verofilcon A was developed as an SCL with a SiHy-SCL water gradient. The lens surface consists of a SiHy core containing 33% water, while the outer surface forms a layer containing 80% water [31]. The SCL has a lubricated surface with continuous high oxygen transmission [31]. This study aimed to measure NIBUT on the verofilcon A material SCL surface in the first-time SCL wearers and examine the relationship between NIBUT and comfort experienced with verofilcon A SCL wear.