The nonspecific umbrella term of “sensitive eyes” (SEs) is often used by patients to describe their ocular experience. This term may be used to either report symptoms or as a general description of their eyes’ susceptibility to problems. Eye sensitivity could be analogous to “sensitive skin” or “sensitive teeth,” both of which are recognized as specific medical entities.1,2 Sensitive skin, for instance, is characterized by subjective complaints of irritation without visible clinical signs,3 whereas in cases of tooth sensitivity, patients often report localized pain accompanied by relevant histological and clinical findings.4,5
The scale and nature of eye sensitivity, however, have not previously been investigated and therefore the clinical significance of this complaint remains unclear. In addition to knowing the prevalence of this entity, it would be useful for clinicians to gain some insight into the type and the extent of symptoms experienced by patients reporting SEs. Of equal importance is to understand the etiology of this sensation and whether it is linked to ocular signs, most notably hyperemia and corneal staining.
Eye sensitivity is of particular importance for contact lens (CL) wearers. This complaint might, for example, underlie hypersensitivity to stresses such as hypoxia, desiccation, or mechanical pressures because CL wearers often experience altered ocular physiology6,7 that could cause patients to report “sensitivity” in their eyes. Corneal staining, for instance, is increased with CL wear, and patients with corneal staining frequently describe symptoms of dryness or discomfort.8–10
Silicone hydrogel lenses have been reported to alleviate a number of common ocular surface symptoms and signs.11–14 The properties of different types of silicone hydrogel lenses, however, can further affect lens performance.15,16 Senofilcon A (senA) lenses, for example, have been shown to improve symptoms such as dryness and irritation,17,18 and they have been associated with reduced corneal staining.18
In this retrospective analysis, we estimated the prevalence of self-reported eye sensitivity in soft CL wearers. We also evaluated the characteristics of patients with self-reported SEs and investigated the effect of refitting a proportion of these patients with senA lenses on key symptoms and signs.
This analysis was conducted in two parts. In part 1, a database of 2154 existing soft CL wearers was used to estimate the prevalence of patients reporting eye sensitivity and to determine their characteristics. Patients included in this analysis had participated in a number of multisite clinical trials that followed a similar protocol, included similar entry criteria, and took place in sites across North America and Singapore. On entering the studies, patients reported symptoms experienced with their habitual CLs using questionnaires, and they were asked about their typical average wearing time and (AWT) comfortable wearing time (CWT). Subjective and objective refraction, visual acuity, and biomicroscopy (including grading of limbal and bulbar hyperemia, corneal staining, and other slit lamp findings) were completed at the baseline visit. Patients who responded to the question “How would you describe the sensitivity of your eyes?” were included in this analysis. Based on their response in the questionnaire, CL wearers were categorized as SE or non-SE patients. Those describing their eyes as “sensitive” or “very sensitive” were classified as SE patients, and the prevalence of key symptoms and signs was compared between the two populations.
Part 2 examined the effect of senA lenses (ACUVUE OASYS Brand Contact Lens; Johnson & Johnson Vision Care, Inc., Jacksonville, Fla) on SE patients. Of the 1122 patients who enrolled in North American sites and participated in studies that involved refitting with new lenses, 128 patients reported “sensitive” or “very sensitive” eyes with their habitual CLs. Sixty-three of them had been randomized into senA lenses, and the remainder 65 were randomized into a number of other CLs (non-senA): lotrafilcon B (n = 22) (AIR OPTIX Aqua; CIBA Vision), omafilcon A (n = 14) (Proclear Compatibles; CooperVision), and balafilcon A (n = 29) (PureVision; Bausch & Lomb). The clinical performance of these lenses was assessed 2 weeks after refitting. During this period, patients used the lenses for daily wear and their habitual lens care products to store them during the night. Ultrasonic and enzymatic cleaners, however, could not be used, and patients who were using these solutions were provided with the COMPLETE Multi-Purpose Solution (Abbott Medical Optics Inc.). To prevent bias, patients were masked to the type of the new lens and in most trials were not aware of the study sponsor. Patients were compensated for their time.
