Journal of Refractive Surgery

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ORIGINAL ARTICLES 

A Quality of Life Comparison of People Wearing Spectacles or Contact Lenses or Having Undergone Refractive Surgery

Konrad Pesudovs, PhD; Estibaliz Garamendi, PhD; David B Elliott, PhD

Abstract

ABSTRACT

PURPOSE: To demonstrate the use of the Quality of Life Impact of Refractive Correction (QIRC) questionnaire for comparing the quality of life of pre-presbyopic individuals with refractive correction by spectacles, contact lenses, or refractive surgery.

METHODS: The 20-item QIRC questionnaire was administered to 104 spectacle wearers, 104 contact lens wearers, and 104 individuals who had undergone refractive surgery (N =312). These groups were similar for gender, ethnicity, socioeconomic status, and refractive error. The main outcome measure was QIRC overall score (scaled from 0 to 100), a measure of refractive correction related quality of life. Groups were compared for overall QIRC score and on each question by analysis of variance, adjusted for age, with post hoc significance testing (Sheffé).

RESULTS: On average, refractive surgery patients scored significantly better (mean QIRC score 50.2±6.3, F2309= 15. 18, P<.001) than contact lens wearers (46.7 ±5.5, post hoc P<.001) who were in turn significantly better than spectacle wearers (44.1 ±5. 9, post hoc P<.01). Convenience questions chiefly drove the differences between groups, although functioning, symptoms, economic concerns, heath concerns, and well being were also important. Spectacle wearers with low strength prescriptions (46. 18 ±5. 05) scored significantly better than those with medium strength prescriptions (42.74±6.08, F2 190=3.66, P<.05, post hoc P<.05). A small number (n=7, 6.7%) of refractive surgery patients experienced postoperative complications, which impacted quality of life (37.86±2.13).

CONCLUSIONS: Quality of life was lowest in spectacle wearers, particularly those with higher corrections. Contact lens wearers had significantly better QIRC score than spectacle wearers. Refractive surgery patients scored significantly better than both. However, this was accompanied by a small risk of poor quality of life due to postoperative complications. The QIRC is an effective outcome measure for quality of life impact of refractive correction. [J Refract Surg. 2006;22:19-27.]

Abstract

ABSTRACT

PURPOSE: To demonstrate the use of the Quality of Life Impact of Refractive Correction (QIRC) questionnaire for comparing the quality of life of pre-presbyopic individuals with refractive correction by spectacles, contact lenses, or refractive surgery.

METHODS: The 20-item QIRC questionnaire was administered to 104 spectacle wearers, 104 contact lens wearers, and 104 individuals who had undergone refractive surgery (N =312). These groups were similar for gender, ethnicity, socioeconomic status, and refractive error. The main outcome measure was QIRC overall score (scaled from 0 to 100), a measure of refractive correction related quality of life. Groups were compared for overall QIRC score and on each question by analysis of variance, adjusted for age, with post hoc significance testing (Sheffé).

RESULTS: On average, refractive surgery patients scored significantly better (mean QIRC score 50.2±6.3, F2309= 15. 18, P<.001) than contact lens wearers (46.7 ±5.5, post hoc P<.001) who were in turn significantly better than spectacle wearers (44.1 ±5. 9, post hoc P<.01). Convenience questions chiefly drove the differences between groups, although functioning, symptoms, economic concerns, heath concerns, and well being were also important. Spectacle wearers with low strength prescriptions (46. 18 ±5. 05) scored significantly better than those with medium strength prescriptions (42.74±6.08, F2 190=3.66, P<.05, post hoc P<.05). A small number (n=7, 6.7%) of refractive surgery patients experienced postoperative complications, which impacted quality of life (37.86±2.13).

CONCLUSIONS: Quality of life was lowest in spectacle wearers, particularly those with higher corrections. Contact lens wearers had significantly better QIRC score than spectacle wearers. Refractive surgery patients scored significantly better than both. However, this was accompanied by a small risk of poor quality of life due to postoperative complications. The QIRC is an effective outcome measure for quality of life impact of refractive correction. [J Refract Surg. 2006;22:19-27.]

