Vision and Quality of Life: The Development of a Utility Measure

Abstract

purpose. To identify the content for a vision and quality of life–related utility measure (Vision Quality of Life Index [VisQoL]) for the economic evaluation of eye care and rehabilitation programs.

methods. Focus groups of the visually impaired elicited key concepts. Based on these and previous research, 33 items were generated. These were administered to visually impaired adults (n = 70) and a representative sample of unimpaired adults (n = 86). The item bank was reduced through examination of item properties, exploratory factor (EFA), item response theory (IRT), and structural equation modeling (SEM) analyses. The resultant model was confirmed through administration to a second sample of participants.

results. Focus group themes included physical well-being, social well-being, independence, self-actualization, emotional well-being, and planning and organization. Poorly performing items were eliminated on basic psychometric properties, including failure to discriminate. Next, EFA loadings were used to select items. Twelve items survived. To minimize redundancy, IRT analysis and SEM reduced the VisQoL item pool to six items (Cronbach α = 0.88). To confirm this model, these items were then administered to an additional 218 participants; 35% with a vision impairment. A pooled SEM analysis showed the model to have very good fit properties (root mean square error of approximation [RMSEA] = 0.000). A preliminary test of the model against visual acuity showed a significant monotonic relationship.

conclusions. The short 6-item VisQoL has excellent psychometric properties as a simple summative instrument. It can be used in its present state as a condition-specific outcome measure for the evaluation of healthcare interventions for the visually impaired. The descriptive model is also suitable for generating utility values for the economic evaluation of vision-related programs and services.

Vision impairment has a significant impact on the length ¹ and quality of life (QoL). ² Previous research has shown that vision impairment is associated with an increased risk of falls, hip fractures, depression, social isolation, greater need for community services and greater risk of admission to nursing homes. ^{1 3 4 5 6 7} As the Australian population ages and the average lifespan lengthens, more people will be faced with the challenge of adapting to vision loss. This will result in an increase in the demand for eye-care and vision-related rehabilitation programs and services. The provision of these services is costly; the annual cost of the burden of vision impairment in Australia is estimated at $4.8 billion. ⁸ Hence, in a limited-resource environment, it is critical to evaluate the effectiveness of interventions. 

The global goal of eye-care and vision-related rehabilitation programs and services is to improve the QoL of visually impaired people. Therefore, to assess accurately the value of a service or program, the impact on QoL should be considered, as well as the consumption of limited healthcare resources. Cost–utility analysis enables this assessment because it expresses the value of outcomes (typically improvements) in a universal unit, the quality of life-adjusted year (QALY) and the cost of providing the services. It is a critical tool in evidence-based medicine, as it considers both the quality and the efficiency of healthcare delivery, expressed as the cost per QALY gained from a service or program. 

The long tradition in ophthalmology of using objective psychophysical measures has served the field well, but is no longer considered sufficient. For several years, there has been an increasing demand for the inclusion of subjective instruments to indicate gains in health-related quality of life (HRQoL) in such a way that these gains can be compared with gains in other health fields. When gains are comparable, rational decisions about the allocation of scarce healthcare resources can be made. 

HRQoL measures are designed to evaluate the impact that health has on QoL and the positive or negative impact of medical care. These are useful measures because they are not restricted to a particular area of health that facilitates comparisons across different conditions. A widely used generic HRQoL measure is the EuroQoL Health Questionnaire (EQ5D). ⁹  

However, generic HRQoL measures may lack the sensitivity of disease- or condition-specific measures. ^{10 11 12} For instance, generic measures may be less responsive to clinically relevant changes in vision. ¹³ In addition, there are possibly some QoL issues that are specific to vision loss and hence are not adequately represented in a generic measure. ¹² Several vision-related QoL measures have been developed such as the Visual Function (VF)-14 for measuring visual functioning in cataract patients. ¹⁴ Other vision-specific instruments include the VCM1 (vision-related quality of life questionnaire), ¹⁵ the National Eye Institute Visual Function Quotient (NEI-VFQ), ¹⁶ the Activities of Daily Vision Scale (ADVS), ¹⁷ and the Impact of Vision Impairment profile (IVI). ² For the reasons just outlined it is widely accepted that studies should include both a generic and vision-specific measure. One allows comparison across conditions, and the other provides greater sensitivity to changes in vision-related QoL. 

