Nancy Keir is Senior Clinical Manager, New Technologies, Research & Development at CooperVision.
It’s well known that contact lens discomfort continues to remain the primary reason for discontinuation of lens wear 1-3 and that approximately 50% of those wearing contact lenses report discomfort at the end of the day.4,5 The mystery of contact lens discomfort is that there are many wearers with contact lens discomfort without noticeable signs and who note relief almost immediately upon lens removal.4 A combination of intellect, detective skills and science and technology will be necessary to solve this complicated problem. Key questions can provide focus and help lead to a better understanding:
Q1: What group are we targeting?
A study conducted by Glasson et al. focused on the problem of contact lens intolerance and looked at the impact of contact lens wear on protein characteristics of the tear film.6 Intolerance was determined by having subjects wear a particular lens for six hours, after which they were asked to describe their symptoms and to select whether they could be tolerant of lens wear for six hours or less, for a full working day (nine hours), for two days of consecutive daily wear or daily wear of longer than two days. Intolerance to lens wear was subsequently defined as the inability to wear lenses regularly during one working day longer than six hours.
After careful testing under controlled conditions, including repeating all clinical and biochemical tests on two or three days for repeatability, results of this study showed that intolerant wearers had more symptoms and significantly reduced tear volume (meniscus height and phenol red thread test) and tear stability (noninvasive tear break up time (p<0.05) than tolerant wearers; however, there was no association with protein characteristics of the tear film.
Taking a different approach, Young et al.7 investigated subjects with increased dryness symptoms with their lenses at the end of the day. Wearers completed a self-administered short questionnaire based on the Contact Lens Dry Eye Questionnaire.8,9 Qualifying criteria included a combined assessment of the frequency and late-day intensity of dryness. In this study of 226 symptomatic lens wearers, a comprehensive dry eye assessment was completed, with various measures of tear stability, tear volume, blink rate, lens fit, lens surface assessment, tear production and ocular health. Results of this study were that 30% had aqueous tear deficiency, 25% had SCL-induced tear instability, 14% had meibomian gland dysfunction, and 8% had “other” diagnoses. Interestingly, 23% had no clinical signs of dry eye.
Q2: What are possible hypotheses for contact lens discomfort?
To explore whether end-of-day contact lens discomfort is due to the time of day, Tilia et al.10 conducted an experiment where 34 subjects completed testing on five different days. One day no lenses were worn, one day silicone hydrogel lenses were worn bilaterally for 12hrs and on three days silicone hydrogels were worn bilaterally either in the morning, afternoon or evening. Each day, ocular comfort was measured at various times points. Results showed no significant difference between any of the three 4-hour lens wear days, despite a drop-off in comfort with 12hrs of wear. The authors concluded that end-of-day contact lens discomfort is more likely due to the length of wear rather than the time of day lenses are worn.
Papas et al.11 conducted a clever experiment to investigate the consequences of interrupting lens wear on contact lens discomfort. In the first study, subjects (n=27) wore hydrogel lenses bilaterally for 10hrs on two separate days, with comfort being reported at insertion and after 5mins, 5hrs and 10hrs of wear. On Day 2 lenses were removed after the 5hr assessment and either reinserted (n=14) or replaced with new lenses (n=12), with a comfort rating being taken 5mins after re-insertion/replacement. A separate, similar study was also completed (n=24) using a silicone hydrogel lens. For both studies, the results were not influenced by replacing or reinserting lenses midway through the wearing period, suggesting that end-of-day contact lens discomfort is not caused by changes occurring to the lenses during the day.
The Tear Film & Ocular Surface Society conducted a workshop on contact lens discomfort in an attempt to determine what it is, why it occurs and how it can be treated.12 An outcome of this workshop was a definition of contact lens discomfort which will be an extremely useful tool to enable more focused research and to potentially allow for comparisons between studies, if this definition is followed and inclusion criteria are similar. There is no one answer to this complicated problem; however, asking the right questions and correctly putting all of the pieces together may help in the battle against contact lens discomfort.
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8. Young G, Chalmers RL, Napier L, Hunt C, Kern J. Characterizing contact lens-related dryness symptoms in a cross-section of UK soft lens wearers. Cont Lens Anterior Eye 2011;34:64–70.
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10. Tilia D, Lazon de la Jara P, Weng RB, Willcox M, Holden B, Papas EB. Is contact lens comfort influenced by time of day? Optom Vis Sci 2010;87:E-abstract 100824.
11. Papas EB, Tilia D, Tomlinson D, Williams J, Chan E, Chan J, Golebiowski B. Consequences of wear interruption for discomfort with contact lenses. Optom Vis Sci 2014;91(1)[epub ahead of press]
12. The TFOS International Workshop on Contact Lens Discomfort. Invest Ophthalmol Vis Sci 2013;54(11): Special Issue.