A consistent increase in individuals with visual impairment is expected in the next few years, because of the increase in the elderly population worldwide (World Health Organization, 2004; Knauer and Pfeiffer, 2006).
According to Hinds et al. (2003), up to 90% of patients with low vision, however, have useful residual vision and may benefit from rehabilitative intervention; furthermore, assistive devices may help older individuals with visual impairments to slow the progression of decline, as individuals with visual impairment are at a high risk of developing disability (Dahlin-Ivanoff and Sonn, 2004).
The American National Eye Institute developed an instrument to measure vision-specific health-related quality of life, the National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25; Mangione et al., 1998), recognizing that the most meaningful outcome of a clinical intervention may be the patient’s own perception of changes in their well-being. In the shortened NEI VFQ-25, 25 questions have been created to survey patients with low vision deriving from a variety of eye diseases (Mangione et al., 2001). Several studies have shown an improvement in the NEI VFQ-25 scores after low-vision rehabilitation (Scott et al., 1999; Stelmack, 2001; Scilley et al., 2004), and have pointed out that modification of the questionnaire helps to improve its sensitivity for measuring the outcome of low-vision programs (Stelmack et al., 2002). As reading is one of the most important activities in the elderly (Elliott et al., 1997; Stelmack et al., 2008), we modified the German version of the NEI VFQ-25 (Franke, 2004) to test the impact of low-vision aids on patients’ quality of life focusing on reading ability. To control psychological comorbidity and bias, established outcome instruments were used, including the Hospital Anxiety and Depression Scale (HADS) (Zigmond and Snaith, 1983), the Mini-Mental State Examination Blind (MMSE-B; Busse et al., 2002), and two self-developed questionnaires quantifying patients’ expectation in respect of low-vision rehabilitation and life satisfaction.
Participants and data collection procedure
In this prospective interventional clinical study, consecutive patients scheduled for the Outpatient Low-Vision Service of the Department of Ophthalmology (Mainz) were asked to participate in the interview. After a minimum of 3 months after low-vision rehabilitation, patients were invited to the clinic for follow-up.
For each participant, occupation, marital status, and level of education were registered. General and ophthalmological medical history was determined.
Low-vision rehabilitation was carried out by experienced orthoptists and involved fitting magnifying devices and vision aids, together with careful instructions on their use. Suggestions for managing daily activities were also offered in the same visit, which took 60–120 min. A complete ophthalmological investigation was carried out.
Three months later, the interview and visual acuity (VA) assessment were repeated with the same interviewer if no eye operations had been performed in the meantime and the vision aids prescribed had been used for at least 4 weeks.
The NEI VFQ-25 (Mangione et al., 1998, 2001) consists of 25 items (39 in Franke’s German version; Franke, 2004) with 12 subscales: general health, general vision, distance tasks, near tasks, peripheral vision, color vision, dependency, role limitations, mental health, social functioning, driving, and ocular pain. The subscales driving, ocular pain, and peripheral vision were not used in this study, as they were considered irrelevant for our patient group for the following reasons: none of the patients attending our low-vision service fulfilled the legal visual requirements for driving; vision aids are usually prescribed when the eye disease is stable, not painful, and we wanted patients to concentrate on visual function and not to confuse it with discomfort. As we aimed to focus on reading ability, we excluded the subscale peripheral vision and we added the new subscale ‘reading ability’ (in the same format as the original NEI VFQ-25) consisting of two questions: (a) How would you estimate your reading ability with vision aids? (excellent, very good, good, moderate, bad); (b) How would you score your reading ability on a scale where zero is the worst and 10 is the best possible reading ability?
Our modified version of the NEI VFQ-25 (Modified German NEI VFQ-25) therefore had 35 questions with 10 subscales: general health, general vision, distance tasks, near tasks, color vision, dependency, role limitations, mental health, social functioning, and reading ability.
Answers to each question were converted into a 100-point scale, in which 100 represents the best possible score and zero the worst score, as suggested in the original versions.