However, for economic evaluation, particularly cost–utility analysis, these measures are limited in their suitability, as they do not generate utility values. A utility value is an indirect measure of a person’s QoL based on the person’s preference for a particular health state. In other words, it quantifies the value of QoL associated with a particular health state. Generally, a weighted index of preference is determined on a scale from 0.00 (death) to 1.00 (perfect or very good health). When this value is known over time, it can be used to compute QALYs (i.e., QALYs = utility value × length of time gained). QALYs can be used in cost–utility analyses. 

There are two ways that utilities can be obtained directly from respondents: by using the time-tradeoff (TTO) or by standard gamble (SG). TTO requires people to imagine living a fixed number of years with a particular health condition, and then to indicate how many of those years of life they would be willing to trade to have perfect health. SG determines the level of risk people are willing to take for a treatment that would give them perfect health. Both these direct methods have been used to determine vision-related utility values. For instance, one study reported a mean utility value of 0.72 for people with age-related macular degeneration with a TTO and 0.81 using the SG. ¹⁸ Utility values were also obtained for people with diabetic retinopathy, ¹⁹ as well as those who were blind. ²⁰ However, these direct utility values were based on a single utility model. For instance, the patients with diabetic retinopathy were asked how many of their remaining years they would be willing to trade to have perfect vision for the rest of their lives. ¹⁹  

Given that the impact of vision on QoL is multifaceted, to get a more accurate reflection of the overall value of vision, a multiattribute utility (MAU) model would be preferable. This is the second way utilities can be obtained. In an MAU instrument, the different parts of life that may be affected by a health condition are separately assessed, and then they are combined into an index that is presented on a life–death scale where 0.00 represents a death-equivalent state and 1.00 a perfect HRQoL state. There are several generic health utility measures, such as the Assessment of Quality of Life instrument (AQOL), ²¹ the EQ5D, ⁹ and the Health Utilities Index III. ²² However, these generic utility measures may not be sufficiently sensitive to vision-related QoL; hence, their use in the evaluation of eye care and vision-related rehabilitation programs and services may be limited. A vision-specific utility measure would overcome this difficulty. 

Due to these limitations in existing MAU measures, there is currently no instrument suitable for generating utility values for the purposes of cost–utility analyses of vision-related programs and services. In this project, we sought to address this deficit by the development of a multiattribute vision-related utility measure, referred to as the Vision and Quality of Life Index (VisQoL). 

Methods

The first step in determining the content of the VisQoL was to discuss in focus groups the participatory ability of people with impaired vision and their perceptions of QoL. Focus group methodology is a well-established technique used to canvass the range of thoughts about a topic and is also a useful aid in the design of questionnaires that contain terminology that is appropriate and understandable to a target population. Participants were recruited from existing self-help groups at the Vision Australia Foundation, so that the sample was representative of the demographic profile of people with impaired vision. The moderator discussed the purpose of the study with each group before commencement. A semistructured approach was used to conduct the groups. Focus group topics were guided by our previously validated QoL questionnaire, Impact of Vision Impairment (IVI) ² ; however, flexibility allowed for exploration of any concepts raised by participants. 

The key questions asked during the focus groups probed the effect of vision on self-care, mobility in and out of the home, participation in work and leisure activities, interaction with other people, and sense of oneself. There was also a question on which area of life vision has had the greatest impact. The concept of TTO was also introduced in the discussions. Grounded theory techniques were used to analyze transcripts and observer notes from the discussions. They were examined to identify distinct statements made, which were then coded into appropriate categories. 

Using the results from the focus groups and from previous research, the second step in the development of the VisQoL was to create an item bank. The desired number of items for the final VisQoL scale was 6 to 10. A database of 33 items was developed—a ratio of approximately 4:1 with the desired scale size. 

