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Preserving the health and well-being of older adults with visual impairment remains a challenge, particularly in light of our ageing population. The development of frailty poses a serious threat to all older adults, increasing their risk of falls, fractures, institutionalisation and mortality.1–5 Frailty is characterised by observable functional declines in the body, particularly weight loss, exhaustion, low energy expenditure, slowness and weakness,1,6,7 and has been linked to visual impairment in recent population studies.8–10
Glaucoma is a leading cause of irreversible visual impairment among older adults, leading to visual field loss, and in the later stages of the disease, to loss of central vision. As locomotion has been shown to be highly visually dependent,11,12 it is expected that mobility would become increasingly difficult with greater visual impairment. This has been shown in particular for visual field loss which results in slower walking speeds and increased number of obstacle contacts, both in general older populations13 and among those with glaucomatous visual impairment.14,15
Increasing difficulties with mobility are likely to influence participation in regular physical activity. Importantly, activity restriction among older adults has been shown to lead to reductions in physical function,16–18 and correlates with greater functional limitations and disability.19,20 As physical activity and exercise may postpone or reverse the effects of age-related loss of muscle mass and strength,21,22 early detection and prevention of frailty is an important factor in improving the health and well-being of older adults.
It is unclear, however, whether glaucomatous visual impairment is associated with reductions in physical activity or poorer functional status among older adults. In a case-control study which assessed falls and driving outcomes, basic mobility and functioning, measured using the timed up and go test, was significantly reduced for 48 glaucoma participants compared to 47 age-matched controls, but no differences were noted for self-reported physical activity levels.23 In a population study examining mobility performance, stair climbing speed among older adults with bilateral glaucoma was slower compared to those without glaucoma, but these differences were not statistically significant,14 although the findings are limited by the use of a non-standardised functional status measure. In our previous study, increased levels of visual field loss was associated with greater postural instability among older adults with glaucoma,24 which may also negatively influence participation in physical activity.
Despite the fact that frailty poses a serious threat to the health of older adults, there is also little known about the association between severity and location of visual field loss and functional status among older adults. Therefore, the aim of the current study was to examine the association between visual function, using a comprehensive battery of vision measures, and functional status in a community-dwelling sample of older adult with glaucoma.
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The demographic, medical, visual function and functional status characteristics of the 74 participants are presented in Table 1. The mean age of participants was 74.2 ± 5.9 years, with slightly more males than females. The severity of glaucomatous visual impairment, based on visual field loss, ranged from early to advanced, with IVF-60 MD scores of −4.10 ± 6.28 dB (range −28.23 to 1.59) and IVF-120 points missed of 32 ± 21 (range 6–96). Participants using topical beta-blockers had similar levels of visual field loss (IVF-60 and IVF-120; p > 0.05) and functional status (all tests; p > 0.05) compared to those not using any topical beta-blocker glaucoma medications.
Table 1. Characteristics of the study cohort (n = 74)
| Age, mean ± S.D. (range)||74.2 ± 5.9 (62 to 90)|
| Female, n (%)||35 (47%)|
|Top 5 chronic medical conditions, n (%)|
| Arthritis||38 (51%)|
| Hearing impairment||29 (39%)|
| Hypertension||29 (39%)|
| Heart disease||22 (29%)|
| History of cancer||20 (27%)|
|Number of prescription medications, median (IQR)||4 (2 to 7)|
|History of falls in the previous year, n (%)||26 (35%)|
|Fear of falling reported, n (%)||16 (22%)|
|Glaucoma medical history|
| Number of glaucoma eye drops used, median (IQR)||1 (1 to 2)|
| Time since diagnosis, years, median (IQR)||9 (4 to 15)|
| History of previous glaucoma surgery, n (%)||14 (19%)|
|Visual function measures|
| Visual acuity in better-eye, logMAR, mean ± S.D. (range)||0.06 ± 0.13 (−0.26 to 0.52)|
| Contrast sensitivity in better-eye, logCS, mean ± S.D. (range)||1.54 ± 0.17 (0.65 to 1.70)|
| IVF-60 visual field, dB, mean ± S.D. (range)||−4.10 ± 6.28 (1.59 to −28.23)|
| IVF-120 visual field, points missed, mean ± S.D. (range)||32 ± 21 (6 to 96)|
|Functional status measures|
| Physical Activity Scale for Elderly (PASE) score, mean ± S.D. (range)||128.7 ± 52.5 (37.9 to 301.3)|
| 6-min walk test, metres, mean ± S.D. (range)||503 ± 69 (342 to 650)|
| Timed-up and go test, seconds, mean ± S.D. (range)||10.1 ± 2.0 (6.8 to 15.3)|
| Lower limb strength, kg force, mean ± S.D. (range)||19.4 ± 7.8 (6 to 44)|
| Overall functional status score, mean ± S.D. (range)||0.00 ± 0.71 (−1.75 to 1.62)|
The age and gender adjusted correlations between the visual function measures and functional status outcomes are shown in Table 2. PASE scores were significantly associated with contrast sensitivity (r = 0.24) and all of the visual field measures (r=|0.23| to |0.31|). Timed up and go performance was associated with inferior IVF-120 (r = 0.23), while overall functional status score was only associated with IVF-60 (r = 0.25). In all cases, poorer visual function was associated with reduced performance on these measures. No significant associations were found for any of the vision measures and the 6-min walk test or lower limb strength.