Patients’ motivation was assessed by means of a self-developed questionnaire in which patients quantified their wish to achieve the following tasks with magnifying devices on a scale from zero (not important) to five (very important): 1, to be able to read again/better; 2, to watch television again/better; 3, to manage daily tasks better; 4, better mobility through improved orientation; and 5, other (to be specified). Life satisfaction was assessed by questions taken from the Indicators of the Rehabilitation Status questionnaire (Gerdes and Jäckel, 2005), inquiring about life satisfaction on a scale from 0 (very unsatisfied) to 7 (very satisfied) with respect to occupation, living situation, financial situation, leisure time, health, family, and general life satisfaction. Anxiety and depression were tested with the HADS, a reliable tool for screening psychological disorders (Zigmond and Snaith, 1983). The HADS comprises an anxiety (HADS-A) and a depression subscale (HADS-D). We used HADS-D of at least 8 for the detection of depression and HADS-A of at least 8 for the identification of clinically significant anxiety, as these cut-off points offer the optimal balance between sensitivity and specificity (Bjelland et al., 2002). Participants with cognitive impairments were excluded using the MMSE-B, where a score less than or equal to 17 was considered pathological (total score=22) (Busse et al., 2002).
The study was approved by the Institutional Ethics Committee and adhered to the Tenets of the Declaration of Helsinki. Each patient provided written consent to participate in the study.
Continuous variables were analyzed using a paired-samples t-test and Cohen’s d was calculated to identify effect size. Categorical variables were analyzed using χ2-tests. Linear regression and the Pearson correlation coefficient were used to explore the relationships between interview results and clinical and social characteristics. Statistical significance was set at P less than 0.005 for the main outcome (change of Modified German NEI VFQ-25 score after rehabilitation) and after Bonferroni’s correction for the 10 outcome measures. All other hypotheses were tested in an explorative manner; therefore, we report the exact P-values.
Because of the high dropout rate (42%) at follow-up, we used a multiple imputation procedure for missing data (Little and Rubin, 2002) by predictive mean matching using an expectation–maximization algorithm and Rubin rules (Rubin, 1987).
Between 8 June 2005 and 16 December 2006, 88 patients with visual impairment were enrolled in the study and attended the interview before receiving low-vision supports. In 50 (57%) cases, the interview was repeated on average 19.4±8.2 (SD) weeks later (participants). This was not possible in 37 (42%) cases for the following reasons (dropouts): no vision-aid prescription because of difficulty in managing, no visual improvement, etc. Twenty patients (23%), unable to make the second visit (10; 11%), had undergone ophthalmic surgery in the meantime (3; 3%), and four (5%) patients never collected the vision aids from the optical shop. One patient was excluded from statistical analyses because of a pathological MMSE-B score. The group of dropouts was analyzed for the baseline results separately from the study group, to identify distinctive characteristics.
Patients’ characteristics are shown in Table 1. Study patients (1.9±0.6) and dropouts (2.0±0.5) had a comparable number of eye diseases (Table 1).
Only 10 of 87 (12%) patients with low vision had never used vision aids before. A mean of 1.52±0.65 vision aids per patient was newly prescribed, most of them for near tasks. Telescopic devices for distance were prescribed only in six cases (12%).
Psychological and cognitive comorbidity
Interviews with HADS at baseline showed comparable anxiety and depression scores in the participants and the dropouts (anxiety score: 5.65±4.3 vs. 5.77±4.6; P=0.923; depression score: 6.20±3.2 vs. 5.72±4.5; P=0.568). With respect to HADS-D, 28% (n=14) of the participants scored in the range of clinically significant depression (HADS-D≥8), compared with 33% (n=12) of the drop-outs (overall 30%; n=26; P=0.595). Thirty-two percent (n=16) of the participants were in the range of clinically significant anxiety (HADS-A≥8), compared with 28% (n=10) of the dropout patients (overall 30%; n=26; P=0.674).
After low-vision rehabilitation, no significant changes were found for anxiety (5.3±3.7; P=0.186) and for depression (5.7±3.1; P=0.235).
The MMSE-B score was comparable in the two groups at baseline (study group 20.9±1.2 and drop-outs 20.8±1.1; P=0.622) and did not change after rehabilitation (20.8±1.2 vs. 21.0±1.3; P=0.385). One patient showed a pathological result (10) and was therefore excluded from further analyses.
Quality of life at baseline
No significant differences were found between the participants and the dropouts in the subscales of the Modified German NEI VFQ-25, except for the subscales general vision, color vision, and mental health, where dropouts showed better scores (Table 2).