The provision of refractive error correction in the United States is a $22.8 billion industry, with 59% of the US population possessing a refractive correction.1 Although spectacles dominate this market, and approximately 12% of the adult population wears contact lenses, refractive surgery is gaining ground with 6.1 million (2.2%) Americans having undergone refractive surgery, including 1.2 million (-0.4%) in 2002. 1 Demonstrating the safety and benefit of refractive surgery is critical to its acceptance and growth in the marketplace. Objective methods for demonstrating the visual and optical benefits of refractive surgery exist.23 However, there is neither an agreed method nor a movement toward routine reporting of arguably the most important refractive surgery outcome - quality of life. The purpose of this study is to demonstrate the use of a newly described refractive correction specific quality of life questionnaire for comparing spectacle wearers, contact lens wearers, and post-refractive surgery patients.

No previous studies have specifically compared the quality of life of the three modes of refractive correction. However, changes in quality of life due to refractive surgery have previously been reported using two validated questionnaires: the Refractive Status Vision Profile (RSVP)4 and the National Eye Institute Refractive Quality of Life (NEI-RQL).5 The Subjective Vision Questionnaire (SVQ) has also been conventionally validated, but not tested for its responsiveness to refractive surgery.6 Other studies that report quality of life issues before and after refractive surgery have used informal, non-validated questionnaires.7"10 However, none of these questionnaires is suitable for the purpose of comparing the quality of life among spectacle wearers, contact lens wearers, and post-refractive surgery patients. The RSVP and the National Eye Institute Visual Functioning Questionnaire (NEI-VFQ) have been shown to be insensitive to quality of life issues relevant to people wearing contact lenses.1112 Similarly, the NEI-RQL could not differentiate between spectacle and contact lens wearers although it could differentiate both from emmétropes.13

Perhaps the most important issue in questionnaire selection is the validity of the scoring system. The RSVP, NEI-RQL, and SVQ instruments all use traditional Likert scoring where patients' response scores for a selected set of questions are summed to derive the overall score.14 Likert scoring values all questions equally and therefore assumes that each question has equal importance on the scale being measured. In addition, the response categories used for each question are scored assuming uniform increments from category to category. For example, in a Likert scaled visual disability questionnaire, The Activities of Daily Vision Scale (ADVS),15 a response of "a little difficulty" (score of 4) is used to represent twice the level of ability as "extreme difficulty" (score of 2), which is similarly two times as good as "unable to perform the activity due to vision" (score of 1) for all questions. This appears illogical, and Rasch analysis has been used to confirm that differently weighted response scales are required for different questions to provide a valid scale.16 For question difficulty with the ADVS questionnaire an answer of "a little difficulty" to the question regarding visual difficulties "driving at night" scores the same as the "a little difficulty" with "driving during the day." Again, this is illogical and Rasch analysis has been used to confirm that driving at night is a more difficult task than driving during the day and Rasch analysis can provide an appropriate weighting factor for each question.16 The Rasch model is a mathematical hypothesis that the probability of a given outcome is a probabilistic function of person and item parameters. This new approach to questionnaire development using modern statistical methods, such as Rasch analysis,17"20 to measure health outcomes has suggested improved validity in question inclusion and on assessment of question importance across individual quality of life.16,21"23

Therefore, prior to comparing quality of life between the three different modes of refractive correction, we developed and validated a questionnaire, using Rasch analysis, for the measurement of the impact of refractive correction on quality of life - The Quality of Life Impact of Refractive Correction (QIRC) questionnaire.24 In the development of the QIRC questionnaire, equal numbers of completed pilot questionnaires from each mode of correction were analyzed in an effort to equalize the sensitivity of the final version to all three refractive correction types. In the following study, we determine whether the QIRC questionnaire is sensitive to quality of life issues differentially affecting people with different types of refractive correction. A quality of life instrument with such sensitivity and the superior scoring validity afforded by Rasch scaling would be the ideal outcome measure for refractive surgery.