All studies were conducted according to the Declaration of Helsinki. Ethics approvals had been gained from local institutional review boards before each study, and patients provided written consent.
Patients included in this analysis were existing daily soft CL wearers free of ocular abnormality or disease that would contraindicate CL wear. If present, corneal fluorescein staining was required to be equal to or lower than grade 2 staining in any quadrant. Patients who had worn their habitual lenses for less than 4 weeks before enrollment were excluded. To be eligible, patients were required to be aged between 18 and 45 years and to have a spherical refractive CL prescription between −1.00 and −6.00 diopters (D).
In the first part of this analysis, data on a number of outcomes were compared between SE and non-SE patients to define the clinical characteristics of the SE population. The second part compared senA with habitual lenses and the performance of senA at 2 weeks versus the performance of lenses of different material and/or design. In the latter case, because the individual numbers of lotrafilcon B, omafilcon A, and balafilcon A lenses were not large enough, they were grouped together as an non-senA arm.
Statistical analysis was performed using the Student t test, Wilcoxon rank sum test, Mann Whitney U test, or Pearson χ 2 test, depending on the nature of the variable under test using the SPSS software (version 19, IBM). A value of p ≤ 0.05 was considered statistically significant.
Prevalence of SEs in Soft CL Wearers
Of the of 2154 CL wearers, 265 (12.3 ± 1.3%) reported “sensitive” or “very sensitive” eyes with their habitual CLs and were therefore characterized as “SE patients” for the remaining analysis (Fig. 1). Although the remainder of lens wearers were considered as “non-SE patients,” approximately 38% (727 of 1889) of them described their eyes as “slightly sensitive,” indicating that a substantial proportion of the current clinically normal soft CL wearers experience some degree of eye sensitivity.
Characteristics of SE Patients
To gain insight into the characteristics of the SE population, the demographics and biometric data of SE and non-SE patients were compared (Table 1). No significant differences were observed in sex or age between the two populations. Approximately 69% of patients in both populations were females, and the mean age was 28.3 ± 6.4 years and 27.9 ± 6.3 years in SE and non-SE patients, respectively. Mean sphere refraction (SE vs non-SE patients: −3.36 ± 1.49 D vs −3.21 ± 1.43 D, p = 0.12), cylinder refraction (−0.28 ± 0.32 D vs −0.25 ± 0.28 D, p = 0.21), and horizontal keratometric reading (−43.75 ± 1.38 D vs −43.74 ± 1.42 D, p = 0.88) were similar between SE and non-SE patients, suggesting that this sensation is independent of the patient’s prescription. Visual acuity with habitual spectacles (0.01 ± 0.08 logMAR vs 0.00 ± 0.07 logMAR, p = 0.01) or habitual CLs (−0.01 ± 0.06 logMAR vs −0.02 ± 0.06 logMAR, p = 0.02) was significantly worse in the SE group, although the mean differences were only equivalent to one-half of one letter.
Patient responses to questions regarding symptoms experienced “frequently” or “constantly” with their habitual lenses were compared between the SE and non-SE populations. The most common symptoms in both populations were dryness followed by irritation, and these were twice as common in the SE population (Fig. 2). The prevalence of dryness was 43 and 19% in the SE and non-SE patients (p < 0.0001), respectively, and the equivalent percentages for irritation were 23 and 11% (p < 0.0001). Approximately 19% of the SE patients reported redness and 5% stinging, whereas the equivalent percentages for the non-SE patients were 6% (p < 0.0001) and 1% (p < 0.0001), respectively (Fig. 2). When considering any of these symptoms, approximately 45% of the SE patients experienced at least one of them (data not shown).
