Fig. 1 depicts the frequency of ocular symptoms among contact lens wearers in this study. For purposes of illustration, the symptoms in Fig. 1 are ranked from highest mean frequency (Fig. 1a : dryness) to lowest mean frequency (Fig. 1e : soreness). The symptoms of scratchiness and irritation and light sensitivity had identical mean frequencies, but the former was listed first. The symptom that ranked second in mean frequency was blurry, changeable vision (Fig. 1b). The most common response for both dryness (Fig. 1a) and blurry, changeable vision (Fig. 1b) was to mark nearest “infrequently” on the analog scale. The most common response for the other three symptoms was closer to the word “never” on the analog scale.
The severity of ocular symptoms is illustrated in Fig. 2. Symptoms are ranked by mean severity for illustrative purposes, but Figs. 2a and 2b have the same mean severities, as do 2c and 2d. In all cases, the most common response was to mark closest to the word “never” on the analog scale. As Fig. 2 shows, very few subjects found the symptoms noticeable enough to remove their contact lenses. Interestingly, although dryness was the most frequent symptom (Fig. 1a), it was not the most noticeable (Fig. 2d). On average, scratchiness and irritation (Fig. 2a) and blurry, changeable vision (Fig. 2b) were more irritating and noticeable symptoms than dryness. Eye soreness was the least frequent (Fig. 1e) and least noticeable (Fig. 2e) symptom among those queried.
Fig. 3 compares morning (or within 2 h after lens insertion) and evening (or within 2 h before lens removal) symptoms. In Fig. 3a, there is a shift toward increasing discomfort in the evening compared with the morning. In the morning, the majority of subjects marked close to “excellent” on the analog scale, whereas the most common response in the evening was “good.” In the evening, 19% of subjects marked in the “not great” and “terrible” range, compared with only 3% in the morning. The difference between morning and evening comfort ratings was statistically significant (p < 0.00001, paired t-test). When the comfort of right and left eyes were compared, there was no statistically significant difference between eyes.
There was also a shift toward increasing dryness from morning to evening (Fig. 3b). In the morning, the most common response was closest to the words “not dry at all” on the analog scale, while “a little dry” was the most common response in the evening. Sixteen percent of subjects marked from “pretty dry” to “extremely dry” in the evening, as compared to only 4% in the morning. The difference between dryness ratings in the morning and evening was statistically significant (p < 0.0.0001, paired t-test). In addition, there was a statistically significant (p = 0.001, paired t-test) shift toward more frequent evening symptoms of blurry, changeable vision compared with in the morning (Fig. 3c).
Fig. 4 compares the symptoms of dryness with and without contact lenses. As Fig. 4a illustrates, dryness was a significantly more frequent symptom while wearing contact lenses than without them (p < 0.00001, paired t-test). The most common response while wearing contact lenses was to mark closest to the word “infrequently,” but most respondents marked closest to the word “never” while not wearing their contact lenses. In addition, 15 subjects reported dryness as a frequent or constant occurrence while wearing their contact lenses, compared with only four subjects without their contact lenses. As Fig. 4b shows, there was also a significant difference in the reported severity of dryness with and without contact lenses (p < 0.00001, paired t-test). Although most subjects marked closest to “never have the feeling,” more subjects reported that dryness was a noticeable symptom with contact lenses. However, very few found dryness noticeable or irritating enough to remove their contact lenses. Eye dryness did not seem to interfere much with daily activities in this group of subjects (Fig. 4c). However, there was a statistically significant difference in reported interference of dryness with daily activities while wearing contact lenses compared with without contact lenses (p < 0.00001, paired t-test).
Eighty-four percent of subjects reported wearing their lenses at least 5 to 7 days/week and more than 9 h per work day. These wearing times indicate that the majority of subjects should be considered successful contact lens wearers. When asked about the percent of time they used a computer during workdays, the mean response was 39 ± 30%. Reported computer usage declined on the nonwork days to 8 ± 11% of the time.
Twenty-four percent of patients reported systemic medication usage, with oral contraceptives (7%), blood pressure medications (11%), and antidepressants listed (7%) as the most commonly used medications. Six subjects reported using multiple medications. Thirty-five percent of subjects reported having allergies, but only 15% took oral medications or used eye drops for allergies. Approximately one third (30%) of subjects reported dryness of other mucous membranes (nose, mouth, or vagina). Seventeen percent of subjects used contact lens rewetting drops, but other dry eye treatments were less commonly reported.
