Construct validation of the Amblyopia and Strabismus Questionnaire (A&SQ) by factor analysis

Patient reported outcomes for phosphomannomutase 2 congenital disorder of glycosylation (PMM2-CDG): listening to what matters for the patients and health professionals

Background

Congenital disorders of glycosylation (CDG) are a growing group of rare genetic disorders. The most common CDG is phosphomannomutase 2 (PMM2)-CDG which often has a severe clinical presentation and life-limiting consequences. There are no approved therapies for this condition. Also, there are no validated disease-specific quality of life (QoL) scales to assess the heterogeneous clinical burden of PMM2-CDG which presents a challenge for the assessment of the disease severity and the impact of a certain treatment on the course of the disease.

Aim and methods

This study aimed to identify the most impactful clinical signs and symptoms of PMM2-CDG, and specific patient and observer reported outcome measures (PROMs and ObsROMs, respectively) that can adequately measure such impact on patients’ QoL. The most burdensome signs and symptoms were identified through input from the CDG community using a survey targeting PMM2-CDG families and experts, followed by family interviews to understand the real burden of these symptoms in daily life. The list of signs and symptoms was then verified and refined by patient representatives and medical experts in the field. Finally, a literature search for PROMs and ObsROMs used in other rare or common diseases with similar signs and symptoms to those of PMM2-CDG was performed.

Results

Twenty-four signs/symptoms were identified as the most impactful throughout PMM2-CDG patients’ lifetime. We found 239 articles that included tools to measure those community-selected PMM2-CDG symptoms. Among them, we identified 80 QoL scales that address those signs and symptoms and, subsequently, their psychometric quality was analysed. These scales could be applied directly to the PMM2-CDG population or adapted to create the first PMM2-CDG-specific QoL questionnaire.

Conclusion

Identifying the impactful clinical manifestations of PMM2-CDG, along with the collection of PROMs/ObsROMs assessing QoL using a creative and community-centric methodology are the first step towards the development of a new, tailored, and specific PMM2-CDG QoL questionnaire. These findings can be used to fill a gap in PMM2-CDG clinical development. Importantly, this methodology is transferable to other CDG and rare diseases with multiple signs and symptoms.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02551-y.

Development of Pediatric Eye Questionnaires for Children With Eye Conditions

PURPOSE

To develop patient-derived Pediatric Eye Questionnaires (PedEyeQ) to separately assess eye-related quality of life (ER-QOL) and functional vision in children with eye conditions.

DESIGN

Questionnaire development study.

METHODS

A total of 444 children (0 to <18 years old), across 10 diagnostic categories, were enrolled at 2 sites. All parents (n = 444) and 277 children (5 to <18 years old) completed master questionnaires, developed from patient-derived concerns. Factor analysis was performed to identify unidimensional domains (eigenvalue >1.0) and Rasch analyses (differential item functioning, targeting, fit) to reduce items (separate analyses for subjects aged 0-4, 5-11, and 12-17 years and for each factor).

RESULTS

The Child 5- to 11-year-old PedEyeQ consisted of 4 unidimensional domains/questionnaires: functional vision, bothered by eyes/vision, social, frustration/worry (10 items each). The Child 12- to 17-year-old PedEyeQ consisted of the same 4 domains (total 39 items). The Proxy 0- to 4-year-old PedEyeQ consisted of 3 questionnaires/domains: functional vision, bothered by eyes/vision, social (total 29 items). The Proxy 5- to 11-year-old PedEyeQ consisted of 5 questionnaires/domains: functional vision, bothered by eyes/vision, social, frustration/worry, eye care (total 39 items), as did the Proxy 12- to 17-year-old PedEyeQ (total 42 items). The Parent PedEyeQ consisted of 4 questionnaires/domains: impact on parent/family, worry regarding child's eye condition, worry regarding child's self-perception and interactions, worry regarding child's visual function (total 35 items). Rasch look-up tables were created for scoring.

CONCLUSIONS

By following a rigorous approach, we have developed Pediatric Eye Questionnaires for separately assessing functional vision and ER-QOL domains in children of any age and with any eye condition.

