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Glaucoma  |   November 2013
The Association Between Visual Field Defect Severity and Fear of Falling in Primary Open-Angle Glaucoma
Author Affiliations & Notes
  • Kenya Yuki
    Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
    Iidabashi Eye Clinic, Tokyo, Japan
  • Sachiko Tanabe
    Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
    Tanabe Eye Clinic, Yamanashi, Japan
  • Keisuke Kouyama
    The Center for Clinical Research, Keio University School of Medicine, Tokyo, Japan
  • Kazumi Fukagawa
    Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
    Iidabashi Eye Clinic, Tokyo, Japan
  • Miki Uchino
    Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
  • Masaru Shimoyama
    Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
  • Naoki Ozeki
    Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
  • Daisuke Shiba
    Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
  • Yoko Ozawa
    Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
  • Takayuki Abe
    The Center for Clinical Research, Keio University School of Medicine, Tokyo, Japan
  • Kazuo Tsubota
    Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
  • Correspondence: Kenya Yuki, Department of Ophthalmology, Keio University School of Medicine, Shinanomachi 35, Shinjuku-ku, Tokyo, Japan; yukikenya114@gmail.com
Investigative Ophthalmology & Visual Science November 2013, Vol.54, 7739-7745. doi:10.1167/iovs.13-12079
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      Kenya Yuki, Sachiko Tanabe, Keisuke Kouyama, Kazumi Fukagawa, Miki Uchino, Masaru Shimoyama, Naoki Ozeki, Daisuke Shiba, Yoko Ozawa, Takayuki Abe, Kazuo Tsubota; The Association Between Visual Field Defect Severity and Fear of Falling in Primary Open-Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(12):7739-7745. doi: 10.1167/iovs.13-12079.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose.: To determine if glaucomatous visual field defect severity is associated with fear of falling.

Methods.: This is a cross-sectional study. A total of 387 consecutive subjects with POAG were enrolled in this study along with 293-ocular disease-free control subjects, who were screened at the same institutions. We defined mild POAG as MD of −6 dB or better, moderate POAG as MD of −6 to −12 dB, and severe POAG as MD of −12 dB or worse in the better eye. All participants were requested to answer a questionnaire on fear of falling. Associations between POAG severity and the prevalence of fear of falling were evaluated with the Cochran-Armitage trend test. Multivariable factors including age-adjusted odds ratios (ORs) for the prevalence of fear of falling and 95% confidence intervals (CIs) were evaluated with logistic regression models.

Results.: The prevalence of fear of falling was 35/293 (11.9%) in the control group, 38/313 (12.1%) in the mild POAG group, 12/48 (25.0%) in the moderate POAG group, and 6/26 (23.1%) in the severe POAG group, and the trend was statistically significant (P = 0.028 Cochran-Armitage trend test). The adjusted ORs for prevalence in the mild, moderate, and severe POAG groups compared with that in the control group were 1.44 (95% CI: 0.83–2.51), 2.33 (95% CI: 1.00–5.44), and 4.06 (95% CI: 1.39–11.90), respectively.

Conclusions.: Among patients with POAG, the severity of visual field defects is associated with fear of falling. (http://www.umin.ac.jp/ctr/index.htm number, UMIN000005574.)

