Validity of the Adaptation to Age-related Vision Loss Scale in an Australian Cataract Population

Purpose: The Adaptation to Age-related Vision Loss (AVL) scale was developed to measure the adjustment of older adults who are adapting to late-life vision loss. The purpose of this study was to assess whether the AVL scale satisfies the Rasch model in a cataract population. Methods: The 24-item AVL scale (18 negatively and 6 positively coded) was mailed to 436 cataract patients for self-administration whilst they were on the waiting list for cataract surgery at the Flinders Eye Centre, Adelaide, South Australia. Rasch analysis was performed to determine whether the items were measuring a single construct (unidimensionality) as examined with fit statistics and principal components analysis (PCA) of the residuals. The ability of the scale to distinguish between the levels of adaptation of the participants (person separation) was investigated, with a value ≥ 2.0 established as the minimum acceptable. Results: The AVL scale was unable to differentiate sufficiently between participants’ levels of adaptation, indicating poor person separation. One item did not fit the construct, causing misfit. Furthermore, the five positively worded items did not appear either to measure the same construct as other items, resulting in lack of unidimensionality evidenced by PCA. Following the deletion of these items, the AVL scale was one-dimensional but a single item continued to misfit, so it had to be deleted, resulting in an 18-item AVL scale. Even so, the discriminating abilities of the scale continued to be poor. Conclusions: The AVL scale is not an appropriate measure of adaptation to vision loss in a cataract population

The Impact of Visual Impairment on Functional Vision of Children in Rural South India: The Kariapatti Pediatric Eye Evaluation Project

PURPOSE. To determine the impact of visual impairment on functional vision of children in a rural population of south India. METHODS. A visual function questionnaire (LVP-VFQ) was administered to 1194 children aged 7 to 15 years identified through a systematic random sampling technique from 144 hamlets of Kariapatti in rural south India as part of a larger population-based project. Visual acuity estimations and clinical examinations for morbidity were performed in these 1194 children. A Rasch analysis was performed to validate the use of the instrument in this population. Bootstrap estimates (95% confidence intervals) of the regression coefficients were used to compare visual function scores between children with normal sight and children with uncorrected monocular and binocular visual impairment

Functional vision performance in Indian school-going children with visual impairment

