Strabismus, 2014; 22(3): 100–110 ! Informa Healthcare USA, Inc. ISSN: 0927-3972 print / 1744-5132 online DOI: 10.3109/09273972.2014.932396

The Italian Version of the Amblyopia and Strabismus Questionnaire: Translation, Validation, and Reliability Giovanni Battista Marcon, 1

MD

1

and Raffaele Pittino,

MD

2

Strabismological Center, Bassano del Grappa, Italy and 2Casa di Cura Citta` di Udine, Udine, Italy

ABSTRACT Objective: To develop a culturally adapted Italian version of the Amblyopia and Strabismus Questionnaire (A&SQ) Health Survey and to test its acceptability, reliability, and validity in patients with strabismus. Study Design and Setting: The English A&SQ was translated into Italian after established cross-cultural adaptation procedures. The questionnaire was administered to 99 consecutive outpatients with strabismus and 39 normal adults and readministered after 2 weeks to 15 randomly selected patients and 26 adults with normal vision. Results: None of the participants had any problem in understanding the Italian A&SQ and 99% of the questionnaires were fully completed. The translated questionnaire has good discriminatory power between patients and healthy controls. Principal component analysis identified 7 factors, instead of the 6 in the original version. Cronbach’s alpha coefficient ranged from 0.64 to 0.77, and the test-retest reliability ranged from 0.92 to 1 and was adequate for all scales. Correlations with other disease activity parameters were generally as expected. Conclusion: The Italian A&SQ, with modified scales as principal component analysis suggest, appears to be an acceptable, reliable, and valid instrument for measuring health-related quality of life in Italian patients with strabismus. Keywords: Adult strabismus, public health/policy/standards, quality of life

INTRODUCTION

the investigation and management of patients with amblyopia and strabismus is the Amblyopia and Strabismus Questinnaire (A&SQ) developed by Van de Graaf et al.4 With the growing international collaboration in clinical research, the need for cross-culturally applicable instruments for outcome measures has also increased.5 One approach to meet this need is to translate and culturally adapt measures originally developed in English for use in a different cultural context. The aim of this study was to develop and evaluate a culturally adapted Italian version of A&SQ Health Survey for use in Italian-speaking people. The developed questionnaire was applied in Italian patients with and without strabismus to study its acceptability, reliability, and validity.

Measurements of health-related quality of life (HRQOL) are increasingly being used in clinical trials and health services research.1,2 HRQOL measures can be divided into generic and specific measures.3 Generic measures are not specific to any disease or population, and such measures can be used across various diseases. Specific instruments are specific to a disease, to a population of patients, to a certain function, or to a problem. When considering the application of HRQOL instruments within ophthalmology, there are concerns that generic measures are not sensitive to the recognized symptoms of vision loss or emotional aspects of a given ophthalmic condition, such as strabismus. Among the several specific measures, one instrument that may be used in

Received 17 February 2014; Revised 30 April 2014; Accepted 28 May 2014; Published online 8 July 2014 Correspondence: Giovanni Battista Marcon, MD, Via Bortolo Zonta 14, 36061 Bassano del Grappa (VI), Italy. Tel/Fax (Office) +390424511187. E-mail: [email protected]

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The Italian version of the Amblyopia and Strabismus Questionnaire

MATERIALS AND METHODS

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Psychometric Evaluation of the Italian A&SQ

Original A&SQ Questionnaire This instrument was designed based on an inventory of problems experienced by amblyopic and strabismic patients, gathered through patient interviews. These were categorized into 5 domains. The original A&SQ questionnaire4 contains 26 items, which are grouped into 5 multi-item scales measuring fear of losing better eye (FLBE), distance estimation (DE), visual disorientation (VD), diplopia (D), and social contact and appearance (SCA). The original A&SQ questionnaire was in Dutch. It was subsequently adapted to English by Felius et al.6

Translation and Cultural Adaptation of A&SQ Questionnaire We followed the proposed guidelines by Beaton et al.7 for translation and cross-cultural adaptation of HRQOL measures. Two forward translations of the US English A&SQ into Italian were done by two translators (one ophthalmologist and another by a Naive translator, both with Italian as their mother tongue). A synthetic version was developed by the translators. The synthesized version was backtranslated into English by a university teacher who worked in the United Kingdom for 6 years and a professional English translator. Both were masked to the US English version and naive to the concept measured. An expert committee that included health professionals (2 ophthalmologists, 2 pediatricians, a radiologist, a general medicine physician, and an epidemiologist) and the translators involved in the process reviewed all translations and verified the semantic, idiomatic, experiential, and conceptual equivalence between the source and the Italian version. Consensus was reached on any discrepancy, and a preliminary Italian version of the questionnaire was developed for field testing to check face and content validity.

Field Testing The preliminary Italian version of the A&SQ questionnaire was pretested in a convenience sample of 30 patients with strabismus enrolled in the private practice of the authors. After informed consent, the questionnaire was interviewer-administered to each subject and was probed on what he or she thought regarding what each item meant and the chosen response. Patients reported no problems answering the original questions, and therefore no further modifications to the instrument were made. !