Development of a conceptual model regarding quality of life in Chinese adult patients with strabismus: a mixed method

Background

Substantial challenges have been reported in China in terms of the large number of adult patients with strabismus and their poor quality of life. Quality of life is a cultural concept that varies according to personal feelings and perceptions, and it is influenced by physical, psychological and social factors. However, to date, there has been no mixed-method research of the quality of life of Chinese adult patients with strabismus, and no conceptual model has been reported. This study aimed to utilize mixed methods to explore the influence of strabismus on health-related quality of life in Chinese adult patients and to develop a conceptual model.

Methods

Thirty adult patients with strabismus from three tertiary hospitals in China participated in the interview. In-depth one-to-one interviews were semi-structured and addressed strabismus-related symptoms and the impacts on the participants’ quality of life. Transcripts were analysed to identify themes. A self-designed questionnaire was distributed to 448 patients, 437 of whom returned valid questionnaires. Descriptive statistics and x² test were conducted.

Results

Five themes were revealed regarding the impact of strabismus on patient quality of life: appearance, daily activities, personal development, social interaction, and emotions. In the survey, the top three symptoms (n ≥ 70%) rated by the participants were monocular vision, eye fatigue and physical discomfort. Compared to those without diplopia, the patients who suffered diplopia more often reported experiencing the symptoms of blurred vision, monocular vision, physical discomfort, eye fatigue, cannot estimate depth well and increasing deviation size (all p < 0.05).

Conclusions

This study is the first to examine quality of life among Chinese strabismus patients using both qualitative and quantitative methods and proposing a conceptual model. Symptom burden and appearance were the two original reasons for the decreased quality of life, and they were also the triggers for strabismus patients to visit clinics and undergo surgery. The interventions to treat symptoms burden should be different between patients with and without diplopia.

Differences in quality-of-life dimensions of Adult Strabismus Quality of Life and Amblyopia & Strabismus Questionnaires

Purpose

The Adult Strabismus Quality of Life Questionnaire (AS-20) and the Amblyopia & Strabismus Questionnaire (A&SQ) both measure health-related quality of life in strabismus patients. We evaluated to what extent these instruments cover similar domains by identifying the underlying quality-of-life factors of the combined questionnaires.

Methods

Participants were adults from a historic cohort with available orthoptic childhood data documenting strabismus and/or amblyopia. They had previously completed the A&SQ and were now asked to complete the AS-20. Factor analysis was performed on the correlation-matrix of the combined AS-20 and A&SQ data to identify common underlying factors. The identified factors were correlated with the clinical variables of angle of strabismus, degree of binocular vision, and visual acuity of the worse eye.

Results

One hundred ten patients completed both questionnaires (mean age, 44 years; range, 38–51 years). Six factors were found that together explained 78% of the total variance. The factor structure was dominated by the first four factors. One factor contained psychosocial and social-contact items, and another factor depth-perception items from both questionnaires. A third factor contained seven items—only from the AS-20—on eye strain, stress, and difficulties with reading and with concentrating. A fourth factor contained seven items—only from the A&SQ—on fear of losing the better eye and visual disorientation, specific for amblyopia. Current visual acuity of the worse eye correlated with depth-perception items and vision-related items, whereas current binocular vision correlated with psychosocial and social-contact items, in 93 patients.

Conclusions

Factor analysis suggests that the AS-20 and A&SQ measure a similar psychosocial quality-of-life domain. However, functional problems like avoidance of reading, difficulty in concentrating, eye stress, reading problems, inability to enjoy hobbies, and need for frequent breaks when reading are represented only in the AS-20. During the development of the A&SQ, asthenopia items were considered insufficiently specific for strabismus and were excluded a priori. The patients who generated the items for the AS-20 had, in majority, adulthood-onset strabismus and diplopia and were, hence, more likely to develop such complaints than our adult patients with childhood-onset strabismus and/or amblyopia.

