Although soft contact lenses (SCLs) have changed significantly over the past 10 years with the introduction of silicone hydrogel materials and newer designs, discontinuation of wear remains an important factor that limits the number of successful wearers.1,2 Ocular surface symptoms such as discomfort and dryness are most often reported as the chief cause of discontinuation for both hydrogel and silicone hydrogel lenses.2–4 In a cross-sectional survey of patients presenting for eyecare,4 >40% of former SCL wearers cited dryness as their primary reason to discontinue use of lenses, and this ranking has been confirmed in other recent studies.2
Dryness and discomfort with SCL use are very common. The prevalence of discomfort and dryness symptoms among SCL wearers is high, approximately 50%, which is at least double than that reported by subjects of similar age who were not using contact lenses.4,5 Even though so many SCL wearers report dryness and discomfort, there is no established level of symptoms that is considered clinically significant. Definitive diagnosis of SCL-related dryness remains a significant challenge, in part, because it is not a disease, per se, but is a symptomatic condition that is amenable to changes in SCL material6–8 or lens care products9,10 that can ameliorate symptoms. Finally, the SCL wearer may choose to cease lens wear altogether as a remedy for dryness symptoms.4
Recently the report from the 2007 Dry Eye Workshop included contact lens-related dry eye in the evaporative category.11 Soft contact lens wear is associated with reversible changes in corneal and conjunctival sensitivity and inflammation that may impact dryness symptoms.12–15 The potential to reverse SCL-related dryness creates a considerable need for a well-designed validated questionnaire for SCL-related dryness that is capable not only of assisting in diagnosis but also in measuring change in the condition that can be improved by available treatments. A number of questionnaires exist, but have not been validated so that the user knows the clinical meaning of scores or change in scores. A valid questionnaire should be able to identify SCL wearers who are struggling with clinically significant SCL-related dry eye complaints16 and be sensitive enough to track their progress when treated with products designed to reduce those symptoms.17,18
The Contact Lens Dry Eye Questionnaire (CLDEQ) was developed more than a decade ago to measure dryness symptoms among contact lens wearers.19,20 The CLDEQ instrument was originally designed in parallel to the Dry Eye Questionnaire (DEQ) for use in patients who do not wear contact lenses. The long forms of both the CLDEQ and DEQ instruments query contact lens-wearing history, frequency and diurnal intensity, and intrusiveness of nine ocular surface symptoms, along with questions about treatments, computer use, and environmental triggers. Recently, a validated five-item short form of the Dry Eye Questionnaire, the DEQ-5, was developed for patients who do not wear contact lenses.21 The DEQ-5 instrument uses a scoring system that is anchored by the patient's self-assessment of dry eye severity and contains five items. The purpose of this study was to develop and validate a short version of the CLDEQ for SCL wearers by identifying a set of questions that reflected satisfaction and overall opinion of SCLs that was also responsive to change among wearers of modern SCL materials.
The development of the short form of the CLDEQ was conducted in two phases. Both phases of this clinical research were conducted after institutional review board approval. All subjects signed informed consent before enrollment, and the studies were conducted in compliance with the Declaration of Helsinki and local Health Insurance Portability and Accountability Act guidelines.
This study took place in two phases, an item reduction phase and a known groups validity phase. Table 1 shows the lenses used in each phase of the research, although results were analyzed and displayed regardless of lens type. Subjects in both phases were included if they were at least 18 years old, if they needed bilateral correction, were in good general health, were willing and able to follow instructions, and were a current full-time and adapted wearer of SCLs. Subjects were not enrolled into the study if they were using monovision correction, were wearing rigid gas-permeable lenses, had clinically significant (grade 3 or 4) anterior segment abnormalities (or any iritis or any infection of the eye, lids, or adnexa), had ocular or systemic disease that would preclude SCL wear, or best-corrected Snellen visual acuity of <20/30 in either eye, or were pregnant or lactating females.