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Patients and Data Collection A new sample of 138 patients—99 patients with strabismus and 39 adults with normal vision (without experience in the clinical management of strabismus)—were recruited consecutively in the private practice of the authors between January and December 2012 for the psychometric study. For the test-retest reliability, 41 patients were randomly selected. The study was performed following the principles of the Declaration of Helsinki. Informed verbal consent was obtained from all patients before enrollment. All participants were able to understand and cooperate with the study procedure. Patients having a history of coexisting major illness, psychological illness, or who were unwilling to provide verbal informed consent were excluded. All participants completed the A&SQ in an unsupervised manner in the waiting room. Visual acuity was measured (at 6 m) by a projector and optotypes. Unilateral visual acuity loss (presumably attributable to amblyopia in most cases) was categorized on a 4-point scale: level 1, interocular difference in visual acuity of 1 line (0.1 logMAR); level 2, interocular acuity difference of 2 to 4 lines; level 3, interocular acuity difference of 5 to 7 lines; and level 4, interocular acuity difference 8 lines. The levels of diplopia were assessed by the physician on a 4-point scales as follows: level 1, no diplopia; level 2, diplopia in sidegaze or upgaze; level 3, diplopia in primary gaze or downgaze; level 4, constant diplopia. The current angle of strabismus was measured by the alternating prism cover test during fixation at distance (6 m) and at near (30 cm). The angle of horizontal and vertical deviation at distance (prism diopters [PD] measured with alternating prism cover test) was assessed by the physician on a 3-point scales as follows. For horizontal deviation level 1, 10 PD; level 2 between 10 and 35 PD; level 3 35 PD. For vertical deviation level 1, 4 PD; level 2 between 4 and 14 PD; level 3 14 PD. Test-Retest Assessment A random sample of 41 patients (15 patients with strabismus and 26 visually normal adults) was interviewed twice using the A&SQ with an interval of 2 weeks. During those 2 weeks, no intervention was given. Scoring of the A&SQ All items are measured on Likert-type rating scales as in the original version of the questionnaire. For the purpose of scoring, the rating scales are assumed to be linear and run 0 to 100, where 0 corresponds to the least favorable score and 100 corresponds to the most favorable score. Intermediate response options are

102 G. B. Marcon and R. Pittino assigned a proportionate score.8 (It is thus assumed that the response options are positioned at equal distances on the scale—in other words, that the scale is a valid interval scale.) A 5-option item thus has possible scores of 0, 25, 50, 75, and 100, ranging from unfavorable to favorable. Scores on all items belonging to a subscale are averaged to arrive at the subscale score. The A&SQ total score is defined as the mean of all item scores. Statistical Analysis Psychometric evaluations were performed following the approach developed by the International Quality of Life Assessment (IQOLA) project.9 Descriptive statistics were used to examine the completeness of the data and to characterize the score distributions, including scale ranges, means, standard deviations, and floor and ceiling effects. The discriminant ability of the questionnaire was measured by comparison between patients and controls by the means of the Mann-Whitney test. Internal construct validity was assessed by principal component analysis with orthogonal rotation of the scales and by examining Pearson’s correlations between the scales. Six factors (fear of losing the better eye, far distance estimation, near distance estimation, visual disorientation, diplopia, social contact and cosmetic problems) have been shown to underlie the structure of the US English version of the A&SQ.10 Scaling assumptions were examined using the item discriminant validity approach, which is based on a comparison of the magnitude of the correlation of an item with its hypothesized scale as compared with other scales.9 The multi-item multitrait correlation matrix is used to compare the correlation of an item with its hypothesized scale to the correlation of the same item with all other scales in the matrix. Item discriminant validity is supported when an item correlates significantly higher (ie, two standard errors [SEs] or greater) with its own scale (corrected for overlap) than with the other scales. The default significance level for comparing two correlations is two standard errors. The standard error of a correlation coefficient is approximately equal to 1 divided by the square root of the sample size. The number of item discriminant validity tests for each scale equals the number of items in that scale, multiplied by the number of scales in the matrix minus one. Tests are summarized into 4 categories: (a) the correlation between an item and its hypothesized scale is significantly higher then the item-competing scale correlation (+2); (b) the itemhypothesized scale correlation is greater then the competing correlation, but not significantly so (+1); (c) the item-hypothesized scale correlation is lower than the competing correlation, but not significantly so (1); and (d) the correlation between an item and its hypothesized scale is significantly lower than the

correlation between the same item and another scale (2). Internal consistency was examined by Cronbach’s alpha coefficients and corrected itemscale correlations. Cronbach’s alpha coefficient measures the overall correlation between items within a scale and is considered acceptable at 40.70. Item-scale correlation assesses the extent to which an item is related to the remainder items of its scale and should exceed 0.40. Test-retest reliability of each scale was assessed by Pearson’s correlations between the scores from the 41 patients who were interviewed twice. As with Cronbach’s alpha, test-retest reliability coefficients 40.70 were considered adequate for group comparisons.9 Bland-Altman plots were used to analyze the variability of the differences in scores at first and second administrations. Besides the IQOLA approach for examining the internal validity and reliability, external construct validity was assessed by Spearman’s correlations between scores on the A&SQ scales and the clinical measures of disease activity: unilateral visual acuity loss, diplopia, and angle of horizontal and vertical strabismus. We expected that unilateral visual acuity loss correlated better with FLBE; diplopia with D, VD, and DE; angle of horizontal and vertical strabismus with SCA.

