Quality of life in age-related macular degeneration: a review of the literature

Measures of health status, functional status, visual function and well-being are not, in themselves, QoL measures. However, they are all concerned with aspects of life that may be important to QoL.

The value of questionnaire data collected depends on the psychometric properties of the measure. Psychometric properties that are regarded as important in a measure include [10]:

In addition to these psychometric properties, the burden placed upon respondents should be considered (length of questionnaire, complexity of language, relevance of the questions) and that on administrators [45]. Where questionnaires are designed in one language and translated into other languages, linguistic validation is required, including cultural adaptation where needed [46]. Forward and backward translations are necessary (preferably reviewed by the questionnaire author) to ensure that the translations have not introduced semantic discrepancies. Clinician review can be helpful and cognitive debriefing interviews with people who have MD are needed to ensure that the translated items and instructions are understood as intended. Psychometric evaluation of each language version is necessary, at least on first use, before analysing data from multiple languages as one dataset.

The method of administration is a further consideration that is particularly important in visually impaired populations. Self-completion (pen and paper) has been found to elicit poorer scores than interview administration in some questionnaires [47‐49] but not in others [33]. Where scores differ, using two implementation methods in one study may result in people with worse vision, and having interview administration, under-reporting impairment compared with people self-completing the measure. This would confound the results. Generally it is better to use only one administration method in any one study.

A limitation of condition-specific or vision-specific measures of health status, functional status and QoL, even when they are interpreted appropriately, is that the scores are not comparable across diverse medical specialties [50]. One use for outcome measures is to assess the relative cost-effectiveness of different treatments and to inform decisions concerning allocation of limited funds. Such a measure, that could be used across all medical conditions and allow direct comparison, would be an asset for health economists. One technique that is adopted increasingly to achieve such comparisons is utility assessment. Utility values (also called preference measures) are quantitative expressions of preference for given health states. A scale is used where utility values range from 0 to 1; 0 represents death and 1 represents perfect health. Techniques used for eliciting this value include time trade-off (TTO) and standard gamble (SG) (see below). The utility value obtained can be used in conjunction with an estimate of life expectancy to calculate Quality Adjusted Life Years (QALYs). QALYs are estimates of life expectancy in full health. One year of life in a health state rated as perfect health (utility value of 1) = 1 QALY. Two years of life in a health state with a utility value of 0.5 = 1 QALY. Using a figure for the cost of treatment, a cost per QALY can be calculated. Such costs can be calculated for any clinical intervention, and have been used by medical decision makers such as the National Institute for Health and Clinical Excellence (NICE) in the UK to make choices between treatments. Health economists argue that non-preference PROs correlate poorly with preference measures and so are not suitable for use in economic evaluation [51]. It could be argued that preference measures, although convenient for calculating QALYs, do not correlate well with non-preference based measures as they do not measure quality of life [52]. Evidence that this is the case will be reviewed below. First, methods of obtaining utility values will be considered.

A number of studies have looked at the impact of MD on psychological well-being. In an American cross-sectional study investigating 86 MD patients with a VA of 20/200 or worse in at least one eye [30] participants reported greater emotional distress (Profile of Mood States [POMS] [65]) than similar aged people without visual impairment. Scores were comparable with those of people with serious illnesses such as melanoma and HIV. Poorer functional status (QWB [66]) was associated with greater emotional distress. Longer duration of MD was associated with lower levels of emotional distress, probably due to adaptation to the condition. Lack of adaptation, particularly the personal experience of vision loss as opposed to its effect on relationships, was associated with depression in an American study of 144 MD patients [67].

A further US cross-sectional study of 151 patients with advanced MD (VA of 20/60 or worse in the better eye) [68] reported that the rate of depressive disorder (32.5%) (DSM IV [69]) was twice that found generally among elderly people living in the community. The strongest associations found were between depression (DSM IV [69]) and both vision-specific (NEI-VFQ [38], SIPv [32]) and general disability (SIP [31]). There was only a weak association between VA and depression. In cross-sectional studies there is a potential reciprocal relationship between visual disability and depression (disability leads to depression and depression influences disability) [70], but in a longitudinal study causal effects in such relationships can be established.