Patients were also asked about their typical AWT and CWT (Fig. 3). Mean AWT was approximately 1 hour shorter in the SE patients in comparison with that in the non-SE patients (p < 0.0001) (Fig. 3A). The equivalent difference in mean CWT, however, was almost 2 hours (SE vs non-SE patients, 10.6 vs 12.2 hours, p < 0.001), suggesting that a proportion of the SE patients continue wearing their lenses, although they do not “feel comfortable” (Fig. 3A). To gain further insight into the wearing times of the SE population, our findings were plotted as cumulative frequency of CWT (Fig. 3B). Of non-SE patients, 86% reported that their lenses felt comfortable after 11 hours of wear, whereas the equivalent proportion in SE patients was approximately 67% (p = 0.002). The difference in the proportion of patients reporting CWT of up to 15 hours per day between the two populations was still substantial (15 vs 28%), although it was not statistically significant (p = 0.18). Together, these data suggest that SE patients experience symptoms more frequently than “normal” lens wearers, and this could affect their CWT.
Because CL age can impact its performance, the period that habitual lenses had been worn before the study was examined. Although SE patients wore their lenses for approximately 3 days longer, on average, in comparison with non-SE patients, the difference between the two groups was not statistically significant (20.1 vs 16.8 days, p = 0.32) (data not shown).
The qualifying criteria for “clinically relevant” signs are described in Table 2. No significant differences between the SE and non-SE populations were observed in the numbers of patients with clinically relevant corneal staining (≥3 on a 0 to 15 scale) nor conjunctival injection or staining (≥2 on a 0 to 4 scale) (Fig. 4). Approximately 15% of patients in both populations showed clinically relevant corneal staining, 35% conjunctival staining, and 10% bulbar or limbal hyperemia. Additional signs, including corneal edema, neovascularization, and tarsal abnormalities, were also equivalent between the two populations (data not shown).
Riley et al.18 have previously described a population of “problem” patients, which represents approximately one-half of the soft CL wearers, composed of patients experiencing dryness, irritation, reduced CWT, or compromised ocular physiology (Table 3). Using a similar approach, we sought to estimate the prevalence of problem patients in the SE and non-SE populations. Forty-six percent of the non-SE patients qualified for at least one of the criteria described in Table 3. This proportion is equivalent to the prevalence of problem patients reported in the Riley et al.18 study. The prevalence of problem patients within the SE population, however, was significantly higher (73%, p < 0.0001) in comparison with the non-SE group, indicating that most SE patients could be regarded as a subpopulation of problem patients who experience a broader spectrum of more frequent symptoms (Fig. 5).
Effect of Refitting SE Patients with SenA Lenses
The mean frequency of dryness, discomfort, redness, and stinging was found to be significantly lower with senA in comparison with habitual lenses (Fig. 6A). For example, only 20% of the SE patients reported that they “never” experience dryness with their habitual lenses, whereas after refitting with senA lenses, this proportion was increased to 44% (p = 0.0003). Likewise, senA decreased the numbers of patients reporting irritation, as approximately 25% of the SE patients who complained about some degree of irritation with their habitual lenses reported that they “never” experienced this symptom with senA lenses (p = 0.015). Similar findings were observed for redness (p = 0.009) and stinging (p = 0.012).
Mean CWT was increased by approximately 1 hour per day after refitting with senA lenses, but this difference was not statistically significant (p = 0.11) (data not shown). The effect of senA lenses on CWT, however, is more evident in the cumulative frequency representation of findings (Fig. 6B). The proportion of patients reporting CWT of 8 to 12 hours was significantly higher with senA lenses in comparison with those wearing habitual lenses (p = 0.037).
To examine whether this reduction in the frequency of symptoms after refitting with senA lenses is reflected in the clinical appearance of the eye, a number of signs were considered (Table 4). Limbal hyperemia was significantly reduced with senA lenses (0.62 vs 0.29 scale 0 to 4, p = 0.001). No significant differences in the grade of bulbar hyperemia, tarsal abnormalities, and corneal staining or edema were observed between the baseline and follow-up visits. The proportion of patients with clinically relevant signs did not change significantly between the two visits (p = 0.64) (data not shown).