RESULTS Patient Characteristics A total of 138 consecutive Italian patients agreed to participate in the study. There were 85 (60%) female and 56 (40%) male patients with a mean age of 35 (range: 17–73) years. Ninety-nine patients (72%) had strabismus. The duration of strabismus varied between 6 months and 25 years. For the 99 strabismus patients (median age, 38 years; range, 17–73), diagnoses were cranial nerve IV palsy (n = 15), decompensated exotropia (n = 4), consecutive exotropia (n = 40), secondary exotropia (n = 7), Graves’ endocrine ophthalmopathy (n = 2), infantile esotropia (n = 7), partially accommodative esotropia (n = 6), decompensated esotropia (n = 3), esotropia in myopia (n = 8), cranial nerve VI palsy (n = 4), and cranial nerve III palsy (n = 2). Of the 99, 63 (63%) had diplopia and 36 (37%) did not. Visual acuity ranged from 20/15 to 20/50 (median, 20/20) for the better eye and 20/15 to 20/80 (median, 20/30) for the worse eye. For the 24 patients with a primary esodeviation, median angle of deviation by prism and alternating cover test (PACT) at distance was 30 PD (range, 10–80). For the 43 patients with a primary exodeviation, median PACT at distance was 35 PD (range, 18–80); for the 11 patients with a primary vertical deviation, median PACT at distance was Strabismus

The Italian version of the Amblyopia and Strabismus Questionnaire 14 PD (range, 3–35; the patient with 3 PD of vertical deviation also had significant excyclotorsion); and for the 21 patients with a vertical and horizontal deviation, median PACT at distance was 20 PD (range, 3–60) for horizontal deviation and 15 PD (range, 8–35) for vertical deviation. The 39 visually normal adults (median age, 33 years; range, 19–57) with no history of strabismus or amblyopia were orthotropic and had no more than 10 PD of horizontal and 1 PD of vertical heterophoria by PACT. For all normal subjects, stereoacuity was 40 seconds of arc using the TNO test, and bestcorrected visual acuity was at least 20/25 in each eye (median, 20/20 in each eye).

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indicates that all of the response choices are used. Table 1 also shows the prevalence of the ‘‘not relevant’’ responses, which were low except for two items: ‘‘ball games’’ and ‘‘parking car.’’ The main reason was that they had few social or physical activities. No patients minded answering any of the questions.

Response Distribution All values were observed for each item except item DE04 (Table 1). Patients showed restrictions on all scales (FLBE, DE, VD, D, SCA; Table 2). The items within the scale SCA were generally scored at lower levels.

Acceptability of the Final Italian Version of A&SQ Distribution of A&SQ Scores Patients did not have problems answering the original questions. Missing values for the individual items of the A&SQ were very low, ranging from 0% for most items to 1% for one of the SCA items (Table 1) and did not result in any missing values for the scale scores. The frequency distribution of individual items

Mean scales scores ranged from 37.9 (SCA) to 79.8 (DE) (Table 2). A full range of scores was observed in all the scales. The percentage of patients scoring at the lowest level was pronounced in the FLBE and SCA scales (29.6 and 29.1%, respectively). For the DE, VD,

TABLE 1. Item descriptive statistics (patients, N = 99). Item Name

Response value frequency Missing (%)

Mean

SD

100

75

50

25

0

Not relevant

Scale = FLBE (fear of losing better eye) FLBE01 See equally well both eyes FLBE02 Worry losing better eye FLBE03 Worry something gets into better eye

0.0 0.0 0.0

25.25 67.17 64.9

43.67 31.06 31.53

74 36 35

NA 18 13

NA 30 34

NA 8 10

25 7 7

NA

Scale = DE DE01 DE02 DE03 DE04 DE05 DE06 DE07 DE08 DE09 DE10

(distance estimation) Estimate distances well Good depth perception Put something on a table Miss other person’s hand when shaking hands Parking car Put cap on pen Put power plug into socket Pouring drinks Walk down stairs Play ball games

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

63.13 58.08 78.03 91.41 82.83 88.38 89.14 85.86 81.82 79.29

35.42 36.22 31.19 18.95 25.91 21.82 22.06 24.27 28.75 29.89

41 35 59 79 42 72 73 66 64 45

NA NA 12 9 15 13 16 18 12 14

43 45 14 8 15 10 5 10 13 15

NA NA 9 3 5 3 3 2 6 6

15 19 5 0 2 1 2 3 4 5

NA NA NA NA 20 NA NA NA NA 14

Scale = VD VD01 VD02 VD03

(visual disorientation) Find way in mall Find way in store Find way in train station

0.0 0.0 0.0

75.76 79.29 76.52

30.61 29.46 31.1

49 56 49

22 18 18

12 13 16

10 6 5

5 5 7

1 1 4

Scale = D (diplopia) D01 See double D02 Disturbing double vision D03 Reaching things when tired D04 Doing things when tired D05 Squinting one eye

0.0 0.0 0.0 0.0 0.0

61.11 66.92 80.05 71.21 54.04

38.5 36.57 28.12 30.17 33.45

41 23 58 44 22

9 7 16 14 18

18 18 15 26 26

15 16 7 12 20

16 10 3 3 13

NA 25 NA NA NA

Scale = SCA (social contact and appearance) SCA01 Eye contact one-on-one conversation SCA02 Eye contact group conversation SCA03 Misalignment SCA04 Feel insecure SCA05 Self confidence

0.0 0.0 1 0.0 0.0

47.22 50.51 26.02 39.39 26.26

33.67 32.53 28.47 34.09 33.57

18 20 6 13 9

12 11 3 9 5

28 32 20 19 10

23 23 29 31 25

18 13 40 25 48

NA NA NA 2 2

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NA

104 G. B. Marcon and R. Pittino TABLE 2. Descriptive statistics for scales (patients, N = 99). Raw scores Observed values

Scale Mean FLBE DE VD D SCA

52.44 79.8 77.2 66.7 37.9

SD

% at % at Lowest Highest Range floor* ceilingy

40.64 29.8 30.3 34.6 34

0 0 0 0 0

100 100 100 100 100

100 100 100 100 100

29.6 5.6 5.7 9.1 29.1

32.3 61.6 53.8 43 14.2

Raw score: Sum of item scores for the scale. *Percentage of respondents at the lowest possible scale score. yPercentage of respondents at the highest possible scale score. FLBE = fear of losing better eye; DE = distance estimation; VD = visual disorientation; D = diplopia; SCA = social contact and appearance.