Internal consistency (Cronbach’s α) for all subscales of the Modified German NEI VFQ-25 was good (0.77–0.85), including the short scales, in part consisting only of two items (Table 2).
VA in the better eye positively correlated with all Modified German NEI VFQ-25 subscales, and especially with the following subscales: general vision (r=0.495, P<0.01), near and distance tasks (r=0.476 and 0.430, respectively, P<0.01), social functioning (r=0.475, P<0.01), and dependency (r=0.435, P<0.01). Age and number or types of eye disease were not correlated to any subscale of the Modified German NEI VFQ-25. The number of systemic diseases was negatively correlated to the Modified German NEI VFQ-25 subscale general health (r=−0.503, P<0.01). Psychological comorbidity measured with HADS was negatively correlated with some of the Modified German NEI VFQ-25 subscales, and the stronger links were among depression and mental health (r=−0.475, P<0.001), dependency (r=−0.500, P<0.01), and role limitation (r=−0.423, P<0.01). Grade of life satisfaction was positively correlated to the Modified German NEI VFQ-25 subscale general health (r=0.466, P<0.01).
At the beginning of low-vision rehabilitation, improving reading ability was the most important goal, as this objective was marked as ‘very important’ by 62 of 69 patients (90%; Fig. 1).
Quality of life after low-vision rehabilitation
After low-vision rehabilitation, the Modified German NEI VFQ-25 showed better scores for the subscales of reading ability (P<0.001), near tasks (P<0.01), and social functioning (P<0.01; Fig. 2).
The magnitude of the change was moderate for near tasks and social functioning (Cohen’s d=0.44) as well as for reading ability (Cohen’s d=0.59). The improvement in perceived social functioning correlated with the change in the subscales near and distance tasks (r=0.404, P<0.01, and r=0.485, P<0.01, respectively), as well as with mental health and dependency (r=0.518, P<0.01, and r=0.420, P<0.01, respectively) but not with that of reading ability (r=0.149). There was no significant correlation between VA and change in the Modified German NEI VFQ-25 scores, except for the subscale dependency (r=−0.313, P<0.05). No significant correlation was found among the type or the number of vision aids prescribed and change in the Modified German NEI VFQ-25.
The improvement in self-estimated reading ability with vision aids was similar in the different subgroups analyzed. In linear regression models, with the Modified German NEI VFQ-25 posttest subscale scores in each case as a dependent variable and the pretest subscale scores as well as sex, education, familial situation, and primary eye diagnosis as independent variables, we found no significant predictor, except for pretest subscale scores.
Overall life satisfaction was similar at baseline for the study patients and the dropouts (5.06±0.8 vs. 5.33±1.0; P=0.158), and did not change after low-vision rehabilitation (5.17±0.9 vs. 5.18±1.0; P=0.946).
In this study, we examined the vision-specific health-related quality of life and the psychological state in a group of patients with low vision before and after rehabilitation. According to the literature (Varma et al., 2006; Evans et al., 2007; Langelaan et al., 2007), our group of patients with visual impairment showed not only low scores of vision-related quality of life and life satisfaction but also a higher prevalence of anxiety and depression than that reported for the general elderly population (Flint, 2005; Koster et al., 2010; Wolitz-Taylor et al., 2010). As already reported (Hazel et al., 2000), VA in the better eye correlated positively with all Modified German NEI VFQ-25 subscales. Depression was related to worse vision-related quality of life, as already reported (Owsley and McGwin, 2004), whereas age and number of ophthalmological diseases were not and systemic diseases were only weakly related, which is in contrast to other findings (Langelaan et al., 2009), where age was an important predictor for the change in quality of life. Among patients with visual impairment, the main ophthalmological diagnosis did not relate to the baseline NEI VFQ-25 scores, confirming that the questionnaire is appropriate for various eye diseases (Mangione et al., 1998, 2001) and that the level of VA rather than the specific disease is related to utility values in permanent visual loss (Stelmack, 2001). Both for age-related macular degeneration and for diabetic retinopathy, a correlation between a decrease in VA and an increase in the use of helping devices has been reported (Schmier et al., 2006, 2009).