Functional vision refers to the use of vision to perform day-day tasks and is assessed by the ability to perform these tasks. Assessment of functional vision is an integral component of the management of children with visual impairment. The results of the assessment help in designing appropriate educational and rehabilitation intervention strategies. The L V Prasad-Functional Vision Questionnaire (LVP-FVQ) is a reliable and valid tool for assessing self-reported functional vision performance (FVP) in children. Self-reports are obviously the child's perception of his or her ability to perform certain tasks but they may not reflect actual performance. Various studies of FVP in adults have used actual performance measures of everyday tasks, but very few studies, even in adults with visual impairment, have compared self-reports and performance measures and none have included identical tasks on the 2 methods of assessment. To date, no study has assessed FVP using performance measures of daily tasks in the paediatric population. Therefore, the aims of the current study were: (1) To develop performance measures of FVP and compare them with self-reports of FVP from the LVP-FVQ in a prospective cohort of Indian school-going children with visual impairment. (2) To investigate the effect of a psychological attribute, self-concept, on self-reports, performance measures and the relationships between the 2 measures. (3) To investigate the relationship between clinical measures of vision and FVP. Performance measures of FVP for children with visual impairment were developed for 17 day to day tasks for comparison with self-reports of the same tasks for the LVP-FVQ. The LVP-FVQ was verbally administered by the researcher to 178 Indian school-going children aged between 8 and 17 years with visual impairment. Similarly, the performance of each of the tasks by these children was measured by the researcher. The performance measures for most of these tasks were recorded on continuous scales and later categorized to match the ordinal ratings from the LVP-FVQ. The self-report and performance measure ratings for the 17 tasks were then converted into the same metric using a Rasch model allowing an accurate picture of whether and how these two measures of FVP compared with each other. Rasch analysis was used to estimate the person ability and item difficulty for FVP from the 2 methods of assessment. Self-reports showed stronger correlations with performance measures of FVP than were hypothesized. Similar to some studies in adults, binocular high-contrast visual acuity was found to be the single most significant predictor of a child's functional vision performance. Contrary to expectations, self-concept did not have a significant effect on the relationship between the 2 measures. A few reasons for the stronger than expected relationship between the 2 methods of assessment of FVP in children with visual impairment are suggested. Firstly, the use of identical tasks for self-reports and performance measures of FVP is likely to improve the relationship. Secondly, the LVP-FVQ was developed using focus groups of children with visual impairment, their parents, low vision specialists and rehabilitation professionals leading to good content validity. Since children were included in the development of the LVP-FVQ, the tasks were representative of a child's typical daily life. Thus, the performance measures were also suited to the day-day tasks of school-going children but were not tapping any social and psychological issues relating to visual impairment. Thirdly, the use of Rasch analysis which addresses many of the issues of unequal measurement and defines a hierarchy of items for self-reports and performance measures could have led to higher correlations in the present study. Finally, the high reliability and validity of self-reports and performance measures of FVP in the present study may have contributed to the higher than expected correlations. None of the demographic variables or self-concept affected the relationship between self-reports and performance measures of FVP, but self-concept had a weak significant association with self-reports. This result is unique to this study and warrants further investigation. Binocular high-contrast visual acuity alone, the most common visual function measured in ophthalmic clinics, explained between one-third and two-thirds of the variance in functional vision performance. This confirms the expected trend that with worse visual impairment, FVP is lower. The addition of the variable, self-concept, resulted in a very small increase in the variability explained for self-reported FVP. Similarly, the addition of other clinical measures of vision such as binocular low contrast visual acuity and colour vision resulted in a small increase in the variability explained for performance measures of FVP. The correlation between binocular high-contrast visual acuity and performance measures of FVP was statistically significantly higher than that between binocular high-contrast visual acuity and self-reports of FVP. There are a few possible reasons for this higher correlation. Firstly, performance measures are considered to be a more "objective" form of assessment, while self-reports are a child's perception of his or her ability and therefore lack a context, which may result in either over-estimation or under-estimation of actual ability. Furthermore, performance measures include dimensions such as the time taken to perform a task or other criteria specific to a task, while self-reports do not use such qualifiers. Secondly, the higher correlation may be the result of the visual complexity of some of the tasks. While self-concepts of children with visual impairment played a small but significant role in the self-reported FVP, studies in adults with visual impairment have suggested that other psychological factors such as mood, anxiety, motivation etc. are associated with an individual's perception of visual performance. Future studies are required to explore the possible role of these and other factors in FVP in Indian school-going children with visual impairment. This thesis makes a significant contribution to the field of paediatric low vision rehabilitation by providing performance measures of FVP and relating them to self-reports in children with visual impairment and their relationship with common measures of visual function. With self-reports, the child is reporting his or her perception of ability to complete a task, where performance measures examine the child's ability to complete a task by observing his or her performance. Thus, although the two methods are comparable, it is because of the different yields from each of these measures that they are not considered interchangeable. A combination of the 2 measures where practical would perhaps provide a richer depiction of the FVP of children with visual impairment. As developing countries such as India have limited resources allocated for eye care services where less than seven percent of the gross national product is spent on health care, self-reports can be utilized together with clinical measures of vision (mainly visual acuity) to assess the FVP in children with visual impairment in a community setting. However, both methods of assessment of FVP together with clinical measures of vision are essential if a comprehensive assessment of FVP is to be carried out in children with visual impairment. Information from these assessments can help clinicians better understand the functioning of children with visual impairment and incorporate them in the management of low vision in school-going children with visual impairment in India

Development and validation of a questionnaire for assessment of functional vision performance in low vision children

BACKGROUND: The goal was to develop a reliable and valid questionnaire (the L V Prasad-Functional Vision Questionnaire, LVP-FVQ) to assess self-reported functional vision problems in day-day activities of school-going visually impaired children. METHODS: Visually related activities of school-going children thought to be affected by any ocular disorder resulting in visual impairment were considered for the LVP-FVQ. A draft L VP-FVQ was developed from pilot work using focus group discussions and trials on a sample of 32 visually impaired children. The 20-item LVP-FVQ developed consisted of 19 items in 4 domains that related to day-day activities of school-going children. In addition, there was one question that asked children to rate their vision with respect to that of normally sighted friends. The 4 domains of the L VP-FVQ included: distance vision, near vision, colour vision and visual field. The 20-item L VP-FVQ was administered verbally to seventy-eight visually impaired Indian children aged 8-18 years with varying levels of vision loss from a range of ocular disorders. A subject's assessment of his/her ability to perform each task was scored on a 5-point Likert scale. Reliability testing included test-retest reliability (intraclass coefficient) and internal consistency reliability (Cronbach's alpha). Construct validation included consideration of the content validity, comparison with WHO categories of vision loss, and concurrent validity wherein the domain scores were compared with the clinical measures of vision. The last question that asked children to rate their vision with respect to that of normally sighted friends was also validated. RESULTS: The 20-item LVP-FVQ was reduced to 14 items through item reduction. The last item was retained in the 14-item LVP-FVQ. The LVP-FVQ was easy to administer because it had a short test time and scoring was straightforward. The test-retest reliability varied from 0.76 to 0.92 and internal consistency reliability varied from 0.29 to 0.76 for the 4 domains. However, internal consistency for all the 13 items of LVP-FVQ was high (0.84). A factor analysis with orthogonal varimax rotation of 13 items gave 4 factors: (i) visually demanding high contrast tasks, (ii) moderately visually difficult low contrast tasks, (iii) self-care and (iv) play activities, explaining the underlying dimensions to 66.2 percent. Of these, the first factor alone explained 35.1 percent of the variance in the LVP-FVQ score. The mean total LVP-FVQ scores were not significantly different for subjects with moderate low vision (visual acuity <6118-6/60 in the better eye) compared to those with severe vision loss ( <6/60-light perception), indicating that subjects in both these groups reported similar degrees of difficulty with their overall functional vision. However, multiple regression analysis revealed the best predictors of high contrast distance and near visual acuities were the responses to two items relating to copying from the blackboard and reading at arm's length. CONCLUSIONS: The LVP-FVQ showed promising results as a reliable, valid and easily administered questionnaire to assess problems with functional vision in visually impaired children. Further refinement of the L VP-FVQ with additional items relevant to children with specific ocular disorders may increase its usefulness