TABLE 3. Comparison between controls (N = 39) and patients (N = 99) of the Italian A&SQ version. Scale

Controls Mean ± SD

Patients Mean ± SD

p

FLBE DE VD D SCA

100 ± 0 97.5 ± 4.3 93.8 ± 10.9 92.6 ± 8.3 94.6 ± 9.2

52.4 ± 40.6 79.8 ± 29.8 77.2 ± 30.3 66.7 ± 34.6 37.9 ± 34

50.001 50.001 50.001 50.001 50.001

high degree of grouping (Table 4). One hypothesized scale, SCA, had to be separated into two subscales: ‘‘social contact’’ (factor 6) and ‘‘appearance’’ (factor 5). Factor 1 matched to question relative to ‘‘object’s interaction,’’ factor 2 with ‘‘spatial interaction’’ and factor 7 with ‘‘diplopia.’’ Two items of the original hypothesized scale diplopia (D03 and D04) matched better to factor 2 (spatial interaction) and D03 to factor 6 (social contact). Two questions: ‘‘walk down stairs’’ (DE09) and ‘‘play ball games’’ (DE10) had a factor loading of50.50 on all factors, but did come close: 0.46 for DE09 and factor 1 and 0.49 for DE10 and factor 5. The correlations between the scales (Table 5) ranged from 0.13 (DE and FLBE) to 0.74 (D and VD). All the items (except the correlation between D and DE) were well below the preset 0,70 limits for distinctiveness of the concept being measured.

Tests of Scaling Assumptions

The control group of participants had better scale scores across all dimensions of vision-targeted healthrelated quality of life captured by the A&SQ (Table 3). All comparison between the control group and the patients were statistically significant (p50.001, Mann-Whitney test). Thus the translated questionnaire can be said to have good discriminatory power between patients and healthy controls.

Standard deviations of the items within the scales were generally comparable (Table 6). Corrected correlations between the items and their hypothesized scales ranged from 0.31 to 0.91 and were 0.4 or above for all items except for one item from the DE scale (DE10: play ball games). One item from the D scale (D03: reaching things when tired) correlated better with DE scale than its scale. Generally, items were significantly highly correlated with their hypothesized scale (ie, 42 Standard Error) than with the other scales. Exceptions to this were all items from the DE scale; item-scale correlation is higher for the hypothesized scale than for competing scales (D and VD), but not significantly. Likewise, for items D03 (reaching things when tired) and D04 (doing things when tired) from the D scale, the item-scale correlation is lower for the hypothesized scale than for competing scale (DE), but not significantly. Consequently, the scaling success rate on discriminant validity was 100% for all scales except DE and D (Table 7). Cronbach’s alpha ranged from 0.64 (D) to 0.77 (FLBE) and exceeded the 0.70 standard only for FLBE and SCA scales.

Internal Construct Validity

Test-Retest Reliability

Principal component analysis identified 7 underlying factors that together explained 74.7% of the total variance (Table 4). The responses to items in the original hypothesized scales are appropriately associated with the factors only for FLBE and VD (factors 4 and 3, respectively). Twenty-four of the 26 A&SQ items were mainly unidimensionally distributed along the 6 factors with eigenvalue 41.0. The nowfound structure was not completely congruent with the hypothesized domain structure, but still showed a

Test-retest reliability ranged from 0.92 to 1 (Table 7) and was adequate for all scales. Test-retest differences are plotted against mean scores, as described by Bland and Altman, in Figure 1.

Mann-Whitney test

and D scales, the percentage scoring at the highest level was also pronounced (61.6, 53.8, 43%, respectively).

Discriminant Ability

External Construct Validity Correlations between the subscales of A&SQ and the clinical parameters are shown in Table 8. Strabismus

The Italian version of the Amblyopia and Strabismus Questionnaire

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TABLE 4. Results of factor analysis (PCA and Varimax rotation) within the five A&SQ dimensions. Item

Seven-factor solution

Name

Label

Scale = FLBE FLBE01 FLBE02 FLBE03

1

(fear of losing better eye) See equally well both eyes Worry losing better eye Worry something gets into better eye

2

3

4

5

6

7

0.03 0.06 0.09

0.22 0.03 0.08

0.09 0.03 0.03

0.74 0.89 0.91

0.1 0.13 0.19

0.09 0.27 0.14

0.06 0.07 0.06

Scale = DE (distance estimation) DE01 Estimate distances well DE02 Good depth perception DE03 Put something on a table DE04 Miss other person’s hand when shaking hands DE05 Parking car DE06 Put cap on pen DE07 Put power plug into socket DE08 Pouring drinks DE09 Walk down stairs DE10 Play ball games