Item Reduction Phase
The purpose of the item reduction phase was to determine which symptoms and SCL-wearer coping mechanisms most highly correlated with the subjects' overall opinion of the SCLs at all study visits. This step was completed with data from a small study sample at the Indiana University School of Optometry. After signing consent documents, 38 (n = 38) frequent replacement SCL wearers completed a prospective randomized, cross-over SCL clinical trial that lasted for 4 weeks. Subjects were randomized at baseline to daily wear of either senofilcon A (Johnson & Johnson Vision Care, Inc, Jacksonville, FL) or balafilcon A (Bausch & Lomb, Rochester, NY) and then crossed over to the other lens at the 2-week visit (Table 1). All subjects were given OPTI-FREE EXPRESS MPDS (Alcon Laboratories, Ft. Worth, TX) with a screw-top lens case, and OPTI-FREE EXPRESS Rewetting Drops (Alcon Laboratories, Ft. Worth, TX) as needed.
At each visit (baseline, 1, and 2 weeks after each cross over for a total of five visits), responses to the long form of the CLDEQ were analyzed to identify items with the highest correlation to overall opinion of the SCLs at that visit (Poor, Fair, Good, Very Good, and Excellent). Groups of items that were most often highly correlated with overall opinion were tested in versions of the short form of the CLDEQ instrument after checking for redundant information (high inter-item correlation). Items with low correlations were not included in the combinations of questions that were tested. Items were removed in order of lower to higher correlation until there was no further impact on the analysis of variance (ANOVA) for the overall relationship to overall opinion of SCLs.
Known Groups Validity Phase
The purpose of the known groups validity phase was to validate the short CLDEQ-8—consisting of eight questions—by testing the sum scores for their ability to reflect overall opinion of habitual SCLs at baseline and for the score's responsiveness to change in overall opinion after randomization to two silicone hydrogel SCL materials. To accomplish this, the short form of the CLDEQ-8 was fielded to a much larger convenience sample in 24 North American clinical sites as part of a larger randomized prospective clinical trial. Subjects (n = 379) in an institutional review board-approved, multicenter, randomized parallel group trial completed the short form of the CLDEQ-8, and anchoring question on overall opinion of SCLs, and other questionnaires at baseline and 2 weeks after randomization to daily wear of either senofilcon A or lotrafilcon B silicone hydrogel lenses (Table 1). In this validation phase, subjects were allowed to continue to use their habitual care system (if appropriate) with the following distribution: OPTI-FREE RepleniSH 31%, ReNu MPDS 17%, OPTI-FREE EXPRESS MPDS 11%, and Clear Care 11%. Thirty percent (30%) of subjects were not using an appropriate care system (saline only or unknown system) and were given COMPLETE Multipurpose lens care kits at the baseline visit.
Change in overall opinion was measured by comparing the overall opinion rating (“Which statement best describes your overall opinion of your current contact lenses?” with response options of Poor, Fair, Good, Very Good, and Excellent) of habitual lenses to lenses to which the subject was randomized in the trial. For example, change in a worse direction would exist if the subject reported Very Good with habitual lenses and Good with new lenses. Change in assessment by two steps was considered “Much Worse” if it was in the worsening direction and “Much Better” if there were two levels of improvement in the overall opinion.
Only subjects with complete data sets (n = 309) were included in this analysis. Summed CLDEQ-8 scores (possible 0–37) were tested for correlation with overall opinion of habitual lenses (Spearman's rank correlation coefficient) and then for responsiveness to change in overall opinion after randomization by ANOVA. Statistical significance was assumed if p < 0.05.
Table 2 shows the demographics of the subject sample in each phase of the research and the distribution of habitual SCLs and care systems for subjects in each phase. Note that habitual lens care system was not queried in the item reduction phase of the research.
Item Reduction Phase
A number of CLDEQ questions were significantly correlated with overall opinion of contact lenses, with more questions showing significant correlations at visits after randomization than at baseline. Correlations between individual CLDEQ symptom questions at all visits are listed in Table 3.