The effect of senA lenses on symptoms and signs was also compared with a group using non- senA silicone hydrogel lenses. No significant differences were detected between the two arms on entering the trials (Table 5). Two weeks later, however, in the non-senA arm, the values on a 0 to 3 scale (0, never; 1, infrequently; 2, frequently; 3, constantly) for the frequency of dryness, irritation, and stinging were 1.02, 1.16, and 0.53, respectively; whereas in the senA arm, these values were 0.64 (p = 0.0056), 0.72 (p = 0.0015), and 0.18 (p = 0.0049). No significant differences between the two arms were noticed at this time point in patient reported redness (p = 0.27), limbal hyperemia (p = 0.93), bulbar hyperemia (p = 0.41), and corneal staining (p = 0.20).
The term “sensitive eyes” is not well defined but usually refers to an exaggerated and unpleasant sensation that patients experience. The findings of this study suggest that this sensation in CL wearers is associated with a relatively high prevalence of additional common symptoms that are not reflected in clinical signs. This study showed that approximately one in eight CL wearers regard their eyes as sensitive. This is a smaller group in comparison with those reporting significant CL-related symptoms, whereas some SE patients do not report any symptoms. Furthermore, unpublished market data suggest that SEs are also reported by patients who have not used CL as a treatment option for their refraction, supporting the notion that eye sensitivity is a more generalized sensation that is not limited to CL wearers. The entity of “eye sensitivity” could be regarded as being analogous to conditions of skin sensitivity, where subjective patient complaints are not accompanied by obvious signs of irritation or inflammation, although, in some cases, findings such as thinning of the outer epidermal layer have been reported.1,3,19 Indeed, patients with sensitive skin often describe dermatological symptoms of dryness, redness, and stinging,19,20 which were also reported in eyes of a substantial proportion of SE patients. Although symptoms were reported in different tissues and their causes in the two tissues are not likely to be related, this similarity between the two populations is indicative of the sensations that patients include under the umbrella term of “sensitivity.” Teeth sensitivity, on the other hand, seems to be a distinct pathology characterized by pain or discomfort in response to stimuli generally accompanied by relevant histological findings.21
The proportion of SE patients experiencing common symptoms is higher than the proportion of “normal” lens wearers reporting such symptoms. Our results show, for example, that 43% of SE patients experience dryness “frequently” or “constantly,” whereas previous studies that used a similar approach to estimate the prevalence of dryness have reported a lower number.22–25 A large study of approximately 900 participants found that 29% of soft CL wearers experienced dryness symptoms,22 whereas other studies have shown even lower percentages.23–25 This indicates that patients with eye sensitivity, as described in the current analysis, could be considered as a separate subset of CL wearers characterized by a higher prevalence of key symptoms. This hypothesis is supported further by comparing our results with findings of a study by Riley et al.,18 which suggested that approximately 50% of CL wearers experience compromised ocular physiology, symptoms of discomfort, or reduced CWT, and they could therefore be regarded as “problem” or “marginally successful” patients. The equivalent proportion in SE patients within our analysis was 73%. The numbers of patients with clinical signs, however, were similar between the two studies, suggesting that it is the higher prevalence of symptoms, not biomicrospic signs, that distinguishes SE patients from problem CL wearers described in other studies.
Key symptoms, such as dryness and discomfort, have long been believed to be the most common reasons for discontinuing CLs.26–28 Because the prevalence of these symptoms is high in the SE population, it could be suggested that SE patients are more prone to discontinuing CL wear in comparison with non-SE or “normal” patients. This hypothesis could be further supported by the fact that practitioner’s misjudgment, for example, using an inappropriate lens design or failing to diagnose solution-related reactions, is considered one of the most important reasons for CL dropout.28 Indeed, the mismatch between symptoms and clinical signs observed in SE patients could be misleading for eye care practitioners, preventing them from properly evaluating the patient’s condition and subsequently from taking the appropriate actions.