The third step was to determine the suitability and validity of the items in the item bank for inclusion in VisQoL and to reduce the number of items from 33 to approximately 6 to 10. Participants in this second stage were chosen to represent two groups: (1) people who were visually impaired, defined as visual acuity (VA) <20/30 in the better eye, and (2) those deemed nonvisually impaired, defined as VA 20/20 or better in both eyes. All participants were 18 years of age or over. 

People with impaired vision were recruited from the Royal Victorian Eye and Ear Hospital (RVEEH). Eligible participants were given the option of completing the questionnaire in the waiting room or taking it home and returning it via the reply-paid envelopes provided. In addition, participants were able to seek assistance from the research team, a family member, or a friend, if necessary to complete the questionnaire. The availability of assistance was important, as some participants were unable to read the questionnaire due to vision impairment. People examined and found to have normal vision from a population-based study, the Vision Impairment Project (VIP) ¹ were sent an invitation letter, explanatory statement, the VisQoL item bank, and a consent form by mail. Participants who chose to participate were asked to return the completed questionnaire and signed consent form using the reply-paid envelope. 

To reduce the item bank to the final structure, basic psychometric properties were examined. In addition, exploratory factor (EFA), reliability, item response theory (IRT), and structural equation modeling (SEM) analyses were conducted. 

The fourth and final step in the development of VisQoL was to confirm the structural equation model obtained in the pilot study with a second sample group. This second group was recruited using the same methods as in the pilot study—that is, people with impaired vision were recruited from the RVEEH, and those with normal vision were recruited from the VIP study. SEM was used with this sample to confirm the construction sample model. Because there are known difficulties with SEM ADF (asymptotic distribution-free) models constructed in AMOS, ²³ which may have provided misleading fit estimates, we pooled the two samples for a final confirmatory analysis. 

Ethics approval for the study was granted by the Human Research and Ethics committee of the RVEEH. Informed, written consent was obtained from each participant. The research study adhered to the tenets of the Declaration of Helsinki. 

General data analyses were performed on computer (SPSS ver. 11.5; SPSS Chicago, IL), ²⁴ the structural equation modeling was performed with AMOS (ver. 4.0), ²⁵ and the item-response theory analyses with Conquest. ²⁶  

Results

Focus Groups

Three focus groups were conducted, each with eight or nine participants. The age range was from 34 to 90 years, and 19 of 26 participants were women. The onset of vision loss ranged between 6 months and 54 years previously, and was the duration range of vision rehabilitation. The most frequent cause of vision loss was age-related macular degeneration (AMD). Other causes of vision loss included glaucoma, Stevens-Johnson syndrome, macular dystrophy, albinism, diabetic retinopathy, Leber syndrome, and congenital cataracts. All participants in the first two groups except one had VA < 20/200. In the third group, participants had VA between 20/60 and 20/200. 

Common issues were identified from the focus groups that were specific to vision impairment. Across the three focus groups, both intrinsic and mediating factors were revealed to facilitate participation and perceived QoL (Table 1) . Intrinsic factors were defined as issues concerning the self, such as independence, social well-being, emotional well-being, physical well-being, and self-actualization. Mediating factors, such as planning, organization, and strategic development, were defined as facilitating QoL through participation but were not an internal process or state of well-being. 

Development of VisQoL Item Bank

Based on the findings from the focus groups and previous research, ² 33 items were developed as potential content for a vision-related scale. The purpose was to have broad representation of the six dimensions suggested from the results of the focus groups: physical well-being, independence, social well-being, emotional well-being, self-actualization, and planning and organization (Table 2) . 

Pilot Study

The item bank was administered to 156 participants; 70 adults with VA <20/30 in better eye, and 86 with VA ≥20/20 in both eyes (Table 3) . Of the 70 people with a vision impairment, 18% had glaucoma as the main eye condition, 48% had a retinal condition, and 34% a corneal condition. 

The basic psychometric properties of items were examined; those failing to meet predetermined criteria were eliminated. The criteria were >80% loading on one response category; mean score <20% from either scale endpoints; SD <0.50; and item failing to discriminate between the two groups of respondents. Six items were eliminated (items 1, 6, 18, 31, 32, and 33). The other 27 items were classified as meeting the criteria either fully or partly. The next step was to conduct separate exploratory factor analyses on each of the dimensions. Five of the six dimensions proved unidimensional (i.e., no item loaded significantly on a second factor). The exception was self-actualization, for which item 10 loaded significantly on a second factor (0.91); it was discarded. 