Table 2. Correlations coefficients of functional status outcomes and visual function measures, adjusted for age and gender (n = 74)
|Visual Function Measure||PASE score||6-min walk test||Timed-up and go test||Lower limb strength||Overall functional status score|
|Visual Acuity, better-eye (logMAR)†||−0.15||0.10||−0.13||0.04||−0.15|
|Contrast Sensitivity, better-eye (logCS)‡||0.24*||−0.01||−0.07||0.07||0.13|
|IVF-60, full field (dB)‡||0.29*||−0.03||−0.06||0.06||0.15|
|IVF-60, inferior field (dB)‡||0.31**||0.08||−0.17||0.11||0.25*|
|IVF-60, superior field (dB)‡||0.25*||−0.07||−0.03||0.02||0.12|
|IVF-120, full field (points missed)†||−0.28*||−0.06||0.17||−0.14||−0.24*|
|IVF-120, inferior field (points missed)†||−0.27*||−0.14||0.23*||−0.20||−0.31**|
|IVF-120, superior field (points missed)†||−0.25*||0.03||0.09||−0.06 ||−0.14|
The loadings of the contrast sensitivity and visual field measures used to generate the three vision factors are shown in Table 3.
Table 3. The loading of the visual function measures on the three factors (principal components factors analysis with varimax transformation; n = 74)
| ||Factor 1, ‘superior field’||Factor 2, ‘inferior field’||Factor 3, ‘contrast’|
|Contrast Sensitivity, better-eye (logCS)||0.34||0.34||0.87|
|IVF-120, inferior field (points missed)||−0.41||−0.86||−0.25|
|IVF-120, superior field (points missed)||−0.88||−0.37||−0.26|
|IVF-60, inferior field (dB)||0.37||0.78||0.47|
|IVF-60, superior field (dB)||0.83||0.37||0.36|
|% Variance explained (rotated solution)†||37.5%||34.8%||24.9%|
The results of the multivariate linear regression analyses showed that poorer performance in the contrast factor was associated with lower PASE scores and overall functional status scores, adjusted for age and gender (Table 4). Furthermore, poorer performance in the inferior field factor was associated with slower timed-up and go scores, weaker lower limb strength and lower overall functional status scores. While poorer performance in the inferior field factor was associated with a longer 6-min walk distance, this failed to reach statistical significance. The superior field factor was not independently associated with any of the functional status outcomes. The vision factors explained the greatest amount of variance for the overall functional status scores (10.8%) and for the PASE scores (10.2%).
Table 4. Multivariate regression findings for functional status outcomes on the vision factors, adjusted for age and gender (n = 74)
|Vision factor||PASE score||6-min walk test (m)|
|Regression Coefficient (95% CI)†||p-Value‡||Regression Coefficient (95% CI)†||p-Value‡|
|Contrast factor||−11.5 (−0.1 to−22.8)||0.047||−8.0 (5.3 to −21.3)||0.24|
|Superior field factor||−9.5 (2.2 to −21.2)||0.11||10.6 (24.3 to −3.1)||0.13|
|Inferior field factor||−9.2 (2.0 to −20.4)||0.11||−11.9 (1.2 to −25.0)||0.076|
|Variance explained by vision factors (%)||10.2%|| ||6.1%|| |
|Variance explained by the full model (%)||14.7%|| ||32.7%|| |
|Vision factor||Timed-up and go test (sec)||Lower limb strength (kg force)||Overall functional status score|
|Regression Coefficient (95% CI)†||p-Value‡||Regression Coefficient (95% CI)†||p-Value‡||Regression Coefficient (95% CI)†||p-Value‡|
|Contrast factor||0.2 (0.6 to −0.1)||0.23||−1.1 (0.4 to −2.5)||0.15||−0.2 (−0.02 to−0.3)||0.028|
|Superior field factor||−0.1 (0.3 to −0.5)||0.54||0.3 (1.8 to −1.2)||0.65||0.02 (0.16 to −0.11)||0.76|
|Inferior field factor||0.4 (0.1 to 0.8)||0.020||−1.5 (−0.1 to−2.9)||0.039||−0.2 (−0.1 to−0.3)||0.004|
|Variance explained by vision factors (%)||6.1%|| ||5.5%|| ||10.8%|| |
|Variance explained by the full model (%)||36.7%|| || ||36.6%|| ||39.0%|
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In this cross-sectional study, increased visual impairment was significantly associated with lower levels of functional status among community-dwelling older adults with glaucoma. Specifically, lower levels of visual function were associated with slower timed up and go performance, weaker lower limb strength, lower self-reported physical activity, and lower overall functional status scores. Of the visual factors examined, the contrast and inferior field factors were the strongest predictors of these outcomes, while the superior visual field factor was not related to any of the functional status outcomes. This is the first study to show a significant association between functional status and visual impairment among older adults with glaucoma, and the findings highlight the importance of vision in physical activity and physical functioning.