0.2 0.16 0.61 0.77 0.21 0.7 0.77 0.78 0.46 0.08

0.68 0.77 0.46 0.12 0.67 0.36 0.39 0.26 0.48 0.28

0.3 0.22 0.01 0.16 0.23 0.24 0.21 0.11 0.29 0.31

0.07 0.05 0.08 0.02 0.12 0.06 0.05 0.08 0.03 0.04

0.09 0.05 0.07 0.08 0.09 0.07 0.03 0.18 0.08 0.49

0.01 0.05 0.13 0.12 0.11 0.21 0.12 0.03 0.05 0.23

0.3 0.12 0.14 0.22 0.06 0.09 0.1 0.06 0.28 0.11

Scale = VD (visual disorientation) VD01 Find way in mall VD02 Find way in store VD03 Find way in train station

0.23 0.29 0.05

0.22 0.16 0.3

0.87 0.84 0.83

0.09 0.01 0.09

0.02 0.03 0.09

0.14 0.15 0.17

0.04 0.22 0.08

Scale = D (diplopia) D01 See double D02 Disturbing double vision D03 Reaching things when tired D04 Doing things when tired D05 Squinting one eye

0.25 0.22 0.57 0.31 0.05

0.19 0.25 0.62 0.64 0.42

0.08 0.2 0.01 0.13 0.01

0.09 0.09 0.06 0.19 0.09

0.06 0.02 0.1 0.18 0.11

0.12 0.05 0.17 0.09 0.61

0.86 0.85 0.2 0.31 0.33

Scale = SCA (social contact and appearance) SCA01 Eye contact one-on-one conversation SCA02 Eye contact group conversation SCA03 Misalignement SCA04 Feel insecure SCA05 Self confindence

0.07 0.12 0.12 0.24 0.17

0 0.01 0.08 0.07 0.03

0.2 0.23 0.01 0.06 0.03

0.09 0.15 0.01 0.11 0.14

0.27 0.2 0.69 0.78 0.84

0.82 0.84 0.19 0.29 0.15

0.02 0.06 0.05 0.13 0.02

Unrotated solution Eigenvalue % Variance explained % Cumulative variance explained

8.88 34.17 34.17

3 11.54 45.7

1.93 7.42 53.12

1.81 6.98 60.1

1.42 5.45 65.55

1.24 4.75 70.3

1.14 4.39 74.69

Rotated solution Eigenvalue % Variance explained

3.8 14.62

3.7 14.23

2.84 10.92

2.36 9.08

2.34 9

2.3 8.85

2.08 8

Factor loadings 40.50 are in bold. The table shows that the 7 non-rotated factors explained 34.2%, 11.5%, 7.4%, 7%, 5.5%, and 4.8%, together representing 70.3% of the item variance.

TABLE 5. Reliability coefficients and inter-scale correlations (patients; N = 99). Scale

FLBE

DE

VD

D

SCA

FLBE DE VD D SCA

(0.77) 0.13 0.15 0.27 0.37

(0.66) 0.56 0.74 0.3

(0.69) 0.45 0.31

(0.64) 0.37

(0.71)

Scale internal consistency reliability (Cronbach’s alpha coefficient) is presented in the diagonal. FLBE = fear of losing better eye; DE = distance estimation; VD = visual disorientation; D = diplopia; SCA = social contact and appearance.

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Correlations ranged from 0.12 (FLBE vs angle vertical strabismus) to 0.68 (D vs diplopia assessment). Among the correlations with the clinical parameters studied, the FLBE scale correlated best with the level of unilateral visual acuity loss (p50.01); the DE and D scales correlated best with the level of diplopia (p50.001 and 0.01, respectively); and the VD and SCA scales correlated best with the vertical strabismus angle (p50.001 and 0.01, respectively).

DISCUSSION An important consideration when using an HRQOL questionnaire is the cultural appropriateness of the measure. In this study, the standard US English A&SQ

106 G. B. Marcon and R. Pittino TABLE 6. Item descriptive statistics and Pearson item-scale correlations corrected for overlap (patients, N = 99). Item

Pearson item-scale correlations*

Name

Mean

SD

25.25 67.17 64.9

43.67 31.06 31.53

Scale = DE (distance estimation) DE01 Estimate distances well DE02 Good depth perception DE03 Put something on a table DE04 Miss other person’s hand when shaking hands DE05 Parking car DE06 Put cap on pen DE07 Put power plug into socket DE08 Pouring drinks DE09 Walk down stairs DE10 Play ball games

63.13 58.08 78.03 91.41 82.83 88.38 89.14 85.86 81.82 79.29

35.42 36.22 31.19 18.95 25.91 21.82 22.06 24.27 28.75 29.89

0.07 0 0.17 0.11 0.07 0.16 0.16 0.16 0.14 0.01

Scale = VD (visual disorientation) VD01 Find way in mall VD02 Find way in store VD03 Find way in train station

75.76 79.29 76.52

30.61 29.46 31.1

Scale = D (diplopia) D01 See double D02 Disturbing double vision D03 Reaching things when tired D04 Doing things when tired D05 Squinting one eye

61.11 66.92 80.05 71.21 54.04

Scale = SCA (social contact and appearance) SCA01 Eye contact one-on-one conversation SCA02 Eye contact group conversation SCA03 Misalignment SCA04 Feel insecure SCA05 Self confindence

47.22 50.51 26.02 39.39 26.26

Scale = FLBE FLBE01 FLBE02 FLBE03

Label (fear of losing better eye) See equally well both eyes Worry losing better eye Worry something gets into better eye