MATERIALS AND METHODS

PATIENTS

Patients included in this study were prospectively recruited from 18 refractive surgery clinics, Optometrie practices, and contact lens specialist practices throughout the United Kingdom. The centers were chosen to provide data from rural and urban United Kingdom and with a good geographical spread to ensure the results were relevant to the UK population at large. Inclusion criteria were age between 16 and 39 years (adult pre-presbyopic age), the use of spectacles or contact lenses, or having undergone refractive surgery (LASIK, laser subepithelial keratomileusis, photorefractive keratectomy, or refractive lens implantation) between 1 month and 1 year previously. Exclusion criteria were ocular disease, ocular surgery (other than refractive), neurological or systemic disease, any medication that could alter visual function, and an inability to read and understand written English. Consecutive patients meeting the criteria were enrolled. Questionnaires were completed on site ensuring a 100% response rate. Informed consent was obtained from all patients during the interview, after the nature of the study had been fully explained. The tenets of the Declaration of Helsinki were followed and the study gained approval from the University ethical committee.

DEMOGRAPHIC DATA

Data collected from patients included age, gender, ethnicity, socioeconomic status, and self-reported strength of refractive correction. Ethnicity classification was sourced from the Compendia and Reference section of the National Statistics website.25 Socioeconomic status was classified from self-report of occupation of the primary income earner in the household on a five-category scale.26 This five-category scale is assumed to be linear so the mean group scores can be used to compare socioeconomic status. For self-reported strength of refractive correction, we asked spectacle and contact lens wearers to declare whether the strength of their refractive correction was "low," "medium," or "high." Although refractive error data would have been ideal, this was not available. Self-report of refractive status can have reasonable sensitivity and specificity especially if non-technical terms are used in the questions asked.27 According to the inclusion criteria, the population included patients with myopia, hyperopia, and astigmatism. No stratification based on type of refractive error was made. The post-refractive surgery group was also asked to report any problems with their vision or eyes that arose after their surgery.

INSTRUMENT

The development and validation of the QIRC questionnaire is reported in detail elsewhere.24 In summary, question identification and selection used literature and focus groups. Item reduction was performed by focus groups (647 questions to 90) and by administration of a pilot questionnaire. Two styles of questions were chosen: severity assessment (eg, How much difficulty do you have...?) and incidence (During the past month, how often have you experienced...?). A five-category response scale,28 with suitably spaced response labels, was selected.29 For example, for the question format "How concerned are you...?" the response labels were "not at all," "a little bit," "a moderate amount," "quite a lot," and "extremely." The 90-question pilot questionnaire was administered across settings including optometry, contact lens, and refractive surgery (mostly, but not exclusively LASIK) practices to 306 patients with 102 questionnaire responses from each mode of refractive correction. Rasch analysis was used for item reduction,30,31 which led to a 20-item questionnaire.* Rasch analysis and standard psychometric techniques demonstrated that the QIRC questionnaire is both a valid and reliable measure of refractive correction related quality of life in patients with corrected refractive error (person separation, 2.03; reliability, 0.80; root-meansquare measurement error, 3.25; mean square ± SD infit, 0.99±0.38; outfit, 1.00±0.39, item infit range 0.70 to 1.24 and item outfit range 0.78 to 1.32; unrotated factor analysis principal factor loadings 0.40 to 0.76; Cronbach's alpha 0.78; test re-test reliability intraclass correlation coefficient 0.88; and coefficient of repeatability of ±6.85 units).24 QIRC scores are reported on a 0 to 100 scale where a higher score represents a better refractive correction related quality of life. Note that the well-being items are scored in reverse order so that a higher score on all questions equates to a better quality of life. Items are well targeted to patients so that average QIRC scores are close to 50 units and the scale is free of floor and ceiling effects. Rasch analysis of the data from the validation study was used to estimate values on a linear scale for each question. These values can be used in subsequent studies, including this one where we investigated the use of QIRC for comparing the refractive correction related quality of life of patients wearing spectacles, contact lenses, or having undergone refractive surgery.

ANALYSIS

The refractive correction related quality of life among people who wear spectacles, contact lenses, and who have undergone refractive surgery was compared by overall QIRC score (main outcome measure), and on a question-by-question basis. Means were compared using one-way analysis of variance (ANOVA) with Sheffé post hoc significance testing and the statistical results were considered significant at P<.05. These statistical analyses were performed on SPSS for Windows software package vlO.l (SPSS Ine, Chicago, 111).