The questionnaire also asked subjects how much they were helped by dry eye treatments, using an analog scale that spanned from “complete cure” (0%) to “no help at all” (100%). On average, subjects marked closest to the words “very helpful” (43 ± 15% of analog scale). Twenty (24%) subjects reported using artificial tears or contact lens rewetting drops one to three times per day and 22 (27%) reported using one or two bottles per month. When asked how much money was spent per month on contact lens rewetting drops or artificial tears, 17 (20%) of subjects reported spending $5.00 Canadian or less, 4 (5%) reported $6.00–10.00, and 1 (1%) reported $11.00–20.00.
Twenty-four (30%) of subjects answered “yes” to the question, “Do you think you have dry eye?” Compared with subjects answering “no” to this question, subjects who thought they had dry eye reported significantly increased symptoms (p < 0.05); unpaired t-tests) for all questions listed in Table 1 (except morning and evening blurry, changeable vision). Sixteen (67%) subjects who thought they had dry eye also reported that they had been told previously that they had dry eye.
Many of the symptom questions were significantly correlated (Table 2). For example, correlations between morning and evening comfort (questions 8 and 9), evening comfort and the frequency of dryness (questions 9 and 10a), and the frequency of scratchiness, irritation, and soreness (11a and 12a) were high (r ≥ 0.61). Morning and evening comfort (questions 8 and 9) and morning and evening dryness (questions 10b and 10c) were also relatively highly correlated (r = 0.46 to 0.78). Morning comfort and dryness were not significantly correlated with morning blurry, changeable vision, but evening symptoms were significantly correlated. Some questions, such as evening comfort and soreness (questions 9 and 12a), showed statistical significance, but the correlations were relatively low (r = 0.28).
There was also a high correlation among questions within symptom categories, such as dryness. As Table 2 illustrates, the frequency of dryness and morning and evening dryness (questions 10a, b, and c) were highly correlated (r ≥ 0.54), as was the frequency of blurry, changeable vision with morning and evening symptoms (questions 14a, b, and c) (r ≥ 0.61). Questions concerning the severity of symptoms or how much the symptoms interfere with daily life are not represented in Table 2. However, within symptom categories, there was a high correlation between frequency and severity questions (r = 0.60 to 0.86), frequency and interference questions (r = 0.71 to 0.80), and severity and interference questions (r = 0.73 to 0.81).
Many of the contact lens wearers in this study experienced the symptoms of eye dryness, scratchiness and irritation, light sensitivity, soreness, and blurry or changeable vision, some on a frequent basis. Yet, this was a group of relatively successful full-time contact lens wearers. Most subjects wore their lenses more than 9 h per day and 5 days per week. Only contact lens wearers were asked to fill out this pilot questionnaire, so it is not surprising that when asked about the severity of ocular symptoms, most did not report that their symptoms merited lens removal or caused them to stop work or hobbies.
These results are in agreement with those of a previous study, in which dryness was the most frequent symptom reported among contact lens wearers. 4 In this study, the majority of subjects reported dryness as an “infrequent” to “frequent” symptom, and scratchiness and irritation as an “infrequent” symptom (Figs. 1a and c). In addition, light sensitivity and eye soreness were not experienced by most subjects in our study (Figs. 1d and e).