FLBE

DE

VD

D

SCA

NA 0.91* 0.91*

NA 0.13 0.13

NA 0.16 0.14

NA 0.28 0.24

NA 0.37 0.34

0.63* 0.55* 0.68* 0.49* 0.51* 0.73* 0.76* 0.69* 0.70* 0.31*

0.49 0.42 0.33 0.26 0.41 0.47 0.45 0.34 0.48 0.31

0.6 0.52 0.59 0.33 0.47 0.58 0.62 0.5 0.64 0.27

0.19 0.05 0.27 0.12 0.23 0.24 0.21 0.24 0.21 0.23

0.16 0.1 0.16

0.54 0.56 0.48

0.87* 0.87* 0.80*

0.39 0.47 0.41

0.27 0.29 0.32

38.5 36.57 28.12 30.17 33.45

NA 0.18 0.16 0.26 0.22

NA 0.53 0.8 0.7 0.31

NA 0.39 0.33 0.43 0.26

NA 0.55* 0.65* 0.7* 0.46*

NA 0.17 0.27 0.29 0.43

33.67 32.53 28.47 34.09 33.57

0.29 0.33 NA 0.27 0.28

0.19 0.25 NA 0.33 0.2

0.31 0.36 NA 0.24 0.09

0.26 0.37 NA 0.39 0.16

0.65* 0.64* NA 0.68* 0.55*

*Item-scale correlation corrected for overlap (relevant item removed from its scale for correlation).

TABLE 7. Test of scaling assumptions (Cronbach’s alpha, item internal consistency, item discriminant validity, and scaling success) (patients, N = 99) and test -retest reliability (n = 41). Correlations between items and scales Scale Fear of losing better eye Distance estimation Visual disorientation Diplopia Social contact & appearance

# Items

Cronbach’s alpha

Item internal consistency*

Item discriminant validityy

2 10 3 4 4

0.77 0.66 0.69 0.64 0.71

0.91 0.31–0.76 0.80–0.87 0.46–0.70 0.55–0.68

0.13–0.37 0.07–0.64 0.10–0.56 0.16–0.80 0.09–0.39

Scaling success Success/ Scaling Test-retest totalz success (%) (Pearson’s r) 8/8 25/40 12/12 9/14 16/16

100 62.5 100 64 100

1 0.92 1 1 1

p Values 50.05 for all correlation coefficients. *Range of correlations (Pearson’s) between items and hypothesized scales corrected for overlap. yRange of correlations (Pearson’s) between items and other scales. zNumber of significantly higher (42 standard errors) correlations between items and hypothesized scales/number of correlations.

was cross-culturally translated and adapted for use in the Italian culture in accordance with standard methodology.9 The findings showed that the Italian A&SQ appears to be an acceptable, reliable, and valid instrument for measuring HRQOL in Italian patients with strabismus.

As expected, the mean score in the patients group was much lower than controls. The floor and ceiling problems found are not specific to the Italian A&SQ, but are inherent to twoor three- point response format of some questions. In our study, factor analysis identified 7 factors, instead of the 6 of the English version. This fact may Strabismus

The Italian version of the Amblyopia and Strabismus Questionnaire be explained on the basis of the lack of robustness of the factor structure of the original instrument, different sample sizes of the studies, and the cultural and social differences between the Italian and English populations. This possibility of a cultural and social difference between the two populations would be worthy of more detailed study. Thus, according to the factor analysis, modifying the logical sequence of the Italian A&SQ may result in a more immediate and intuitive comprehension of the questions. As a result, new scales should be created as proposed in Table 9, leading to a patient-oriented approach. Two items, DE10 (‘‘play ball games’’) and DE09 (‘‘walk down stairs’’) had a factor loading of 50.50 on all factors. For the item DE10, the analysis suffers from the number of ‘‘not relevant’’ answers. However, the factor analysis identified an although weak correlation (0.49) with the scale ‘‘appearance,’’ probably due to the socializing aspect of this activity for the Italian population. These discrepancies may justify the elimination of the item. For the item DE09, from factor analysis resulted a weak correlation with two scales (see Table 4). Among those the most relevant were ‘‘object interaction’’ (0.46) and ‘‘spatial interaction’’ (0.48) scales. For these reasons, we thought to include the item DE09 in the scale with the higher factor

FIGURE 1. Bland-Altman plot of A&SQ.

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loading (‘‘spatial interaction’’). For the items D03 and D04, which were included in the ‘‘diplopia’’ scale in the original A&SQ version, factor loading was 40.50 on Factor 2 ‘‘object interaction’’ instead of Factor 7 ‘‘diplopia’’ by the factor analysis. Anyway, by the item-scale correlation (Table 6) these two questions correlated better to DE scale, which was split in two (‘‘object interaction’’ and ‘‘spatial interaction’’) by our factor analysis, than the original ‘‘diplopia’’ scale. The item D05 (‘‘squinting one eye’’) in factor analysis related better to the scale ‘‘social contact,’’ instead of diplopia. We believe the diplopia may be the underlying mechanism, but patients were probably more concerned by their appearance in our cultural context. The intuitive-deductive fashion (medical-oriented structure) of the original A&SQ questionnaire may be an explanation of this finding. In conclusion this item should be placed in the ‘‘social contact’’ scale in the final Italian version of A&SQ. All items passed the test of item internal consistency with the exception of one DE item (DE 10: play ball games). One item from the D scale (D03: reaching things when tired) correlated better with DE scale than its scale. We believe this result to be consistent in relation to our cultural and social context. The high correlation between scales measuring the same domain of health and the lower correlation between scales measuring separate domains of health confirmed the convergent and divergent validity of the scales. With the exception of items from DE and two for D, all items passed also the test for discriminant validity. This study also provided support for the reliability of the Italian A&SQ. The reliability of FLBE and SCA was above the 0.70 standard for group comparisons. For the other scales the Croanbach’s alpha was greater than 0.64, but did not reach the 0.70, as expected from factor analysis results. The test-retest reliability of the Italian A&SQ (ranging from 1 to 0.92) was adequate for all scales. Significant correlations were found between the A&SQ scales and the clinical parameters, in particular FLBE with the level of unilateral acuity loss, VD and