A prospective, longitudinal US study recruited MD patients with recent (6 weeks previously) loss of vision in their second eye [70]. At baseline 17 (33%) of 51 participants met the criteria for clinical depression (a higher rate than the 16% found in the community) of whom only one was receiving treatment for depression, suggesting low levels of pre-existing depression. This group had poorer VA, and greater visual disability (Functional Vision Screening Questionnaire [FVSQ] [71]) and general disability (Community Disability Scale [CDS] [72]) than the non-depressed group. Six months later 40 people were followed up (people who dropped out tended to be more depressed at baseline than the follow-up participants). In people depressed at baseline and still depressed at follow-up (N = 7), those whose depression worsened had a corresponding decline in general and visual function independently of any change in VA.

Visual impairment in the elderly has been shown to be a predictor of suicide [73].

Decline in visual function inevitably leads to difficulties in performing daily activities and also in pursuing leisure activities. In a US study of 51 MD patients [74], 36 reported that they had lost valued activities as a result of impaired vision, reading and driving being the most common. In this sample, the relationship between VA and depression was mediated by loss of valued activities. In a postal survey of 2000 members of the UK Macular Disease Society using the Macular Disease Society Questionnaire (MDSQ) (Mitchell J, PhD thesis, Royal Holloway, University of London 2003) [75], 832 of 1420 respondents reported a reduction in the number of hobbies pursued due to vision loss since the onset of MD. In the entire sample the mean number of hobbies reported before MD was 3.54 compared with 2.20 at the time of the survey. Reading, enjoyed by 59% before diagnosis, but by only 20% at the time of the survey, was the most curtailed hobby, and crafts and driving were also severely affected. Poorer Well-being (W-BQ12), Present QoL and MD-specific QoL (MacDQoL overview items) were all associated with loss of leisure activities after controlling for severity of MD (registration status). Data from the MacDQoL [42, 44] indicate that the domain of leisure activities is one of the most highly negatively impacted by MD.

Impaired efficiency in carrying out activities of daily life can compromise cherished independence [76]. In a study of 156 people with MD, independence was the most highly negatively impacted domain of the MacDQoL [42]. An Australian qualitative study [77] reported that losing the ability to drive is a major factor in loss of independence and, as well as having to rely on others for mobility, can lead to social isolation, in itself a factor in the progress of depression. This study also indicated that people resist asking for help for fear of becoming a burden and go to great lengths to remain independent.

Loss of independence in MD may be such that it is necessary to go into residential care. Visually impaired people are over-represented in care homes [78‐80] where it is associated with elevated levels of depression [81]. Chalifoux [82] asserted that people with MD may be pressured by their families into entering residential care for their own safety, but he recommended that they should be encouraged to remain in the community for as long as it is practically possible.

Visual impairment due to MD may lead to unplanned for expense. In this elderly population, many of whom have very limited resources, financial outlay related to vision impairment may lead to hardship. Nevertheless, a French study found that people with MD pay for help in the home [83] and that expenses increased with worse VA. British research indicates that people spend money on optical and other devices [84]. Tasks such as home maintenance and dressmaking may have to be paid for where, prior to MD, people were able to carry out the work themselves. Some forms of treatment, such as photodynamic therapy (PDT), are expensive and may have to be paid for personally if National Health Service or insurance schemes will not allow the treatment. Treatments for conditions resulting from MD, including depression and fractures due to falls, may also be expensive [85]. 'Finances' was one of the least impacted domains of the MacDQoL [42, 44] but even so there was a good deal of variability in the scores of both impact and importance on the finances domain, showing that, for some people, finances are important for QoL and are negatively impacted by MD.

There is a positive association between increasing age and poorer sleep quality [86]. Sleep disturbance is itself associated with depression and other somatic symptoms and causes a deterioration in quality of life [86]. In a study of 6,143 elderly Scandinavian people, Asplund found that poor sleep, difficulty falling asleep and frequent awakenings were all more common among visually impaired men and women than in those without visual impairment [86]. It is possible, therefore, that the sleep deprivation experienced by people with MD may contribute to elevated levels of depression.

Only one study was found that reported the relationship between life satisfaction and MD. A small Australian cross-sectional study reported that people with MD (N = 30) reported poorer life satisfaction (Life Satisfaction Index – well-being) [87] social support and greater stress due to daily hassles than a control group without MD of similar age [88].