As Figs. 3a and b show, there was a large difference between morning and evening symptoms of comfort and dryness. The majority described their lenses as “not dry” or of “excellent” comfort in the morning, but most described their lenses as at least “a little dry” with only “good” comfort in the evening. Approximately 20% of subjects described their lens comfort as “not great” or “terrible” in the evening. The reason for the increase in the feeling of dryness and discomfort throughout the day is unknown. It may be because of deposit formation over the course of a day, which renders the lens surface increasingly hydrophobic. 18 Decreased blinking connected with extensive near work may also cause a worsening of dry eye symptoms toward the end of the day. Subjects in this study reported that they used a computer an average 39% of the time during workdays. Video display terminal usage is known to decrease blinking and is often connected to dry eye symptoms. 19–21
Foggy, changeable, or blurry vision that clears up temporarily with a blink was also a frequent symptom (Fig. 1b). The majority of subjects ranked it as an “infrequent” occurrence that was not noticeable enough for them to remove their contact lenses (Fig. 2b). There was also a significant diurnal shift toward more frequent blurry, changeable vision in the evening (Fig. 3c). We asked about these visual changes because they are often described in our clinical practice by contact lens wearers who have other dry eye symptoms. Previous studies show that tear film disruption causes loss of optical quality, visual acuity, and contrast loss 22–24 with and without contact lenses. Patients with symptoms of dry eye usually show a decreased tear film break-up time 15 and, therefore, may be likely to report visual disturbances caused by poor tear film quality. 18 Visual disturbances have been reported as a symptom of dry eye patients who do not wear contact lenses. 6, 25, 26 In a recent Japanese study that included contact lens wearers, the most commonly reported symptoms included blurred vision. 27
The predominance of dryness as a frequent symptom may also explain why 50.1% of contact lens wearers thought that they had dry eye in the Canadian Dry Eye Epidemiology Study. 10 The diagnosis “dry eye” may be a term that patients easily link with the ocular sensation of dryness. Subjects in our study who responded “yes” to the question, “Do you think you have dry eye?” were significantly more symptomatic than those who responded “no.” In a Japanese study conducted by facsimile (598 participants), 33% believed that they had dry eye, but only 6.8% of the total sample had been influenced in their decision by eye care practitioners. In contrast, the majority of subjects who thought they had dry eye in our study reported a previous dry eye diagnosis. Therefore, the utility of this self-diagnosis question for separating symptomatic patients from less symptomatic patients is not clear from our data.
Our data do show that wearing contact lenses increased the symptom of ocular dryness. Subjects reported eye dryness as significantly more frequent (Fig. 4a) and severe (Fig. 4b) while wearing contact lenses than without contact lenses. Most subjects did not describe the dryness as frequent or noticeable enough to remove their contact lenses. Even though there was a significant difference in the interference of daily life between wearing contact lenses and no contact lenses, the majority did not stop work or hobbies because of the symptom of dryness (Fig. 4c). However, 35 (42%) subjects did report that dryness at least rarely interfered with work or hobbies while wearing contact lenses, whereas only 6% reported similar interference without contact lenses. This worsening of dry eye symptoms while wearing contact lenses has been suggested by others, and is presumably caused by disturbance of the tear film by placing a lens on the eye. 1, 18, 28
In this study, most of the subjects who reported using dry eye treatments, such as contact lens rewetting drops or artificial tears, found them to be “very helpful” in relieving their dry eye symptoms. However, usage of these treatments was relatively infrequent. The majority reported using contact lens rewetting drops or artificial tears only one to three times per day, purchasing one or two bottles per month, and spending $5.00 or less per month.
There were high correlations between many of the questions in this questionnaire (Table 2). For example, the symptoms of comfort, dryness, and scratchiness and irritation were highly correlated, as well as scratchiness and irritation and eye soreness. There was also a relatively high correlation between light sensitivity and blurry, changeable vision. It is difficult to interpret the meaning of these and other correlations because the ocular surface sensations underlying these symptoms are poorly understood. 29 Correlations may be attributable to an overlap among the English terms we used to describe ocular symptoms, so that many symptom terms represent similar feelings. Another possibility is that symptoms are derived from ocular sensations that are linked biologically, but are dissimilar feelings. In any case, the correlation between many questions indicates that the questionnaire can be shortened to be useful as a clinical tool. Many dry eye questionnaires are shorter than ours, 5, 8, 10, 11, 26 but they have not been developed from a comprehensive base with an understanding of the possible connection between symptom questions. This pilot version of our questionnaire represents a first step in the development of a clinically useful research tool for studying dry eye symptoms.
Ocular symptoms were relatively frequent among the contact lens wearers surveyed in this study. Among the symptoms queried, the most frequent was eye dryness and the least frequent was eye soreness. Scratchiness and irritation and blurry, changeable vision were the most noticeable symptoms, but most ocular symptoms did not interfere enough with daily life to cause subjects to stop work or hobbies or remove their contact lenses. There was also a shift toward increased severity of dryness and discomfort at the end of the contact lens wearing time. These results indicate that eye care practitioners should ask about symptoms that occur later in the day or examine patients who wear contact lenses at the end of the day to better identify those who may have clinical signs associated with symptoms of dry eye.
First presented at the Association for Research and Vision in Ophthalmology meeting, May 1998.
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Keywords:© 2000 American Academy of Optometry
dry eye; questionnaires; contact lens; symptoms; tears