This lack of agreement between symptoms and signs was also observed after refitting SE patients with senA lenses. Our results show that refitting with senA lens improved dryness, irritation, self-reported redness, and stinging, although its effect on clinical signs was only minimal. Decreased intensity of limbal hyperemia after refitting with senA lens may be related to the modulus or the relatively high Dk of this lens. This is supported by studies connecting high Dk lenses with reduced hyperemia.14,29 Improvement in symptoms, such as irritation, is likely to be associated with reduced friction because of the lens’ relatively high lubricity.30 Symptoms of discomfort have also been shown to be related to poor lens fit.31 However, because information on the habitual lens fit was not captured in the studies included in this analysis, the hypothesis that improvement in some symptoms was in part caused by better fitting with senA lenses could not be investigated. To rule out the possibility that the improvement in symptoms after refitting with senA lenses was caused by a placebo or a Hawthorne effect, we compared the efficiency of senA lenses against a non-senA arm, and our results showed that senA lenses were significantly more efficient in improving a number of symptoms. Future prospective studies, however, that will recruit SE patients and will have enough power to examine the head-to-head effect of different lens materials and/or designs are required to explore this issue further. An additional potential limitation of this retrospective analysis could be that it monitored the performance of senA lenses for only 2 weeks, and it is therefore impossible to know whether the superiority of this lens over habitual or non-senA lenses will be maintained for a longer period.
The proportion of patients reporting CWT of 8 to 12 hours was significantly higher with senA lenses in comparison with those using habitual lenses, suggesting that refitting helped patients to wear their lenses functionally, as wearing CLs between 8 and 12 hours is usually required during an average work day. No significant differences, however, were noticed before and after fitting with senA lenses in the numbers of patients reporting CWT of less than 7 or more than 13 hours per day. This could be related to the fact that relatively short or extended periods of CWT may reflect patients dissatisfied with their CL experience or well-adapted wearers, respectively. Dissatisfied patients might find it more difficult and possibly need more time to experience a significant improvement in comfort. On the other hand, a potential increase in the CWT of well-adapted patients would not be expected to be substantial because these patients usually wear their lenses comfortably for up to 18 hours per day.
The low intensity of signs in relation to the high prevalence of symptoms in SE patients may be explained in part by cases where damage or irritation to the ocular surface has not become visible at the time of examination despite its potential association with symptoms. Subclinical inflammation, for instance, has been reported previously in soft CL wearers with symptoms of dryness or discomfort,32 and a subclinical increase in epithelial permeability has been observed in CL wearers without signs of hypoxia.33 An alternative explanation for this lack of agreement between symptoms and signs could be that the techniques used in the studies included in this analysis were not able to capture subclinical irritation. In vivo confocal microscopy, for example, may reveal CL wear–related corneal changes possibly not detectable by slit lamp examination.34
In conclusion, we suggest that a substantial proportion of CL wearers report SEs with their habitual lenses. This group of patients is characterized by a high prevalence of additional symptoms, which are not accompanied by an equivalent increase in clinical signs. The reporting of SEs correlates with the number of symptoms that usually interfere with CL wear, and therefore, close questioning and examination of these patients could improve their CL experience and possibly the rate of CL dropouts. Careful choice of CL material and design could help reduce these symptoms.
Vistakon, Johnson & Johnson Vision Care Inc.
7500 Centurion Parkway
Jacksonville, Florida 32256
M.S., C.H., and G.Y. have received payment from Vistakon (Johnson & Johnson Vision Care, Inc.) to conduct this research. S.H.-C. is an employee of Vistakon (Johnson & Johnson Vision Care, Inc.).
Part of this study was presented as a poster at the Annual Congress of the American Academy of Optometry in 2011 and at the Congress of the British Contact Lens Association in 2012.
Received May 5, 2012; accepted August 14, 2012.
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Keywords:© 2012 American Academy of Optometry
contact lens; sensitivity; symptoms; signs; senofilcon A