RESULTS

The 18 data collection centers forwarded 386 questionnaires to Bradford University. Twenty-three questionnaires were discarded due to absent demographic data or >33% missing item responses. Rasch outfit statistics identified 78 possible rogue responders and after review 42 were retained, as they appeared to provide reliable responses in a different pattern to the majority. Some of these were refractive surgery patients with postoperative complications. Thirty-six questionnaires were discarded as they appeared to provide unreliable responses. Many of them failed to note the scale reversal in the several well-being questions. This left 327 questionnaires (110 contact lens wearers, 113 spectacle wearers, and 104 refractive surgery patients). To equalize group sizes, random discarding led to a final total of 312, with 104 questionnaire responses from each refractive correction mode.

The demographic characteristics of the study population are shown in Table 1. The three groups were different for age (ANOVA, F2301=19.33, P<.001), as the refractive surgery group was significantly older (28.7±3.8 years, P<.001) than the spectacle (24.2±6.5 years) and contact lens (24.9±5.8 years) groups, which were similar to each other (P>.05). The three groups were similar for gender (approximately 69% female, chi-square P>.05), ethnicity (approximately 92% white, chi-square P>.05), and socioeconomic status (chi-squareP>.05). Socioeconomic status and ethnicity were similar to the total UK population,2526 and gender was similar to the UK population seeking eye care.32 The majority of the refractive surgery group comprised postoperative LASIK patients treated at Ultralase surgery centers in Leeds, London, Bristol, Birmingham, and Manchester using the Technolas 217 (V2 9997) excimer laser and Hansatome microkeratome (Bausch & Lomb Surgical, Rochester, NY).

Table

TABLE 1Demographic Characteristics of the Study SampleFigure 1. Columns showing mean (error bars±SD) responses for the total QIRC score by mode of refractive correction. Refractive surgery was significantly better than contact lenses (P<.01) and spectacles (P<.001). Contact lenses were significantly better than spectacles (P<.05).

TABLE 1

Demographic Characteristics of the Study Sample

Figure 1. Columns showing mean (error bars±SD) responses for the total QIRC score by mode of refractive correction. Refractive surgery was significantly better than contact lenses (P<.01) and spectacles (P<.001). Contact lenses were significantly better than spectacles (P<.05).

The three groups were significantly different in terms of overall QIRC score (F^sub 2,309^=29.29, P<.001 unadjusted; and F^sub 2,309^=15.18, P<.001 adjusted for age) (no significant interaction effect was observed and age was not a significant effect after adjusting for mode of refractive correction), with the refractive surgery group having a better QIRC score (50.23 ±6.31) than the contact lens wearers (46.70±5.49, P<.01) and the spectacle wearers (44.13±5.86, P<.001) (Fig 1). The contact lens wearers also had a better QIRC score than the spectacle wearers (P<.05). These post hoc differences were largely unaltered by adjusting for age.

To further investigate the differences between groups, each individual question was reviewed. Significant differences by ANOVA were noted between QIRC scores for the three modes of refractive correction for 18 of the 20 individual questions before adjusting for age, and 16 after adjusting for age (Fig 2). Two health concerns and two well-being questions did not detect differences between groups. Post hoc testing was then used to determine whether differences between individual groups (refractive surgery vs contact lens, refractive surgery vs spectacles, contact lens vs spectacles) were significant. After post hoc significance testing, which controlled for alpha inflation, differences between individual groups were demonstrated for 13 questions (Table 2). Only two well-being questions discriminated between groups. All five convenience questions (3-7) discriminated between groups - with refractive surgery scoring higher than one or both of the other modes on each question and contact lenses scoring higher than spectacles on two of these questions. The refractive surgery group had higher QIRC scores than both groups on "How concerned are you about the initial and ongoing cost to buy your current spectacles/contact lenses/refractive surgery?" and "How concerned are you about your vision not being as good as it could be?" The refractive surgery group had higher QIRC scores than the spectacle group on "How concerned are you about the cost of unscheduled maintenance of your spectacles/contact lenses/refractive surgery; eg, breakage, loss, new eye problems?" The refractive surgery group scored higher than the contact lens group on "During the past month, how often have you experienced your eyes feeling tired or strained?" The spectacle lens group had lower QIRC scores than both the contact lens and refractive surgery group on "How much difficulty do you have driving in glare conditions?" The contact lens group scored better than the refractive surgery group on one question: "How much trouble are your spectacles or contact lenses when you wear them when using a gym/doing keep-fit classes/circuit training etc?"