Psychometric properties of the Chinese version of the Amblyopia and Strabismus Questionnaire (ASQE)

Background

Strabismus and amblyopia are known to cause visual dysfunction, self-image disorders, difficulty in seeking employment and social and emotional barriers. These factors can have a serious and detrimental effect upon the patients’ health-related quality of life (HRQOL). Presently, a condition-specific questionnaire is not available for assessing the HRQOL in Chinese patients. This study developed a Chinese version of the Amblyopia and Strabismus Questionnaire (ASQE) and tested its reliability and validity in Chinese adult strabismus patients.

Methods

Chinese strabismus adults, adults with normal vision and patients with a variety of other eye diseases completed the Chinese version of the ASQE. Reliability was established by Cronbach’s alpha and test-retest. Validity was evaluated by content, construct, criterion-related, convergent and discriminative validities.

Results

A total of 202 adult strabismus patients with or without amblyopia, 100 visually normal adults, and 100 patients with other eye diseases (excluding strabismus and amblyopia) participated in this study. Using principal components analysis, six domains were extracted, with a content validity of 0.91. Four items were deleted giving final total of 22 items in the questionnaire. The total score of the ASQE was significantly correlated to the Adult Strabismus Questionnaire (AS-20) (r = 0.642, P < 0.01). The median scores for the adult strabismus patients were significantly lower (worse HRQOL) compared with visually normal adults (66.32 vs. 92.71; P < 0.001) and patients with other eye diseases (66.32 vs. 79.50; P < 0.001) thus demonstrating good discriminative validity for the questionnaire. The Cronbach’s alpha coefficient for internal consistent reliability was 0.887 and the test-retest reliability was 0.946. The mean total score of the ASQE was 65.85 (SD = 15.32) and the domain ‘social contact and appearance’ recorded the lowest mean score 43.78 (SD = 13.92) in strabismus patients.

Conclusions

The revised 22-item Chinese version of the ASQE showed good psychometric properties. It is suggested that this questionnaire provides a potentially useful measurement tool in clinical or research programs involving Chinese strabismus patients with or without associated amblyopia.

Impact of strabismus surgery on health-related quality of life in adults

PURPOSE OF REVIEW

Adult strabismus can cause many symptoms, which have generally been divided into functional complaints and social complaints. The validity of surgical correction has historically been based on the restoration of functional improvement. In the absence of this expectation, surgery was labeled cosmetic. Yet, many studies have revealed the immense impact of ocular misalignment on psychosocial variables. The purpose of this article is to review the potential functional and psychosocial benefits of strabismus surgery and to summarize the development and status of questionnaires to help quantify these benefits.

RECENT FINDINGS

Functional benefits of strabismus surgery have been recently summarized with a meta-analysis. Several questionnaires have been evaluated to assess the functional and psychosocial factors in adult strabismus. Two strabismus-specific questionnaires, the Amblyopia and Strabismus Questionnaire and the Adult Strabismus-20, reveal improvements in adults following surgery. The appropriate patient population, impact of comorbidities on the scores, and the timing of the administration of the questionnaire postoperatively still need to be determined.

SUMMARY

Future studies of the impact of strabismus surgery in adults will need to report not only objective motor results, but also the impact on health-related quality of life to encompass all the benefits of strabismus surgery.

Health-related quality of life in children operated for pediatric cataracts

PURPOSE

To evaluate health-related quality of life (HRQOL) in children who had surgery for pediatric cataracts.

METHODS

Twenty-five children were divided into 2 groups according to the age at the time of survey (younger than 6 years in group A and 7 years and older in group B). A questionnaire that had 1 part appraising the child's perception and 3 parts evaluating the functional, social, and surgical apprehensions of parents was given to the participants. The questions in the first part were answered by parents in group A (proxy test) and by children in group B (self test). The correlations between the results and patient characteristics were evaluated statistically.

RESULTS

Mean (range) score for the first part was 79.5 (58-97) in group A and 70 (56-86) in group B. Functional, social, and surgical scores were 42.5 (0-80), 45 (5-100), and 63 (12.5-100) in group A and 40 (10-90), 70 (40-85), and 75 (25-100) in group B. Functional, social, or surgical scores were not significantly different between groups. Social apprehensions were significantly higher in parents of patients with preoperative strabismus in group B. Functional, social, surgical apprehensions, and children's thoughts were not correlated significantly with age, sex, family history, laterality, associated nystagmus, aphakia or pseudophakia, postoperative optical rehabilitation, or the need for additional surgery in the groups.