We modified the NEI VFQ-25 to better assess the effect of low-vision devices on perceived reading ability. Reading performance is strongly associated with vision-related quality of life, and reading is often the primary rehabilitation goal of visually impaired individuals (Hazel et al., 2000; Stelmack et al., 2008). This was also the case with our patients, as 90% of them indicated reading improvement as the rationale for seeking low-vision services. The type of vision devices prescribed confirmed this trend, as vision aids for near vision were 9.3 times more commonly ordered than devices for distance vision.
Interestingly, after rehabilitation, our patients showed improved Modified German NEI VFQ-25 scores not only in the subscales of near tasks and reading ability, as expected, but also in social functioning. The magnitude of the change was substantial for reading ability and social functioning, suggesting that appropriate vision aids might have a much wider effect than that strictly linked to visual performance. Other studies have reported improved scores in some NEI VFQ-25 subscales after low-vision rehabilitation, such as near and distance activity (Scott et al., 1999; Stelmack et al., 2002), and general and peripheral vision (Scott et al., 1999), but none have found any change in social functioning.
How can this difference be explained? One plausible explanation could be differences in the study design and population: Stelmack et al. (2002) collected postrehabilitation ratings from the patients immediately before discharge, whereas we interviewed patients after they used vision aids in their habitual environment. Scott’s investigation had a design very similar to that of the present study, and the population was comparable to ours in terms of age, VA, and primary ocular diagnosis; nevertheless, it did not show any change in social functioning after low-vision rehabilitation (Scott et al., 1999). This could be explained by the much higher rating of vision-specific social functioning at baseline (62.9 vs. 41.3 in our study), which may make further improvement improbable. Other interventions might have had no influence on experienced social functioning or the questionnaires used in other studies failed to capture this effect. Although our questionnaire had been modified, the questions related to social functioning were identical to the German NEI VFQ-25.
Even though other studies could not show improvement in ‘social functioning’ as assessed with the NEI VFQ-25, there are studies underlining how visual impairments are associated with restrictions in participation in daily activities and therefore emphasize the importance of psychological aspects in participation (Desrosiers et al., 2009; Renaud et al., 2010; Alma et al., 2011). More recent studies also seem to support our results. In patients with age-related macular degeneration, social functioning measured using NEI VFQ-25 correlated positively not only with better VA, as in our data, but also with reading speed (Cahill et al., 2005). In older nursing-home residents, spectacle correction of refractive error was found to increase social interaction (Owsley et al., 2007), underlining the influence of visual performance on socialization.
We could not find any correlation for social functioning and age, sex, education, family situation, eye diagnosis, and systemic comorbidity. Although the exact mechanism of improved social functioning through enhanced reading performance remains unclear and needs further investigations, our data indicate that these effects might be related to low-vision rehabilitation. In fact, possible biases such as VA, general life satisfaction, depression, and anxiety were assessed and remained stable during the study. In our sample, there were no patients with recent visual loss or impairment, as indicated by the fact that 85% of them were already using some magnifying devices before our intervention. Thus, it seems unlikely that the improvement in quality-of-life indicators were just related to better coping or adaptation over time.
The present study has a number of limitations. First, it had a low response rate, as only 57% of the patients repeated the interview after rehabilitation. The main limitation of our data is the lack of a randomized control group not receiving visual rehabilitation, which indeed would have implicated ethical problems and even lower patients’ acceptance. This is especially the case after Stelmack et al. (2008) found a decline in functional ability in patients in the waiting list for visual rehabilitation, who served as controls in the LOVIT randomized clinical trial. We cannot exclude a placebo effect of visual rehabilitation in the present study. It might also be possible that the use of low-vision services offered the patient some kind of emotional support. However, it seems rather improbable that such a singular and nonprofessional emotional help would have lasted several months (quality of life was reassessed on average 4–5 months after rehabilitation). In a recently published study (Pearce et al., 2011), a significant improvement in goal difficulty after a single optometrist consultation was reported, confirming, in part, our results. In any case, further investigations are warranted to support our data.
The present findings show that proper vision aids lead to more than just improved visual performance and should encourage their early and widespread use.
The authors thank Dr I. Schmidtmann (Institute for Medical Biometry, Epidemiology and Informatics, University Medical Center, Mainz) and Prof. Dr J. Hardt (Department for Medical Psychology and Sociology, University Medical Center, Mainz) for help with the statistical analysis.
This study was supported by a grant from the Nauendorff Stiftung, Wiesbaden, Germany.
Conflicts of interest
There are no conflicts of interest.
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