Williams et al [30] compared people with one or both eyes affected by MD in the US and found that those who were legally blind in only one eye reported greater emotional distress than those with bilateral blindness. Anecdotal evidence of greater distress among people with some vision in one eye compared with those with no vision was reported in much earlier work [92]. In both articles, fear of losing vision in the second eye was suggested as the cause of the greater distress. In contrast, in the MDSQ survey (Mitchell, 2003) respondents with only one eye affected reported better psychological well-being (W-BQ12) than those with bilateral MD. A qualitative study of men and women with varying severity of MD [77] found that people with only one eye affected reported that MD did not affect their day to day living but they worried about the future and the possibility of second eye involvement.

Many people experience deterioration in their hearing as they get older. When this is accompanied by visual impairment there can be considerable impact on QoL. Three population studies investigating dual sensory impairment in the elderly [93‐95] reported that both vision and hearing impairment impacted negatively on FS, with visual impairment having the greater effect. These studies had only small numbers of participants in some of the impairment categories and relatively blunt measures of impairment were used but nevertheless they were able to report that dual sensory impairment had a greater impact than either visual or hearing impairment alone [93, 94]. A large, longitudinal population study of older women (N = 6112) [96] reported that vision impairment alone, but not hearing impairment alone was associated with both functional and cognitive decline and women with dual sensory impairment were at greatest risk of functional and cognitive decline. Another population study of elderly people [97] relied on self-report of both vision and hearing impairment and a number of symptoms of depression. In spite of these rather crude measures, it was found that all three sensory loss groups (vision, hearing and dual) were more likely to report depressive symptoms than those without impairment, with greatest risk in the dual impairment group.

In studies of elderly populations it is likely that many people will have other medical conditions in addition to MD. Williams et al [30] reported that 66 of 78 participants with MD had other medical conditions. When compared with those in the sample who had MD as their only medical problem, there was no difference between the two groups in emotional distress, difficulties with IADLs, self-reported general health and functional status (QWB). Only 18% rated another of their medical conditions as worse than MD – a point that health economists would do well to take note of. A large, multinational study (Canada, France, Germany, Spain, UK) [98] found that neovascular MD patients had significantly more co-morbid conditions than a control group (2.5 vs 2.2) and the MD patients were more likely to have had cancer (9% vs 4%) and stroke (4% vs 1%). Falls were twice as common in the MD group (17% vs 8%) [85]. Conditions associated with age such as arthritis and osteoporosis can, for people with MD, further compromise their dexterity and confidence in carrying out daily activities, their ability to get out and about or to enjoy leisure activities and the effect may well be to reduce their QoL.

MD can also be the cause of co-morbidity. Hip fracture is common in the frail elderly population and visually impaired people are over-represented in this group of patients [99‐101]. Dutton commented that a familiar experience for ophthalmologists is to send away a newly diagnosed woman with MD without follow-up or referral to other services because her VA does not warrant it only to have her return to the clinic some months later with a much reduced VA and a consequent fractured hip which has resulted in her being taken into residential care [102].

A commonly co-occurring eye condition for people with MD is cataract. The presence of MD has been implicated in poor visual outcome following cataract surgery and some evidence suggests that the treatment may even worsen the progress of MD [103]. Several studies, however, have indicated that cataract surgery leads to improved vision function for MD patients [103‐105].

There is evidence to indicate that visual impairment carries with it an increased risk of mortality. McCarty et al [106] reported that VA worse than 6/12 more than doubled the risk of mortality over a 5-year period. The increased risk may be due to incidents such as falls or car accidents [106]. People with visual impairment may also be more prone to accidents in the home such as fires or mishaps with electrical appliances.

Visual hallucinations, known as Charles Bonnet Syndrome, are common in people with visual impairment. In a survey of eye clinic patients with MD (N = 100), 13% reported experiencing formed visual hallucinations [107]. Only five of these had reported the hallucinations to their doctors. Of 86 consecutive patients at a retinal clinic (24% with MD), 13 (15%) said they experienced visual hallucinations [108]. Two of those participants had reported the hallucinations to a doctor. Two hundred and eighty two (20%) of the 1420 respondents to the MDSQ said they had experienced hallucinations at some time since diagnosis with MD [75]. Over 40% (122) of these had spoken to a health professional about the hallucinations of whom 59 (21% of those experiencing hallucinations) were given an explanation. Some explanations were inaccurate or unhelpful e.g. psychological (N = 1), brain confusion (N = 1), stress (N = 2), nothing to do with MD (N = 1). In a study of 100 patients treated with PDT for predominantly classic CNV, five (5%) described experiencing structured hallucinations following treatment [109].