To reduce the item pool to approximately two representative items from each of the dimensions, iterative unconstrained factor analyses were conducted. In each case, the procedure was to delete the item with (1) the poorest psychometric properties, (2) the lowest factor loadings, and (3) the lowest pooled principal component analysis loading. At the end of the iterations, 13 items were retained in the item pool (Table 4) . 

Exploratory factor analysis and reliability analysis (Cronbach α) were conducted on the remaining 13 items. Results revealed that all items loaded on the one factor (Table 5) . The high Cronbach α of 0.96 suggested redundancy among the items. 

Although these analyses indicated excellent properties of the putative preliminary scale, they also suggested considerable redundancy. A desirable quality of the VisQoL model is parsimony, so that the number of items are limited, to avoid double-counting, but still represent the multifaceted impact that vision has on QoL. For further item reduction, IRT and SEM were used. 

IRT examines the item degree of difficulty among a homogenous set of items for which the assessment scale reflects respondents’ underlying traits. Considering the nature of the data in this study—that is, the ordinal Guttman response scales rather than dichotomous responses—we perforemd the IRT analysis by using a polytomous partial credit model. ²⁷  

Figure 1displays all 27 items that were not rejected on the basis of their psychometric properties (listed in Table 4 ). The items marked in bold are those 13 items that were retained after the EFA procedure listed in Table 5 . The unobserved construct (a respondent’s ability to endorse responses, derived from their vision-related QoL impairment experiences) and the item difficulty are mapped on Figure 1 . Positive logit values suggest that these are items on which it is easy for respondents to endorse losses, whereas negative logits suggest respondents find it difficult to endorse losses on those items. 

The problem of item similarity is evident in Figure 1 , as it reveals that, with the exception of items V28 and V11, the item difficulties all clustered around the same logit area, perhaps implying that item selection may have been an artifact of the correlation pattern underpinning the EFA solution. The interpretation of Figure 1is that most respondents selected the first category (i.e., no impairment due to loss of vision) on almost all items. When they endorsed the second and/or subsequent categories they did so on almost all the items equally. Thus, although items may discriminate internally they do not discriminate at different levels of ability, hence double-counting may occur. This model gives rise to a very sensitive measure where there are gross differences between respondents and scores are summed. This sensitivity, however, would not reflect small shifts between those with marginally different vision-related QoL impairment. Therefore, in selecting items for inclusion in the final model, the IRT analysis indicated the importance of selecting items from across the logit spectrum, even when this led to lower EFA and SEM statistics. 

To remove this redundancy, the 13 items listed in Table 4were examined using ADF SEM, as item responses were nonnormally distributed. The evidence from the EFA indicated that the model was unidimensional, therefore an iterative procedure was followed. The start model included all 13 items, with items progressively removed. The four criteria for improved fit were a significant reduction in the χ² − value, improvement in the comparative fit index (CFI; the accepted value was >0.90), and an improvement in the root mean square error of approximation (RMSEA; the accepted value was <0.05). 

After iteration, the final model consisted of six items representing the six dimensions (refer to the ^Appendix for final items). It consists of items 5, 7, 11, 25, 26, and 28. The SEM statistics for the model indicated excellent fit properties: χ² = 6.359, df = 8; CFI = 1.000, RMSEA = 0.000. The Cronbach α was 0.88. 

The VisQoL descriptive system items were examined using partial-credit IRT. The results are given in Table 6 . This shows a wide range of weighted T-fit values, perhaps reflecting the diverse nature of the items within the VisQoL (not surprising, since these were originally chosen to represent different aspects of life). The worst-fitting item was that measuring organizing activities. That all item-difficulty threshold estimates are positive reflects that, in the community sample, few persons endorsed item response levels other than the top level. 

Confirmation of the Model

The final step was to confirm the structure of the model with the data from a second construction sample. The item bank of 33 items was therefore administered to an additional 218 adults; 77 adults with VA < 20/30 in better eye, and 141 with VA 20/20 or better in both eyes (Table 7) . 