TABLE 8. Spearman correlation between scales and clinical parameters (patients)*. Scale Fear of losing better eye Distance estimation Visual disorientation Diplopia Social contact and appearance

Level of unilateral acuity loss (n = 99)

Diplopia assessment (n = 99)

Angle horizontal strabismus (n = 88)

Angle vertical strabismus (n = 30)

0.29b 0.07 0.07 0.09a 0.05

0.14a 0.53c 0.27b 0.68c 0.11a

0.11a 0.04 0.15a 0.07a 0.12a

0.12 0.29a 0.43b 0.26a 0.20a

*Listed is the Spearman rank correlation coefficient rs. Significant correlations are listed in bold (ap50.05, bp50.01, cp50.001). All significant associations have negative correlation coefficients because more favorable ASQE scores are higher, while more favorable disability scores and clinical parameters are lower. !

2014 Informa Healthcare USA, Inc.

108 G. B. Marcon and R. Pittino TABLE 9. A&SQ scales identified by factor analysis. Item

Seven-factor solution

Name Scale = FLBE FLBE01 FLBE02 FLBE03

Label (fear of losing better eye) See equally well both eyes Worry losing better eye Worry something get into better eye

1

2

3

4

5

6

7

0.03 0.06 0.09

0.22 0.03 0.08

0.09 0.03 0.03

0.74 0.89 0.91

0.1 0.13 0.19

0.09 0.27 0.14

0.06 0.07 0.06

Scale = OI (object’s interaction) OI01 Put something on a table OI02 Miss other person’s hand when shaking hands OI03 Put cap on a pen OI04 Put power plug into a socket OI05 Pouring drinks

0.61 0.77 0.7 0.77 0.78

0.46 0.12 0.36 0.39 0.26

0.01 0.16 0.24 0.21 0.11

0.08 0.02 0.06 0.05 0.08

0.07 0.08 0.07 0.03 0.18

0.13 0.12 0.21 0.12 0.03

0.14 0.22 0.09 0.1 0.06

Scale = SI (spatial interaction) SI01 Estimate distances well SI02 Good depth perception SI03 Parking car SI04 Walk down stairs SI05 Reaching things when tired SI06 Doing things when tired

0.2 0.16 0.21 0.46 0.57 0.31

0.68 0.77 0.67 0.48 0.62 0.64

0.3 0.22 0.23 0.29 0.01 0.13

0.07 0.05 0.12 0.03 0.06 0.19

0.09 0.05 0.09 0.08 0.1 0.18

0.01 0.05 0.11 0.05 0.17 0.09

0.3 0.12 0.06 0.28 0.2 0.31

Scale = VD (visual disorientation) VD01 Find way in mall VD02 Find way in store VD03 Find way in train station

0.23 0.29 0.05

0.22 0.16 0.3

0.87 0.84 0.83

0.09 0.01 0.09

0.02 0.03 0.09

0.14 0.15 0.17

0.04 0.22 0.08

Scale = D (diplopia) D01 See double D02 Disturbing double vision

0.25 0.22

0.19 0.25

0.08 0.2

0.09 0.09

0.06 0.02

0.12 0.05

0.86 0.85

Scale = SC (social contact) SC01 Squinting one eye SC02 Eye contact one-on-one conversation SC03 Eye contact group conversation

0.05 0.07 0.12

0.42 0 0.01

0.01 0.2 0.23

0.09 0.09 0.15

0.11 0.27 0.2

0.61 0.82 0.84

0.33 0.02 0.06

Scale = A (Appearance) A01 Misalignment A02 Feeling insecure A03 Self confindence

0.12 0.24 0.17

0.08 0.07 0.03

0.01 0.06 0.03

0.01 0.11 0.14

0.69 0.78 0.84

0.19 0.29 0.15

0.05 0.13 0.02

Unrotated solution Eigenvalue % Variance explained % Cumulative variance explained

8.88 34.17 34.17

3 11.54 45.7

1.93 7.42 53.12

1.81 6.98 60.1

1.42 5.45 65.55

1.24 4.75 70.3

1.14 4.39 74.69

Rotated solution Eigenvalue % Variance explained

3.8 14.62

3.7 14.23

2.84 10.92

2.36 9.08

2.34 9

2.3 8.85

2.08 8

Factor loadings 40.50 are in bold. The table shows that the 7 non-rotated factors explained 34.2%, 11.5%, 7.4%, 7%, 5.5%, and 4.8%, together representing 70.3% of the item variance.

SCA with the angle of vertical strabismus, and D with diplopia assessment, confirming the external construct validity of the Italian A&SQ. In summary, the Italian A&SQ appears to be an acceptable, reliable, and valid instrument for measuring HRQOL in Italian patients with strabismus and amblyopia. We believe our Italian version of A&SQ may well represent the quality of life perceived by our Italian amblyops and strabismic patients. The construct internal validity could be ameliorated with the new distribution of items in the new 7 scales identified. Prospective studies with the modified version of Italian A&SQ may confirm our hypothesis, and may lead to further elimination of items.