CONCLUSIONS

Although pediatric cataracts are known to have a great impact on children's life socially and functionally, there was no significant relationship between patient characteristics and HRQOL. The associated preoperative strabismus causes more social concern in the parents.

The impact of strabismus on quality of life in adults with and without diplopia: a systematic review

Strabismus affects approximately 4% of the adult population and can cause substantial physical disturbance and changes to appearance. This article aims to examine the impact of strabismus in adults both with and without diplopia, focusing primarily on quality of life (QoL). We highlight the value of measuring QoL, assess the ways in which it can be measured, and the impact the disease, diplopia, and surgery have on the patient. QoL differs for strabismus patients based on their diplopia status. Patients with diplopia tend to have more concerns relating to functional QoL, whereas patients without diplopia have primarily psychosocial concerns. Two diplopia-specific questionnaires have been designed to assess QoL and the perceived severity of symptoms. Further research is needed to identify the variables which influence QoL so that appropriate support can be given to all patients with strabismus to improve their QoL.

Does restoration of binocular vision make any difference in the quality of life in adult strabismus

BACKGROUND

To report the effect of restoration of binocular functions in adult strabismus on the health-related quality of life (HRQOL).

METHODS

61 adults undergoing strabismus surgery completed Adult Strabismus-20 (AS-20) and Amblyopia and Strabismus (A&SQ) HRQOL questionnaires preoperatively and postoperatively. Patients were grouped according to their responses to binocular tests as binocular vision positive (BVP) and binocular vision negative (BVN) groups. Changes in AS-20 and A&SQ scores of the overall group and the subgroups were evaluated.

RESULTS

Motor success was 90%, and 43% of the cohort showed measurable level stereopsis and central fusion on the Worth four-dot test or on the synoptophore. HRQOL scores (composite, psychosocial and functional) of the cohort measured by AS-20 and A&SQ showed significant improvement after surgery (AS-20: 42,40,45 vs 85,86,84, AS&Q: 46,52,38 vs 76,75,78, p<0.05 for all comparisons). But the BVP (n-26) group was not found superior to the BVN (n-35) group both functionally and psychosocially (p>0.05). Only after the exclusion of the amblyopic patients, functional superiority of the BVP group (n-20) over the BVN group (n-20) was disclosed (AS-20: 45 vs 31, A&SQ: 28 vs 16, p<0.05), while the composite and psychosocial subscale score improvements were not different (AS-20: 44,40 vs 34,38, A&SQ: 30,38 vs 20,37, p>0.05 for all comparisons).

CONCLUSIONS

The restoration of binocular vision is possible in adults with a long-term history of strabismus and both AS-20 and A&SQ questionnaires are sensitive to detect additive effect of binocular vision on functional aspects of the quality of life. To increase this sensitivity, questionnaires can be modified to include items inquiring tasks that require fine stereopsis.

Surgical and functional outcomes in bilateral exotropic Duane's retraction syndrome

AIMS

To evaluate the outcomes following surgery on patients with bilateral Duane's Retraction Syndrome (DRS) associated with exotropia or exophoria.

METHODS

Eleven consecutive patients with exotropic DRS were identified in a 10-year period. The case notes were reviewed, and data was analysed to evaluate the results following surgery. The preoperative and postoperative outcomes were evaluated for the angle of deviation in primary position, abnormal head posture, stereovision for near-fixation and horizontal ocular ductions.

RESULTS

All patients had a significant improvement in their angle of deviation in primary position, and 82% had a residual angle within 10 prism dioptres of orthotropia/phoria (p<0.001). For those patients with abnormal head posture, 86% resolved or improved. The postoperative cumulative horizontal ocular ductions measured less in nine patients by an average of 1.5 units. Pre-existing near-stereovision improved in 83% of the patients by an average of 40″ arc.