The mechanism of the relationship between glaucomatous visual impairment and functional status, albeit speculative, is that the glaucomatous visual loss may initiate restriction of physical activity due to difficulties in mobility, with subsequent declines in physical function due to inactivity. Previous studies have demonstrated significant reductions in mobility performance with more extensive visual field loss among older adults with glaucoma,14,15 other eye disease populations46,47 and general older populations.13 Experimental studies of younger normally sighted participants have also highlighted the negative impact of simulated visual field loss on mobility in virtual environments,48 and in gait behaviour, where more cautious gait strategies are adopted in the presence of field loss.49,50
Given that physical inactivity precedes reductions in physical functions,16,17 it was not surprising that stronger associations were found between the visual function measures and PASE scores, rather than with the performance-based measures. This was also evident in the multivariate models, where the vision factors explained nearly double the amount of variance in PASE scores (10.2%) than did the performance-based measures (5.5–6.1%).
Furthermore, this cohort of independent, community-dwelling adults had similar, if not higher, levels of physical function to other studies, which may have limited the strength of the correlations. Direct comparisons with other studies are difficult, however, due to variations in the age and health status of populations between studies. The mean PASE scores in this study were higher than other studies, including community-dwelling adults aged 65 years and over (pooled mean 106.4 ± 57.3)51 and glaucoma patients aged over 50 years (median 117, range 25–253).23 The mean 6-min walk distances were also longer than that recorded in non-institutionalized older adults older adults (pooled mean 406 ± 127 m),36 which is not surprising given that 30% of the participants in this study used a walking aid. Timed-up and go test scores were also comparable to research which included glaucoma patients (11 ± 3 s),23 and lower limb strength was similar to findings from population studies (pooled mean 23.8 ± 11.0 kg force).52
Our finding of an association between inferior field loss and functional status, rather than superior field loss, is consistent with studies which highlight the importance of this region of the visual field.12,13,53 When walking, individuals fixate approximately two steps ahead,54 and the inferior visual field contributes a major proportion of visual information used in lower limb movements, foot placement and obstacle detection.12 Studies involving adults with visual impairment have reported that greater loss in the central and inferior visual field regions results in reduced mobility performance.13,53 Furthermore, research has demonstrated that inferior visual field loss was associated with increased postural sway, reflecting greater instability, to a greater extent than did superior visual field loss.24
The contrast factor was also a significant predictor of a number of functional status outcomes, independent of the field factors, in our glaucoma group. This is consistent with previous research involving participants with other eye diseases and in a general aged population cohort, which demonstrated associations between contrast sensitivity loss and mobility performance13,46 and postural stability.45,55 It was not surprising that the association between visual acuity measures and functional status measures were weak, given the narrow range of visual acuity loss in this cohort, and hence low variability in these measures. Furthermore, visual acuity has not been shown to be strongly linked to mobility performance in previous studies involving heterogeneous visually impaired populations.13,46,47
The findings of this study are important, as the development of frailty increases the likelihood of serious adverse health outcomes, particularly falls, fractures, institutionalisation and mortality.1,2,5,33,56 Declines in physical function, functional limitations and frailty have been linked to central vision loss among older adults,8–10 and the present study provides additional evidence to support links between physical inactivity, functional declines and visual impairment among older adults with glaucoma.
Physical inactivity is likely to be an important link to the functional declines seen in this population. While physical activity and exercise hold great potential for improving and maintaining physical function among older adults,57 they may be challenging for visually impaired populations. Campbell et al.58 showed a tendency (which did not reach statistical significance) for a higher rate of falls among older adults with central vision loss who received an exercise program, compared to those not receiving the program. Their findings suggest that regular physical activity programs for visually impaired populations may be problematic, as these exercise programs had been effective in improving physical function and reducing falls among general community-dwelling older women in a previous study.59 A challenge for future research is to develop innovative physical activity programs which have the capacity to improve physical function and reduce frailty and falls for adults with visual impairment.
The strengths of the current study include the use of a battery of standardised visual function measures, including binocular integrated visual field measures, and the use of standardised measures of physical activity and functional performance designed for older adults. A potential limitation of this study, however, is the cross-sectional design, which precludes inferences about causality in the relationship between visual impairment and functional status. We cannot exclude the possibility that there was some recruitment bias towards more highly functioning participants, who were able to attend the research visits; this may have resulted in conservative estimates of the association between visual impairment and functional status. Furthermore, the regression coefficients need to be interpreted with caution, given the small sample size.
In summary, the present study provides important insights into the association between vision impairment and functional status among older adults with glaucoma, and identifies potential challenges in the prevention of functional decline. Visual field loss has been identified as an independent risk factor for falls and fractures among older adults,60–62 and innovative falls prevention programs for this population should include balance, strength and exercise training,63 to improve lower limb strength, postural stability and minimise frailty. A better understanding of the relationship between vision impairment and physical activity will help guide future strategies to promote and maintain the health and well-being of older adults with glaucoma.