Survey of visual impairment in an Indian tertiary eye hospital

A retrospective survey of 4, 122 consecutive patient records was performed in a tertiary care eye hospital in Hyderabad, India. Data collected included age, gender, visual acuity after completion of treatment and diagnosis. 62.8&#x0025; of the patients were male. After completion of treatment, 10.8&#x0025; had low vision (best corrected visual acuity &#x0026;lt;6/18 to 3/60 in the better eye) and 2.6&#x0025; were blind (best correct visual acuity &#x0026;lt;3/60 in the better eye). Most cases of low vision were found in the 50 to 70 year age group (42.9&#x0025;). The most common visual acuity range after treatment amongst patients with vision loss was &#x0026;lt;6/18 to 6/60 (71&#x0025;). The 4 main causes of low vision were cataract (21.4&#x0025; of low vision group), glaucoma (14.0&#x0025;), diabetic retinopathy (13.0&#x0025;), and retinitis pigmentosa (10.7&#x0025;). The 4 main causes of blindness were glaucoma (16.3&#x0025; of blind group), diabetic retinopathy (13.2&#x0025;), corneal opacities (11.6&#x0025;) and retinitis pigmentosa (11.6&#x0025;). It is suggested that patients with low vision at the conclusion of treatment be referred to a vision rehabilitation centre. Referral should be made in cases with a best corrected visual acuity &#x0026;lt;6/18 to 3/60 or with visual field loss to within 15&#x00B0; of fixation. Patients aged under 50 years of age are expected to achieve maximal rehabilitation success. Motivation and vocational requirements should be assessed in older or more complex cases before referral. The data of this study show that about 10&#x0025; of patients seen at a tertiary care eye hospital in India could benefit from low vision rehabilitation

The Development of the LV Prasad-Functional Vision Questionnaire: A Measure of Functional Vision Performance of Visually Impaired Children

PURPOSE - To develop a reliable and valid questionnaire (the LV Prasad-Functional Vision Questionnaire, LVP-FVQ) to assess self-reported functional vision problems of visually impaired school children. METHODS - The LVP-FVQ consisting of 19 items was administered verbally to 78 visually impaired Indian school children aged 8 to 18 years. Responses for each item were rated on a 5-point scale. A Rasch analysis of the ordinal difficulty ratings was used to estimate interval measures of perceived visual ability for functional vision performance. RESULTS - Content validity of the LVP-FVQ was shown by the good separation index (3.75) and high reliability scores (0.93) for the item parameters. Construct validity was shown with good model fit statistics. Criterion validity of the LVP-FVQ was shown by good discrimination among subjects who answered "seeing much worse" versus "as well as"; "seeing much worse" versus "as well as/a little worse" and "seeing much worse" versus "a little worse," compared with their normal-sighted friends. The task that required the least visual ability was "walking alone in the corridor at school"; the task that required the most was "reading a textbook at arm’s length." The estimated person measures of visual ability were linear with logarithm of the minimum angle of resolution (logMAR) acuity and the binocular high contrast distance visual acuity accounted for 32.6% of the variability in the person measure. CONCLUSIONS - The LVP-FVQ is a reliable, valid, and simple questionnaire that can be used to measure functional vision in visually impaired children in developing countries such as India