Ranking of these correlations was used to model the best mix of questions for the short form of the CLDEQ. A strategy that chose questions with the highest correlations and highest proportions of significant correlations was put into a sequence that was then tested to reduce redundancy. Some questions, such as burning/stinging, showed very high statistically significant correlations with other items that also had high correlation to overall opinion. Those questions were eliminated from the final CLDEQ-8 short form, as they did not affect the overall performance of the instrument's ability to discriminate by the wearer's overall opinion of the SCLs they were wearing at that visit. The CLDEQ-8 questions are shown in Fig. 1.
Known Groups Validity Phase
Fig. 2 shows the mean and distribution of CLDEQ-8 scores by overall opinion of habitual lenses at baseline for the known groups validity phase. The distribution of CLDEQ-8 scores by overall opinion of lenses was as follows: Fair: 17.4 ± 8.7, Good: 13.7 ± 6.4, Very Good: 9.1 ± 4.7, and Excellent: 6.4 ± 3.7, and the overall distribution was significant (ANOVA, F = 291.1, p < 0.001). There were no subjects who reported Poor overall opinion at baseline.
The distribution of change in overall opinion by change in CLDEQ-8 score is shown in Fig. 3. Note that a lower CLDEQ-8 score indicates fewer symptoms and less need for coping actions. In general, the 73 subjects who reported a worse overall opinion status had an 8.5 ± 5.8 point increase in the CLDEQ-8, the 218 in the unchanged group had a decrease of −2.3 ± 5.0 points, and the 11 subjects with improved status had a change of −16.7 ± 10.0 points in CLDEQ-8 scores. The distribution was significantly related to change in overall opinion of SCLs (ANOVA, F = 16.5, p < 0.001).
Although numerous questionnaires have been developed to assess dry eye symptoms without contact lens use,22–25 and others to assess quality of life across refractive correction,25–29 the CLDEQ is one that was developed to assess dry eye symptoms among contact lens wearers in particular. A population-specific SCL questionnaire is required because SCL wearers report a distinctly different pattern of symptoms compared with people who do not wear SCLs.16 For example, in an age-matched sample of SCL wearers and non-wearers, more than twice as many SCL wearers reported intense dryness, especially late in the day, but these symptoms were nearly eliminated when they removed lenses.4 In that study, symptom patterns also differed between SCL wearers and age-matched non-wearers; in SCL wearers, dryness intensity was not correlated with gender although it was inversely correlated with age among contact lens wearers, differing significantly from the pattern among non-lens wearers in which females and older patients report more dryness.
Because SCL-related dryness is not a disease, we developed a responsive tool to measure its recovery. The CLDEQ-8 was able to reflect improvement and worsening of overall opinion after randomization to new lenses. The SCL wearer's opinion can change after refitting with new lens designs, materials, lens care products, and with new replacement schedules; thus, the score to reflect that opinion should be developed by methods that sample patients' symptoms during the refitting process.
The CLDEQ-8 is a short form of the CLDEQ questionnaire that was designed to describe symptoms among SCL wearers. The short form was developed by selecting items that related to the wearer's global opinion of the SCLs they were wearing across all study visits. The number of items was then reduced to avoid redundancy owing to very high inter-item correlation. The eight remaining items were also capable of reflecting change in this opinion after randomization to new lens brands in the second phase of the study. Scores from an earlier short CLDEQ version relied on the response to the question “Do you think you have dry eye?,” which was useful as a stratifying question in dry eye patients without SCL wear.30 Reliance on the Gestalt “Do you think you have dry eye?” question may not be a good approach with SCL wearers, as many of them have few symptoms while not wearing lenses.4 Therefore, SCL wearers with dry eye complaints may not globally consider themselves to have dry eye separately from SCL wear. The overall opinion question used in this study focuses on the SCLs and not on the patient's underlying condition of eye dryness. In addition, the earlier short CLDEQ formula was less intuitive and possibly more cumbersome for clinician users to implement.