SEM was used to confirm the model obtained from the pilot study. The SEM statistics confirmed the model to have very good fit properties: χ² = 11.91, df = 9; CFI = 0.972 (>0.90), RMSEA = 0.039 (<0.05). 

As noted in the Methods section, however, there are known difficulties with AMOS ADF models in which the sample sizes are under ∼200 cases. ²³ It follows that the two separate SEM models reported earlier (for the pilot and confirmatory samples) may be unstable. For verification, therefore, SEM was repeated with the pooled sample. The results are given in Figure 2 , which shows excellent fit of the model to the data. 

Preliminary Evidence of VisQoL Sensitivity

VisQoL scores were computed, based on a simple additive model where the first response to each item was coded 0, the second response 1, and so on. The two questions with N/A responses were coded as missing data, and the values were imputed using horizontal mean imputation. This procedure gave scores in the range of 0 to 28, where a score of 0 indicated an awareness that vision actively enhanced QoL, scores in the range of 1 to 4 suggested vision made no or very little impact on QoL (i.e., it was largely taken for granted), and higher scores indicated progressively greater impact on QoL. Because of data skewing, which was expected, in that most of the sample were from the community, the data were square-root transformed before analysis. 

The obtained score range was 0 to 27. The mean for the community sample was 2.99 ± 2.44 (SD) compared with 9.99 ± 6.15 for the vision-impaired sample (ANOVA_{transformed data}, F = 236.35, df = 1372, P < 0.01). When examined by visual acuity, the results shown in Figure 3were obtained, showing a monotonic relationship between visual acuity and VisQoL scores. 

Discussion

Six items formed a descriptive system for an instrument, the VisQoL, measuring the impact of vision loss on quality of life. Although designed for weighting as a multiattribute vision-specific utility measure, the psychometric properties and summative scoring of the VisQoL are such that summative scores can be computed and the VisQoL used as a simple evaluation instrument for vision-related programs and services. 

The items were drawn from the broad areas of social, emotional, and physical well-being; independence; self-actualization; and planning and organization. These categories were identified in the focus groups and were consistent with those of other QoL measures. ^{9 21} They also fit within the World Health Organization (WHO) description of good health as being due to the effect of physical, emotional, and social factors. ²⁸ An additional category was identified as being part of the intrinsic nature of QoL, self-actualization. 

Two important features of this research were the use of patients’ views and the application of a mixture of classic and modern test theory. Regarding the use of focus groups to determine the underlying constructs to be measured, the steps we followed were consistent with those outlined by the WHO Quality of Life Group (WHOQOL Group) for QoL instrument construction. ^{28 29}  

Other than for the AQoL, ³⁰ there is little evidence that MAU instruments have incorporated the patient’s perspective. Generally, they have been designed around the concerns of health clinicians, researchers, and policy makers. Fully conscious of the work of the WHOQOL Group, we set out to incorporate views of people with vision impairment. None of the psychometric tests used in the construction of the VisQoL suggested any difficulties with this procedure. Because it is patients whose lives are affected by healthcare interventions and resource allocation decisions, the procedures we followed to include their perspective suggests strong ecological validity for the VisQoL. 

A second feature of this research project was the use of both classic and modern test theory practices to select items for inclusion in the VisQoL. As the results showed, classic approaches to item reduction enabled the removal of most items, but failed to discriminate adequately between items with similar properties. Essentially, the classic test construction methods resulted in a bank of items with equivalent characteristics, whereas the available tests were insufficient to eliminate double-counting. We suspect that this situation may be common, because it arises because of the very properties of the tests themselves which rely on correlations between items. The use of IRT and SEM enabled us to examine these issues in more detail and to select a very parsimonious group of representative items for inclusion. This ability of modern test construction procedures is one that has wide applicability elsewhere. That almost identical results were obtained with a second construction sample suggests the robustness of the procedures used in the construction of the VisQoL. We should point out, however, that classic test construction axioms regarding sampling and modern test construction techniques are not fully compatible, as shown in the IRT modeling of the descriptive system probability thresholds (see Table 6and Fig. 1 ). That the thresholds are all positive logits reflects the effect of including both the community and visually impaired samples. Although a mixture of classic and modern techniques have been used elsewhere, ^{31 32 33} as far as we are aware, this is the first time that this approach has been applied in the MAU instrument field. We believe that it could be useful in future instruments. 