DECLARATION OF INTEREST I confirm that the manuscript has not been submitted elsewhere for national meeting. We have no conflict of interest or financial interests to disclose.

REFERENCES 1. Bowling A. Measuring Disease: a Review of Disease Specific Quality of Life Measurement Scales. 2nd ed. Buckingham, UK: Open University Press; 2001. 2. Fayers PM, Machin D. Quality of Life: the Assessment, Analysis and Interpretation of Patient-Reported Outcomes. 2nd ed. Chichester, UK: Wiley; 2007. Strabismus

The Italian version of the Amblyopia and Strabismus Questionnaire 3. Patrick DL, Deyo RA. Generic and disease-specific measures in assessing health status and quality of life. Med Care 1989;27:S217–S232. 4. Van de Graaf ES, van der Sterre GW, Polling JR, et al. Amblyopia & Strabismus Questionnaire: design and initial validation. Strabismus 2004;12:181–193. 5. Berzon R, Hays RD, Shumaker SA. International use, application and performance of healthrelated quality of life instruments. Qual Life Res 1993;2: 367–368. 6. Felius J, Beauchamp GR, Stager Sr DR, et al. The Amblyopia and Strabismus Questionnaire: English translation, validation, and subscales. Am J Ophthalmol 2007;143: 305–310.

7. Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine 2000;25:3186–3191. 8. Massof RW. A systems model for low vision rehabilitation. II. Measurement of vision disabilities. Optom Vis Sci 1998; 75:349–373. 9. Ware Jr JE, Gandek B. Methods for testing data quality, scaling assumptions, and reliability: the IQOLA Project approach. International Quality of Life Assessment. J Clin Epidemiol 1998;51:945–952. 10. Van de Graaf ES, Felius J, van Kempen-du Saar H, et al. Construct validation of the amblyopia and strabismus questionnaire (A&SQ) by factor analysis. Graefes Arch Clin Exp Ophthalmol 2009;247:1263–1268.

APPENDIX

APPENDIX The Amblyopia and Strabismus Questionnaire (A&SQ) (Italian version, March 2014). 1. Vedo egualmente bene con entrambi gli occhi Sı` 1 (vada alla Domanda 4) No 2 2. Sono preoccupato/a di perdere il mio occhio migliore Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 3. Sono preoccupato/a che qualcosa possa accadere al mio occhio migliore Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 4. Mi sento insicuro/a quando appoggio un oggetto su un tavolo Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 5. Nell’atto di stringere la mano, mi capita di non riuscire a farlo (di mancare la mano) Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 6. Ho difficolta` mettere il cappuccio ad una penna Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 7. Ho difficolta` a mettere la spina nella presa di corrente Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 8. Ho difficolta` a versare i liquidi nel bicchiere Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 9. Riesco a valutare bene le distanze Sı` 1 Abbastanza 2 No

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10. Ritengo di avere un buon senso della profondita` Sı` 1 Abbastanza 2 No 3 11. Ho difficolta` a parcheggiare l’automobile Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 Non rilevante perche´ non guido l’auto 12. Ho difficolta` a scendere le scale Mai 1 Raramente 2 Qualche volta

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3 Spesso 4 Sempre 5

13. Quando sono stanco/a mi capita di non riuscire ad afferrare degli oggetti, oppure di dover prestare molta attenzione per riuscire a farlo Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 14. Quando sono stanco/a mi capita di dover fare le cose piu` lentamente perche´ non vedo bene Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 15. Ho difficolta` ad orientarmi in un centro commerciale, specialmente se ci vado per la prima volta Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 Non rilevante perche´ non vado in questi posti 6 (continued ) !

2014 Informa Healthcare USA, Inc.

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110 G. B. Marcon and R. Pittino Appendix Continued

16. Ho difficolta` ad orientarmi in un supermercato, specie se mi trovo lı` per la prima volta Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 Non rilevante perche´ non mi sono mai trovato/a in questa situazione

6

17. Ho difficolta` ad orientarmi in una stazione dei treni, specialmente se ci vado per la prima volta Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 Non rilevante perche´ non frequento questi posti

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18. Vedo doppio Mai 1 Raramente

2 Qualche volta

3 Spesso 4 Sempre 5

19. Vedere doppio mi disturba nelle attivita` quotidiane (lavori domestici, studio, hobbies, attivita` lavorativa) Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 Non rilevante perche´ non vedo mai doppio

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20. Soffro di fotofobia (fastidio intenso e/o sensazione dolorosa in presenza di stimoli luminosi, ad esempio luce solare) Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 21. Ho difficolta` a mantenere il contatto visivo in una conversazione a tu per tu Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 22. Ho difficolta` nel mantenere il contatto visivo in una conversazione con piu` di una persona Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 23. I miei occhi sono mal allineati (uno o entrambi gli occhi incrociati, o ruotati all’esterno o in alto) Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 24. Mi sento insicuro/a a causa del fatto che i miei occhi sono mal allineati Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 Non rilevante perche´ i miei occhi sono allineati

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25. Se avessi gli occhi ben allineati, mi sentirei piu` sicuro/a di me Mai 1 Raramente 2 Qualche volta 3 Spesso 4 Sempre 5 Non rilevante perche´ i miei occhi sono allineati

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The Italian version of the Amblyopia and Strabismus Questionnaire: translation, validation, and reliability.

To develop a culturally adapted Italian version of the Amblyopia and Strabismus Questionnaire (A&SQ) Health Survey and to test its acceptability, reli...
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