Figure 2. Columns showing mean (error bars±SD) responses on each QIRC question by mode of refractive correction (*s ign ifica nt difference by one-way ANOVA, P<.05). A) Questions 1-10. B) Questions 11-20.

Figure 2. Columns showing mean (error bars±SD) responses on each QIRC question by mode of refractive correction (*s ign ifica nt difference by one-way ANOVA, P<.05). A) Questions 1-10. B) Questions 11-20.

For the spectacle group, significant differences were noted for self-reported strength of refractive correction (F^sub 2,190^=3.66> P<.05), with post hoc testing showing the low strength refractive error group (46.18±5.05) had significantly better QIRC scores than those with medium strength refractive error (42.74±6.08, P<.05). Only 15 patients self-reported high refractive error (42. 74 ±7.48), therefore this group was not significantly different from the low strength group (P>.05). For the contactlens group, no significant difference was noted in overall QIRC score between strength of correction (F^sub 2,98^=1.37, P>.05).

A small number of refractive surgery patients optionally reported postoperative complications. Nine (8.6%) LASIK patients volunteered written comments regarding their vision postoperatively (including poor vision in low light, dry eyes, regression, and halos at night) and although their mean QIRC score was reduced compared to the average for refractive surgery patients (50.23), their QIRC score remained good (46.64±4.23) (ie, similar to contact lens wearers). Five of these nine patients were negative about their refractive surgery. Seven (6.7%) LASIK patients had a very low QIRC score (37.86±2.13), which included the five who volunteered negative comments and the two who did not comment. Three of these patients were still wearing spectacles all day every day and two of these patients were experiencing rapid increases in their myopia. Two patients suffered from significant dry eye, one of whom reported this prevented her from reading for any length of time and another was experiencing regular "eye infections" due to dry eye.

Table

TABLE 2A Comparison of Mean (±SD) Responses on Each QIRC Question by Type of Refractive Correction

TABLE 2

A Comparison of Mean (±SD) Responses on Each QIRC Question by Type of Refractive Correction

Table

TABLE 2A Comparison of Mean (±SD) Responses on Each QIRC Question by Type of Refractive Correction

TABLE 2

A Comparison of Mean (±SD) Responses on Each QIRC Question by Type of Refractive Correction

DISCUSSION

The Quality of Life Impact of Refractive Correction (QIRC) questionnaire was implemented on a sample that approximated the UK population demographics for refractive error correction in terms of age, gender, socioeconomic classification, and ethnicity. Although the groups were similar to population norms, the refractive surgery group was older than the spectacle and contact lens wearing groups. This is probably inevitable as it reflects UK population averages for uptake of refractive surgery in the pre-presbyope.33 Importantly, this shows that the population was representative of the overall UK population. Moreover, adjusting for age did not significantly diminish the significance of QIRC score differences between groups. The issue of age differences could be overcome with a longitudinal outcome study of refractive surgery. Indeed this has been performed,34 but this type of study raises selection bias issues as individuals self-selecting for refractive surgery maybe more troubled by spectacles or contact lenses than individuals who are happy to continue to wear them. It is important to perform both of these studies.