The final six items all load on the one vision-related QoL factor, whereas the results of the SEM indicate that they are measuring different aspects of vision-related QoL. Hence, it is likely these items form a unidimensional parsimonious measure but without extensive double-counting within the descriptive system. This is important, as it allows for the further development of a multiattribute approach to the measurement of vision-related QOL without violating utility theory axioms. ³⁴ Therefore, these six items represent a measure of vision-related QoL that is highly suitable for further development into a vision-related utility instrument. 

Even so, as this article shows, the VisQoL has excellent psychometric properties as a simple summative instrument which can be used in its present state as a condition-specific outcome measure for the evaluation of healthcare interventions for the visually impaired. 

Appendix 1

Table A1.

 

Final VisQoL Items

Q1	Does my vision make it likely I will injure myself (i.e. when moving around the house, yard, neighborhood, or workplace)?
	□ It is most unlikely I will injure myself because of my vision.
	□ There is a small chance.
	□ There is a good chance.
	□ It is very likely.
	□ Almost certainly my vision will cause me to injure myself.
Q2	Does my vision make it difficult to cope with the demands in my life?
	My vision
	□ has no affect on my ability to cope with the demands in my life.
	□ does not make it difficult at all to cope with the demands in my life.
	□ makes it a little difficult to cope.
	□ makes it moderately difficult to cope.
	□ makes it very difficult to cope.
	□ makes me unable to cope at all.
Q3	Does my vision affect my ability to have friendships?
	My vision
	□ makes having friendships easier.
	□ has no effect on my friendships.
	□ makes friendships more difficult.
	□ makes friendships a lot more difficult.
	□ makes friendships extremely difficult.
	□ makes me unable to have friendships.
	□ Not applicable; I have no friendships.
Q4	Do I have difficulty organizing any assistance I may need?
	□ I have no difficulty organizing any assistance I may need.
	□ I have a little difficulty organizing assistance.
	□ I have moderate difficulty organizing assistance.
	□ I have a lot of difficulty organizing assistance.
	□ I am unable to organize assistance at all.
	□ Not applicable; I never need to organize assistance.
Q5	Does my vision make it difficult to fulfil the roles I would like to fulfil in life (e.g., family roles, work roles, community roles)?
	My vision
	□ has no effect on my ability to fulfill these roles.
	□ does not make it difficult to fulfill these roles.
	□ makes it a little difficult to fulfill these roles.
	□ makes it moderately difficult to fulfill these roles.
	□ makes it very difficult to fulfill these roles.
	□ means I am unable to fulfill these roles.
Q6	Does my vision affect my confidence to join in everyday activities?
	My vision
	□ makes me more confident to join in everyday activities.
	□ has no effect on my confidence to join in everyday activities.
	□ makes me feel a little less confident.
	□ makes me feel moderately less confident.
	□ makes me feel a lot less confident.
	□ makes me not confident at all.

 Supported by Australian Research Council, Vision Australia Foundation. This research at the Vision Cooperative Research Centre was partly supported by the Australian Federal Government through the Cooperative Research Centre Program.

 Submitted for publication November 29, 2004; revised May 13, 2005; accepted September 14, 2005.

 Disclosure: R. Misajon, None; G. Hawthorne, None; J. Richardson, None; J. Barton, None; S. Peacock, None; A. Iezzi, None; J. Keeffe, None

 The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.

 

Table 1.

 

Representative Statements Made by Focus Group Participants

Independence statements

“It’s being able to manage your own life.”

“I think what we’ve really got to be a bit more careful about is not getting to the stage where you let people do everything for you.”

“…I’m not a baby, I’m not an imbecile, I’m a fully grown adult, I just can’t see.”

“Not having to rely on other people to get where you need to go.”

“I miss the freedom of driving a car. I used to love to go and explore.”

Self-actualization statements

“I would not have had the experience if I hadn’t lost my vision; overall, my life is richer, I’m meeting more people….”