The CLDEQ-8 score shows an excellent dose–response relationship to the subjects' overall opinion of SCLs, making it a potentially useful tool for capturing the patient-reported opinion of new SCL treatments. There was a slight dampening of linearity in the scale when we related it to change in opinion after refitting with new lenses. Subjects showed larger change in score when they reported an improvement in overall opinion (mean decrease of 16.7 points) compared with when they had a lower overall opinion of the new lenses (mean increase of 8.5 points). Other researchers have shown that the structure of the DEQ questions showed linearity by Rasch analysis.31 In this sample, we were unable to assess the lowest end of the scale, as none of the subjects presenting for the clinical trial had an estimation of “Poor” for their habitual SCLs. Contact lens-related dryness differs from dry eye disease (fortunately for the lens wearers) in that the patient is able to cease wear if the lenses are so uncomfortable that they would warrant a poor rating. Inability to test that end of the scale is a limitation in the development of the instrument. Repeatability of the instrument should also be established in other patient populations in the future.
For diagnostic use and categorization, a valid and useful instrument must be able to distinguish between groups that are otherwise identifying themselves as different, a feature referred to as having construct validity. The items in the CLDEQ-8 were selected from the ocular surface symptoms, environmental triggers, and coping items in the longer CLDEQ questionnaire. Also, the selection was based on patient opinion of SCLs after changes between marketed lens brands, so the CLDEQ-8 is scaled to perform well to reflect changes of a magnitude that are clinically achievable through change in available products.
Ideally, we would like to understand the underlying biological basis of SCL-related dryness symptoms and have means of measuring those specific factors. However, with or without that basic understanding, a gold standard, or highly repeatable clinical tests, it remains important to be able to measure symptoms as assessed by individual SCL wearers in the clinical or clinical trial setting. The CLDEQ-8 allows a standardized quick means to measure this symptom-based condition from the wearer's point of view. Note that two vision (frequency and late day intensity) and two coping (removing lenses early and closing eyes for relief) questions are included in the CLDEQ-8 but were not the most discriminating questions in the short form of the DEQ-5.21 With SCL wear, the prelens tear film is significantly less stable with SCLs compared with the precorneal tear film in patients without SCLs32,33; therefore, changeable blurry vision has been cited as a more prominent symptom in the SCL population. Blurry vision that clears with a blink is the third most common symptom among SCL wearers, close behind discomfort and dryness. This complaint of transient blurry vision most likely stems from the tear break up that occurs between blinks in SCL wearers.34 This recent study of blinking patterns during different cognitive tasks with and without SCL wear showed that the unstable prelens tear film, and symptoms associated with it, drove an increase in blink frequency during SCL wear compared with no wear.
The two coping questions included in the CLDEQ-8, the need to close the eyes and early lens removal, capture the wearer's struggle with uncomfortable lenses. Subjects in this study with lowest overall opinion of SCLs were more likely to frequently close their eyes for a prolonged time or to finally capitulate and remove lenses before the desired time. It is clear that these symptoms alter the SCL-wearing experience and reflect a significant impact on the wearers who experience them.
In this study, we validated the eight-item short form of the CLDEQ as a means of testing the SCL wearer's symptom-related experience with their contact lenses. The sum of scores for the eight items was significantly related to overall opinion of lenses and was also able to reflect change in overall opinion in prospective treatment trials. The CLDEQ-8 will be useful for identification of SCL wearers who may benefit from lenses or lens care products designed to reduce symptoms of dryness with SCL wear and to track their progress in treatment trials.
Robin L. Chalmers
Clinical Trial Consultant
2097 East Lake Road
Atlanta, Georgia 30307
This study was funded by Johnson & Johnson Vision Care, Inc., and designed by RLC, CGB, and KM. We thank Graeme Young, PhD, MPhil, FCOptom, DipCL, FAAO, and Chris Hunt, MSc, and the staff at Visioncare Research for their assistance in fielding the CLDEQ-8 in the Known Groups Validity Phase.
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