These studies indicate that people may be reluctant to report hallucinations for fear of being diagnosed with dementia or otherwise considered 'crazy' [75, 108]. This concern alone may impact on QoL, severity of MD and hallucinations notwithstanding. Mitchell reported that hallucinations were associated with poorer psychological well-being (W-BQ12 [15]) after controlling for severity of MD (Mitchell, 2003). Scott reported that, even among people with relatively good VA, those experiencing hallucinations demonstrated higher levels of emotional distress (General Health Questionnaire [GHQ] [110]) and decreased function (SIP [31]) compared with those without hallucinations [108]. Health professionals need to be aware of the likelihood of hallucinations in MD and ask patients if they have experienced them. Reassurance about the benign nature of the phenomenon and its often limited duration would prevent much distress [111, 112]. Cohen et al [109] suggested that all patients who undergo PDT should be told beforehand that hallucinations are a possible side effect of treatment. Such pre-emptive education may be the best approach for all people diagnosed with MD [89].

Low vision services, including assessment of vision and of patients' needs, LVA provision and training have been shown to lead to improved visual function (VF-14, four subscales of NEI-VFQ) [23] and to lead to better visual function compared with a control group (LVQOL) [37]. Better psychological status (less depression and more self-confidence (Geriatric Depression Scale [GDS] [115]) at the time of rehabilitation has been shown to be associated with better outcome (reading speed and accuracy, critical print size) [116]. An interdisciplinary service including contributions from optometrists, ophthalmic nurses, social workers and rehabilitation officers resulted in improvements to visual function (VQOL [117]) and fewer problems in daily living (Manchester Low Vision Questionnaire [MLVQ] [118]) [119]. One study by Reeves et al compared standard low vision care with enhanced regimens but found that no benefit accrued from the additional help [120]. The enhanced programme involved further training in the use of LVAs and provision of alternative LVAs if necessary. It also incorporated advice on lighting and other features of the home environment during the course of a single home visit by a rehabilitation officer. The 'enhancement' may simply have been too little. For example, other work [121] indicated that standard low vision care followed by additional teaching sessions enabling extra tuition, correction of poor skills, additional practice with more difficult tasks and answering patients' questions over a 4 week period resulted in improvements in vision function (NEI-VFQ) and reading speed (Pepper VRST) compared with a group who had only standard care. Although there was no measurable improvement in VA, the experimental group reported improvements in self-rated eyesight. Whereas in the Reeves et al study [120] participants were given advice on lighting in the home, low vision centres in Sweden go further by upgrading lighting in the homes of patients (in kitchen, hall and bathroom) where necessary. A study to evaluate the benefits of improved lighting provision [122] indicated improvements in some ADL performance (mainly in kitchen and bathroom) with better lighting, although there was deterioration in other ADLs, possibly due to deterioration in vision during the study. As part of the study, half the participants were provided with optimum task and mood lighting in the living room (according to individual needs). The control group reported improvements in general health, self-confidence and loneliness (not from a published scale), but not to well-being (Psychological and General Well-being Index [123]) at 6 months after light adaptation. The intervention group showed significant improvements in the same items but also reported improved physical condition, appetite, social contacts, self-confidence, temper, depressed mood, vitality and well-being (not psychometrically evaluated measures). As the living room is a place associated with leisure, it may be that enhanced ability to enjoy valued leisure activities influenced perceptions of these constructs. This possibility chimes with evidence cited in section 3.1 that loss of valued activities is associated with increased depression. Other work suggested that increases in illuminance of task lighting leads to improvements in contrast sensitivity and near VA [124] and the authors suggested that provision of additional task illuminance should be part of low vision rehabilitation.

Training in eccentric viewing has been shown to improve reading speeds [125]. No PROs were used in this study, but other work reported here (e.g. [12], Mitchell, 2003) has indicated the impact of losing reading fluency due to MD and it is likely that there would be a positive impact on QoL for people trained in eccentric viewing or assisted by low vision aids to regain reading fluency.