“I have achieved more than I could ever dream of doing with help, with all the help I’ve had, there’s a great sense of achievement in what I’ve done.”

“I have learnt…how to be assertive and if I need help I am not nervous to seek help.”

“…because I’ve made the effort and can do it, I think I’ve got the confidence to do it.”

“…in mixed groups where you would stand out as being different, the effect it has on me is to make me an educator.”

Social relationship statements

“It’s difficult to just pop over and visit someone and because you can’t reciprocate you lose friends; they just drift away”

“…people talk to my mum instead of me, like I am not even there.”

“The worst problem I have found is people being overprotective.”

“I withdrew from mixing with strangers.”

“I think relationships with family are much closer.”

Emotional well-being statements

“It got to one stage at home, I broke down in tears and started screaming…I felt a whole lot better after that.”

“Having confidence is a very big part of whether I feel at all happy.”

“I was very angry that I couldn’t see and do the things that I wanted to do.”

“I still feel a great sense of loss and sometimes I really grieve.”

“Frustrated because you can’t get and keep a proper job so you are financially disadvantaged.”

Physical well-being statements

“I had a big fall recently and broke a vertebrae in my back.”

“The side effects of drugs taken to preserve vision were worse than the vision loss.”

“The fact of not being able to see properly is very tiring because you have to concentrate whether you’re in the house and doubly so when you are outside the house.”

“It is not only difficult to cope with impaired vision, but other disabilities come.”

“I’d be happy to go along the way I am if I don’t face the prospect of getting worse.”

Planning, organization and strategic development statements

“You have to rely on other people to get where you need to go, so you have to organize that.”

“You always have to have money in your wallet for a taxi.”

“A routine is important, especially have things in certain places and other people not coming in and moving them from that spot.”

“If I went to an area I did not know, I had to plan before I went out.”

“It takes such a long time waiting for taxis or waiting for public transport.”

Table 2.

 

VisQoL Item Bank: 33 Items across Six Broad Dimensions

	VISQoL Item Bank for Vision Module	Dimensions
V1	Difficulty coping with any health problems because of vision	Physical
V2	Effort needed to do everyday tasks because of vision	Independence
V3	Vision affects physical/emotional intimacy	Social
V4	Vision restricts me from doing things on the spur of the moment	Planning
V5	Increased chance of injury because of vision	Physical
V6	Being treated better/worse by family/friends because of vision	Social
V7	Difficulty coping with demands of life because of vision	Independence
V8	Vision affects attitude toward life	Self-actualization
V9	Have ways to overcome problems due to vision	Planning
V10	Able to give help/advice to others because of experience with vision loss	Self-actualization
V11	Vision affects ability to have friendships	Social
V12	Frequency that I get upset about vision	Emotional
V13	Vision affects my awareness of what is happening around me	Physical
V14	Frequency that I worry about vision getting worse	Emotional
V15	Vision affects ability to make new friends	Social
V16	Difficulty providing care for others because of vision	Independence
V17	Support from others affected because of vision	Social
V18	Vision causing anxiety about health	Emotional
V19	Difficulty making/avoiding social contact because of vision	Social
V20	Difficulty exploring new places because of vision	Independence
V21	Confidence to achieve things because of past achievements	Self-actualization
V22	How happy I am	Emotional
V23	Concern about how others treat me because of vision loss	Social
V24	Vision prevents me from achieving things I want to achieve	Self-actualization
V25	Difficulty organizing assistance needed	Planning
V26	Difficulty fulfilling roles because of vision	Self-actualization
V27	Vision restricts me from doing things I would like to do	Physical
V28	Vision affects my confidence to join in activities	Emotional
V29	Difficult to plan/organise activities because of vision	Planning
V30	Difficult to take care of self because of vision	Independence
V31	Vision makes me fearful about ability to cope with future problems	Emotional
V32	Dis-/satisfaction with assistance given for vision	Independence
V33	Vision restricts opportunities to make lifestyle choices	Self-actualization

Table 3.