The principle finding of this study is that the QIRC questionnaire is effective at discriminating between individuals who wear spectacles, contact lenses, and those who have had refractive surgery. An important secondary finding is that post-refractive surgery patients have better quality of life than spectacle or contact lens wearing patients (see Fig 1). This finding is supported by previous outcome studies of refractive surgery, which have shown improved quality of life after laser refractive surgery.5,7"10,34,35 McDonnell et al5 suggested that patients with worse scores on visual functioning and well-being subscales might be more likely to seek refractive surgery correction. However, in this study, convenience seemed to be the key difference. Refractive surgery patients typically have little or no trouble using non-prescription sunglasses, seeing when waking, seeing when swimming or on the beach, or while exercising, and have the convenience of not thinking about spectacles or contact lenses before traveling, etc (Table 2). They also often believe that they look their best and have few concerns regarding the cost of their refractive correction. However, the usually high quality of life afforded by refractive surgery comes with a risk. Some common complications of laser refractive surgery such as loss of contrast vision, loss of best-corrected vision, regression, and dry eye problems were reported in our group.36 The QIRC effectively identified these patients, with the worse scores occurring for those patients who still required spectacle or contact lens correction or those with severe dry eye. The slightly higher than may be expected rate of individuals reporting poor outcomes may reflect the high sensitivity of the QIRC to these issues and the inclusion of hyperopic LASIK patients. Although we expect that our methodology resulted in a refractive surgery population typical of the UK refractive surgery population, it is likely that different results would occur with different procedures and in different settings.

Although the impact of surgery is most likely the cause of improvement in QIRC score, other factors should be considered such as cognitive dissonance.37 Cognitive dissonance states that a change in attitude or belief occurs in an attempt to be consistent with the choice taken. Patients who have chosen to undergo surgery could justify this choice by indicating that the outcome was successful. Dissonance increases as the degree of change increases. Although this probably plays a role, its impact is likely to be greater when asking about satisfaction or overall assessment of outcome as this directly targets justification issues, rather than when using a questionnaire where the way to distort measurement of outcome may not be as obvious. Nevertheless, cognitive dissonance may account for some of the differences between groups.

The majority of QIRC questions contributed to scoring differences between groups. The well-being questions were less discriminating by virtue of their high standard deviations. This indicates that individuals vary greatly in their response to these questions, although their fit to the Rasch model illustrates the importance of these items to the construct: refractive correction related quality of life.24

Pre-presbyopic contact lens wearers had a higher QIRC score on average than spectacle wearers. Typically, they were happier with their appearance than spectacle wearers, confirming a previous report by Day and Jutai.38 In addition, they had less difficulty driving in glare conditions, less trouble using non-prescription sunglasses, and less trouble seeing when exercising (Table 2). Spectacle wearers were shown to have a lower QIRC score than the other two refractive correction modes (Table 2). This was particularly true of those individuals who thought that their refractive correction was medium or high.

Compared to the risks of complications from refractive surgery, the risks from contact lens or spectacle wear are low. The annual incidence of a loss of vision to <6/18 from microbial keratitis, the main cause of visual morbidity in soft contact lens wearers, is 0.0019%.39 Similarly, cases of traumatic eye damage from spectacle lenses have been reported, but the protective value of ordinary spectacle lenses (the relative risk of penetrating eye injury in non- wear of spectacles has been estimated at 10.2 times higher than in spectacle wear) far outweighs their danger.40 The lower risk profile of spectacles and contact lenses may explain their popularity in the marketplace despite a better quality of life option (eg, refractive surgery) being available.

The QIRC questionnaire can effectively differentiate between spectacle wearers, contact lens wearers, and post-refractive surgery patients. It has also been shown to be responsive to the impact of refractive surgery34 and has excellent validity and reliability.24 These qualities, along with the truly linear scoring afforded by Rasch scaling, make the QIRC questionnaire an ideal instrument for measuring quality of life outcomes of all types of refractive surgery.

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TABLE 1

Demographic Characteristics of the Study Sample

Figure 1. Columns showing mean (error bars±SD) responses for the total QIRC score by mode of refractive correction. Refractive surgery was significantly better than contact lenses (P<.01) and spectacles (P<.001). Contact lenses were significantly better than spectacles (P<.05).

TABLE 2

A Comparison of Mean (±SD) Responses on Each QIRC Question by Type of Refractive Correction

TABLE 2

A Comparison of Mean (±SD) Responses on Each QIRC Question by Type of Refractive Correction

10.3928/1081-597X-20060101-07

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