CONCLUSIONS

Surgery for bilateral exotropic DRS resulted in an improvement in the primary position angle and abnormal head posture. Patients demonstrated reduced cumulative horizontal ocular ductions restrictions and enhanced near-stereovision. This case series on exotropic bilateral DRS provides further evidence into successful postoperative surgical and functional outcomes.

Improved sensory status and quality-of-life measures in adult patients after strabismus surgery

PURPOSE

To evaluate the change in sensory status and quality-of-life measures in adults with long-standing childhood-onset constant strabismus.

METHODS

Consecutive patients with childhood-onset, long-term constant strabismus were enrolled. Sensory status was examined with Bagolini striated glasses test and Worth 4-dot test. Stereopsis was tested with the Lang and TNO stereopsis tests. Quality of life was studied with 2 different questionnaires (Short Form Health Survey [SF-36] and the Amblyopia and Strabismus Questionnaire [A&SQ]), which patients completed before and 3 months after strabismus surgery.

RESULTS

A total of 20 patients (age range, 18-63 years) were included, 10 of whom were esotropic and 10 of whom were exotropic. Of these, 13 obtained a satisfactory postoperative alignment and demonstrated an increase of sensory status with Bagolini striated glasses. Six patients who demonstrated suppression preoperatively achieved fusion and stereopsis postoperatively. The mean score in all domains of the A&SQ improved significantly, particularly with regard to social contact and cosmesis (P = 0.00067), distance estimation (P = 0.000312), and visual disorientation (P = 0.004777). Similarly, the mean score in 7 of 8 areas in the SF-36 improved significantly, particularly with regard to physical function (P = 0.000564), general health (P = 0.002296), vitality (P = 0.002891), social function (P = 0.004234), and mental health (P = 0.000334). The overall mean score of both questionnaires improved in all patients with a satisfactory postoperative alignment and increase of sensory status.

CONCLUSIONS

Surgical treatment of strabismus in adults with long-standing childhood-onset constant strabismus can result in patients feeling that their quality of life has improved and can restore binocular sensory function.

Amblyopia and quality of life: a systematic review

Amblyopia is a common condition, which can affect up to 5% of the general population. Health-related quality-of-life (HRQoL) implications of amblyopia and/or its treatment have been explored in the literature. A systematic literature search was undertaken during the period of 7-14 May 2010 to identify the HRQoL implications of amblyopia and/or its treatment. A total of 35 papers were included in the literature review. The HRQoL implications of amblyopia related specifically to amblyopia treatment, rather than to the condition itself. These included impact on family life, social interactions, difficulties in undertaking daily activities, as well as feelings and behaviour. The identified studies adopted a number of methodologies. The study populations included children with the condition, parents of children with amblyopia, and adults who had undertaken amblyopia treatment as a child. Some studies developed their own measures of HRQoL, and others determined HRQoL through proxy measures. The reported findings of the HRQoL implications are of importance when considering the management of cases of amblyopia. The issues identified in the literature review are discussed with respect to how HRQoL is measured (treatment compliance vs proxy measures), and whether HRQoL is taken from a child's or a parent's perspective. Changing societal views over glasses and occlusion therapy are also discussed. Further research is required to assess the immediate and long-term effects of amblyopia and/or its treatment on HRQoL using a more standardised approach.

Utility analysis of disability caused by amblyopia and/or strabismus in a population-based, historic cohort

Background

Amblyopia (prevalence 3.4%) is in principle treatable, but approximately one quarter of children do not reach reading acuity in the amblyopic eye. Adults with persistent amblyopia and/or strabismus experience a decrease in quality of life. This was now quantified by patient-perceived utility values.

Methods

Subjects were born 1962–1972 and had been treated by occlusion therapy for amblyopia by one orthoptist 30–35 years ago. All children in Waterland with amblyopia and/or strabismus had been referred to this orthoptist. Utilities were derived by methods of time trade-off, TTO (lifetime traded against perfect vision) and standard gamble, SG (death risk accepted for perfect vision). Most troubling eye disorder (low acuity of the amblyopic eye, lacking stereopsis or strabismus) was chosen and ranked among nine chronic disorders according to the subject’s perceived severity.