 

Demographics of Participants in Construction Study

	Vision Impaired (n = 70)	Normal Vision (n = 86)	Total (N = 156)
Mean age (y ± SD)	67.0 ± 16.4	61.8 ± 8.7	64.1 ± 13.0
Gender (%)
Male	41.4	47.7	44.9
Female	58.6	52.3	55.1
Visual acuity* (%)
20/20 or better	0.0	100.0	56.2
<20/20–20/40	35.8	0.0	15.7
<20/40–20/60	29.9	0.0	13.1
<20/60–20/200	25.4	0.0	11.1
Worse than 20/200	9.0	0.0	3.9

*  VA in better eye.

Table 4.

 

Item Outcome: Psychometric Criteria and Dimension Factor Loading

Item	Psychometric Criteria Met	Dimension Factor Loading	Item Retained
Physical
V5	Yes	0.88	Yes
V13	Yes	0.80
V27	Yes	0.91	Yes
Independence
V2	Yes	0.85
V7	Yes	0.87	Yes
V16	Yes	0.84
V20	Yes	0.89	Yes
V30	Yes	0.77
Social
V3	Yes	0.65
V11	Partly	0.82	Yes
V15	Yes	0.80
V17	Partly	−0.40
V19	Partly	0.84	Yes
V23	Partly	0.68
Planning
V4	Partly	0.87	Yes
V9	Yes	0.84	Yes
V25	Partly	0.70	Yes
V29	Partly	0.80
Self-Actualization
V8	Yes	0.80
V10	Yes	−0.32
V21	Yes	0.74
V24	Yes	0.89	Yes
V26	Yes	0.89	Yes
Emotional
V12	Yes	0.91	Yes
V14	Yes	0.84
V22	Yes	0.68
V28	Yes	0.89	Yes

Table 5.

 

Results of the Pooled Exploratory Factor Analysis and Reliability Analysis

Item	Item Content	Principal Factor Loading
V04	Vision: restrict spur of moment	0.89
V26	Vision: difficult to fulfill roles	0.89
V27	Vision: restrict doing things I want to do	0.88
V19	Vision: make/avoid social contact	0.87
V07	Vision: coping with life’s demands	0.87
V05	Vision: likely to injure myself	0.87
V24	Vision: prevent me achieving things	0.87
V20	Vision: difficult to explore new places	0.87
V28	Vision: confidence to join activities	0.86
V12	How often get upset about vision	0.85
V09	Overcome problems due to vision loss	0.79
V11	Vision: ability to have friendships	0.68
v25	Vision: organizing assistance	0.66
Eigenvalue		9.11
% variance explained		70.08
Cronbach α		0.96

Figure 1.

 

Partial-credit model of the VisQoL items accepted from Table 4 . Map of the latent distribution and response model parameter estimates (item*step level suppressed).

Table 6.

 

Partial-Credit IRT Analysis of the VisQoL

Variables	Item Difficulty	Weighted Fit Statistics
				MNSG	T
1. Likely to injure myself	2.76	0.80	−1.4
2. Coping with life demands	2.16	0.83	−1.3
3. Ability to have friendships	4.45	1.58	2.1
4. Organizing assistance	4.04	1.58	2.5
5. Difficult to fulfill roles	2.61	1.18	1.1
6. Confidence to join activities	1.51	1.16	0.9

 Separation reliability: 0.97, χ² = 1432.91, df = 6, P < 0.001.

Table 7.

 

Demographics for Participants in Confirmation Study Sample

	Vision Impaired (n = 77)	Normal Vision (n = 141)	Total (N = 218)
Mean age (y ± SD)	66.2 ± 13.7	64.0 ± 8.3	64.8 ± 10.5
Gender (%)
Male	50.6	46.8	48.0
Female	49.4	53.2	52.0
Visual acuity* (%)
20/20 or better	0.0	100.0	66.7
<20/20–20/40	27.1	0.0	9.0
<20/40–20/60	18.6	0.0	6.2
<20/60–20/200	38.6	0.0	12.9
Worse than 20/200	15.7	0.0	5.2

*  VA in better eye.

Figure 2.

 

SEM of the VisQoL, showing standardized regression weights and squared multiple correlations for the error terms.

Figure 3.

 

Sensitivity, means, and confidence intervals of the VisQoL by visual acuity group.