Psychosocial interventions to assist adjustment to MD are not generally available in health-care settings [126] but a number of studies offer evidence for the benefits of such programmes. In Sweden a course of eight weekly 2-hour meetings for groups of 4–6 people with bilateral MD led by occupational therapists was evaluated initially by qualitative focus group methodology [90, 127]. Participants' endorsement of their increased knowledge of MD, the social support offered by the meetings and improved self-efficacy in performing activities of daily living was supported by long-term evaluation of the course (28 months later) using quantitative methods [128]. Activities of daily living were investigated in the areas of meal preparation, self-care, communication, cleaning, mobility, shopping and financial management. Compared with people who had experienced standard care, those taking part in the courses reported higher levels of perceived security in performing 15 of 28 daily activities investigated including items relating to meal preparation, cleaning, mobility, communication and financial management. Self-care and shopping-related items were unaffected. Within the experimental group, participants reported improvement in 14 of 28 items at the 28 month evaluation, including items relating to meals, communication, cleaning, mobility and financial management. The control group reported lower levels of security in 12 of the 28 activities investigated, including items relating to meals, communication, cleaning, mobility, shopping and financial management. These findings illustrate the importance of education and support in preventing a decline in perceived security in performing ADLs as well as enabling greater perceived security.

A self-management intervention consisting of 6 weekly 2-hour group sessions was developed in the USA [129]. It included presentations, lectures, problem-solving and skills training with guided practice using cognitive-behavioural principles. Compared with a waiting list control group, participants reported improvements in emotional distress (POMS) and self-efficacy (scale developed for the study) and their use of LVAs almost doubled. Self-reported functional capacity and symptoms (QWB) did not improve. In a larger study using this programme, participants with higher baseline levels of depression reported greater improvements (POMS) compared with less depressed people in the experimental group and with depressed people in the control group. The experimental group showed improvements in vision function (NEI-VFQ) compared with controls (especially those more depressed at baseline). Improved self-efficacy was associated with decreased depression. The effects of the intervention were sustained at 6-month follow-up [130] when depression was lower overall in the experimental group than in the control group.

A cognitive-behavioural-based programme developed in Germany incorporated modules relating to relaxation, awareness of the associations between thought, emotion and behaviour, maximising personal and external resources, exchange of personal experience and provision of information [126]. In this small pilot study, the course of 5 weekly 2-hour sessions resulted in the experimental group (N = 14) reporting improvements in negative affect and depression (Positive and Negative Affect Schedule [131], GDS [115]), performance of ADLs (Multilevel Assessment Instrument [132], modified), personal autonomy (developed for study) and active problem orientation (Freiburg Inventory on Coping with Illness [133]) compared with the control group (N = 8).

In Leicester, UK, in a programme of peer support, 6 weekly 1 1/2-hour discussion groups were led by 3–4 people with at least 5 years' experience of living with MD [134]. Participants received leaflets which acted as guidelines for each topic for discussion in the group. Participant course evaluation indicated that the leaflets had given them useful information and that the aims of the course (to provide information about MD, to provide friendship and support and to help adjustment to MD) had been met. This was a small pilot study with 2 groups of 6 participants each. The sessions were well attended. Data indicated that people who reported poorest well-being (W-BQ12 [15]) at the start of the course showed significantly more improvement in well-being following the intervention. Thus greatest benefit was experienced by those most in need. Ten of the 11 participants completing questionnaires at follow-up said they would be willing to help run similar groups in the future for others newly diagnosed with MD, providing further evidence that the programme of peer support was beneficial for them and, with their assistance as future course leaders, could be rolled out to others.

Evidence shows that rehabilitation offers benefits to functional status and a number of psychological outcomes. Nevertheless, the services offered are patchy. A survey of 588 blind and partially sighted older people (with eye conditions including MD) in the UK [135] reported poor levels of support and care, with only 53% of participants having had a home assessment, around half receiving help with household tasks and shopping and as few as 7% receiving meals on wheels. Many lived isolated lives, with 62% living alone and 11% receiving a visit from a trusted person less than once a month. It was estimated that 82% of those who lived alone were in poverty. Although all the people in the survey were eligible for registration as partially sighted or blind, only 58% knew of a local society for visually impaired people. There was a similar picture of inadequate provision of low vision aids and equipment to help with cooking and housework. In a survey in West Glamorgan of people registered blind or partially sighted [84], of 66 participants (39 with MD) only 80% had been visited by a social worker. Few possessed safety or mobility aids although all those who had them found them helpful. Kitchen aids, tactiles (e.g. raised buttons stuck on to oven controls to indicate temperature settings), and talking timepieces were also owned by only a minority. Distribution of aids was irregular with some owning several and others none at all. Many people were not aware of the financial benefits that might be available to them.

Clearly there are many improvements that could be made to rehabilitation services for people with MD. Although none of the rehabilitation studies reviewed here measured the effect of interventions on QoL, many reported improvements in outcomes that may contribute to QoL.