Results

From 201 patients that could be contacted 35 years after occlusion therapy — out of 471 who had been occluded — 135 were included: 17 could not be reached, 34 refused, and 15 had other reasons to not participate. Mean age was 40.86 years; 53% were male. Seventy percent were willing to trade lifetime according to the TTO method; its mean (log) utility was 0.963, i.e., a decrease in quality of life of 3.7%. Thirty-seven percent accepted death risk according to the SG method; its mean utility was 0.9996. TTO outcomes correlated with current near and distance visual acuity. Low acuity of the amblyopic eye, chosen as most troubling eye disorder, ranked slightly less severe than tooth decay.

Conclusion

Amblyopia and/or strabismus patients had a slightly decreased utility. The decrease is small but still important in the cost-effectiveness of vision screening because these conditions occur very frequently.

Health-related quality of life measures (HRQoL) in patients with amblyopia and strabismus: a systematic review

BACKGROUND/AIMS

Health-related quality of life (HRQoL) measures are used in healthcare to help inform clinical decision-making and policy-making decisions. A number of disease-specific or condition-specific measures have been developed and applied in ophthalmology; however, their use in the specific fields of amblyopia and strabismus are not as established. The purpose of this study is to identify and discuss specific HRQoL instruments that may be used in the investigation and management of patients with amblyopia and/or strabismus.

METHODS

A systematic literature review was undertaken in November 2009. The electronic databases of AMED (Allied and Complementary Medicine: 1985 to November 2009), the British Nursing Index and Archive (1985 to October 2009), Ovid Medline In-Process and Other Non-Indexed Citations and Ovid Medline (1950 to present) and PsycINFO (1806 to November Week 1 2009) were searched. No language restrictions were applied to the search.

RESULTS

Four instruments were identified: the Amblyopia and Strabismus Questionnaire (A&SQ), the Amblyopia Treatment Index (ATI), the Adult Strabismus Questionnaire (AS-20) and the Intermittent Exotropia Questionnaire (IXTQ).

CONCLUSION

The use of HRQoL measures in patients with amblyopia and/or strabismus is a developing area. Further research is necessary to determine the impact of issues such as diplopia and poor cosmesis upon patient groups, and to determine the influence of ethnicity and parental reporting in these patients.

Test-retest reliability of health-related quality-of-life questionnaires in adults with strabismus

PURPOSE

To report the test-retest variability of two health-related quality-of-life instruments: the new Adult Strabismus 20 (AS-20) and the National Eye Institute 25-item Visual Function Questionnaire (NEI VFQ-25), in adults with strabismus.

DESIGN

Prospective case series.

METHODS

Fifty-five adult patients in a clinical practice with stable strabismus completed the AS-20 and the NEI VFQ-25 at 2 visits, without intervening treatment. Questionnaires were completed the second time either at a subsequent office visit, immediately before surgery, or by mail. Intraclass correlation coefficients were calculated. Ninety-five percent limits of agreement and 95% confidence intervals around the 95% limits of agreement also were calculated.

RESULTS

There was excellent agreement of overall questionnaire scores for the AS-20 (intraclass correlation coefficient, 0.92) and NEI VFQ-25 (intraclass correlation coefficient, 0.94). The 95% limits of agreement for overall scores were 14.3 points (95% confidence interval, 10.9 to 17.7) for the AS-20 and 11.1 points (95% confidence interval, 8.5 to 13.8) for the NEI VFQ-25. The lower test-retest variability of the VFQ-25 seemed to be partly the result of ceiling effects with many scores at the normal end of the range.

CONCLUSIONS

The new AS-20 and the NEI VFQ-25 show excellent test-retest reliability in adults with strabismus. Change exceeding 95% limits of agreement (14 points on the AS-20 and 11 points on the VFQ-25) is indicative of real change in an individual patient. The AS-20 may be more useful than the VFQ-25 because it is less prone to ceiling effects in adults with strabismus.