Introduction
Falls are among the most common physical threats for the elderly. Previous studies estimate that about 30% of individuals over the age of 75 experience falls at least once per year; 10% to 20% of these falls lead to injury, and 5% to 6% result in fracture. 1,2 Falls result not only in physical injury, but also have psychological consequences (e.g., fear of falling). Fear of falling has been defined as a concern about falling that makes an individual avoid activities that he or she actually remains capable of taking part in. 3 Fear of falling is associated with self-imposed restrictions on activities, 4,5 depression, 6,7 reduced mobility levels, 8 increased risk of actual falling, 9 and reduced health-related quality of life (QOL). 7  
Glaucoma is the second leading cause of blindness in the world, affecting approximately 5 million adults globally. 10 Glaucomatous optic neuropathy is a disease that involves slow, progressive loss of retinal ganglion cells, resulting in a concomitant pattern of peripheral and central visual field loss. In one study, subjects with glaucoma were found to be over three times more likely to have fallen in the previous year than healthy controls. 11 However, the association between fear of falling and the severity of glaucomatous visual field defects is not yet fully understood. 12,13 Ramulu et al. 12 compared 83 glaucoma subjects with 60 subjects suspected of having glaucoma and concluded that fear of falling increased with greater visual field loss (β = −0.52 logits per 5-dB decrement in the better eye visual field). However, Turano et al. 13 failed to show any significant association between glaucoma and fear of falling. 
The aim of this study was to investigate the prevalence of fear of falling among patients with POAG in comparison with comparably aged healthy subjects, and to examine the association between the prevalence of fear and disease severity. Factors that affect fear of falling among POAG patients were also investigated. 
Methods
The procedures used in this study conformed to the tenets of the Declaration of Helsinki and to national (Japanese) and institutional (Keio University School of Medicine) regulations. The study was approved by the ethics committee of Keio University School of Medicine (#2010293). All study subjects signed written informed consent prior to enrollment after explanation of the nature and possible consequences of the study. The study was preregistered in the University Hospital Medical Information Network (UMIN) Clinical Trial Registry (UMIN000005574, http://www.umin.ac.jp/ctr/index.htm). 
Study Design and Subject Enrollment
A total of 943 consecutive Japanese patients aged between 40 and 85 years who visited Keio University Hospital (Tokyo, Japan), Iidabashi Eye Clinic (Tokyo, Japan), or Tanabe Eye Clinic (Yamanashi, Japan) between May 1, 2011 and November 30, 2011 were screened for eligibility as subjects for this multicenter, cross-sectional study. Subjects with POAG were screened at the glaucoma clinics of the three institutions, and the control subjects were screened at the general outpatient clinics of the same institutions. 
Evaluation of Glaucoma Subjects
The glaucoma subjects were screened for eligibility with a battery of ophthalmic examinations: slit-lamp biomicroscopy, funduscopy, gonioscopy, IOP measurements with Goldmann applanation tonometry, and visual field examination with a Humphrey visual field analyzer using the 30-2 or 24-2 Swedish Interactive Threshold Algorithm standard strategy (Carl Zeiss Meditec, Dublin, CA). The findings were analyzed by ST, NO, Shingo Hosoda, MS, and KY, all of whom subspecialize in glaucoma. Reliability was confirmed at rates of less that 20% fixation losses, less than 33% false-positive results, and less than 33% false-negative results. In this study, we requested that the patients be re-evaluated for visual field defects until the reliability met prespecified criteria. Therefore, no subjects were excluded for failure to meet the visual field test criteria. 
POAG was diagnosed on the basis of the presence of the following three sets of findings: (1) glaucomatous optic cupping represented by notch formation, generalized enlargement of cupping, senile sclerotic disc or myopic disc, or nerve fiber layer defects, (2) typical glaucomatous visual field defects such as Bjerrum scotoma, nasal step, or paracentral scotoma compatible with optic disc appearance, and (3) open angle observed on gonioscopy. 
Evaluation of Control Subjects
We recruited the control subjects without POAG at the general outpatient clinics of the same institutions: Keio University Hospital, Tanabe Eye Clinic, and Iidabashi Eye Clinic. They mostly consisted of individuals who visited the clinics for their annual eye examination, or those with an outer adnexal disease. The control subjects were evaluated by an ophthalmic examination that included best-corrected visual acuity measurements, autorefractometry, slit-lamp biomicroscopy, funduscopy, and IOP measurements with a noncontact tonometer or Goldmann applanation tonometer. Control subjects satisfied both of the following vision-related criteria: (1) free of ocular fundus disease that may affect visual function, and (2) best-corrected visual acuity in both eyes of less than 0.25 logarithm of the minimum angle of resolution (LogMAR) visual acuity. 
Exclusion Criteria
Subjects with an ophthalmologic disease other than POAG that could potentially compromise visual acuity or contribute to visual field loss, such as secondary glaucoma or AMD, were excluded. Subjects with a LogMAR best-corrected visual acuity of 0.20 or more were excluded. Subjects were also excluded if they were unable to walk unassisted or had any mental disease that prevented them from understanding the questionnaire. Of the 943 subjects screened, 263 were excluded (Supplementary Table S1). We used a cut-off value of 0.20 LogMAR, not 0.301 LogMAR, to focus on the association between the glaucomatous visual field defect and fear of falling, while avoiding the effect of poor best-corrected visual acuity. 
Evaluation of Fear of Falling
All participants were requested to answer a questionnaire in Japanese that contained the following questions (translated): 
  1.  
    Can you walk without assistance? (Yes/No)
  2.  
    Do you use a cane or any kind of walking aid? (Yes/No)
  3.  
    How long do you spend walking on average per day? (The number of minutes was recorded.)
  4.  
    Are you afraid of falling? (Not at all; Not much; Afraid; Very afraid)
  5.  
    Have you had any falls in the last year? (Yes/No)
In addition, demographic information was elicited on age, sex, height, weight, alcohol intake, smoking history, current illnesses, and medical history (including medications taken orally). 
In our dichotomous analysis, those who answered “Afraid” or “Very afraid” to question (4) were considered to have fear of falling, and those who answered “Not at all” or “Not much” were considered to have no fear. The question “Are you afraid of falling?” was used in previous studies to provide a hierarchy of fear of falling. 14,15  
Glaucoma Severity Grading
For the purposes of this study, we defined mild POAG as a visual field defect corresponding to an MD of −6 dB or better in the better eye, moderate POAG as corresponding to an MD of −6 to −12 dB, and severe POAG as an MD of −12 dB or worse. 16 The eye with better visual field was defined as the eye with the higher (i.e., less negative) MD. 
Statistical Analysis
Descriptive statistics were calculated for the demographic, medical, and visual function variables. Homogeneity of distributions between the POAG and control groups was examined with ANOVA or Fisher's exact test, depending on the variables. Associations between POAG severity and the prevalence of fear of falling were evaluated with the Cochran-Armitage trend test, for which exact statistics were used. Pair-wise comparisons of the prevalence of fear of falling between the control group and the three POAG groups combined were performed with the χ2 test. 
For sensitivity analyses, adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated with logistic regression models to examine the effects of confounding factors on the unadjusted results. We used forward stepwise selection to determine which candidate variables were possibly associated with fear of falling (P < 0.1), and thus entered into the model. Factors included glaucoma severity, age, sex, body mass index (BMI), alcohol intake, current smoking habit, presence of diabetes mellitus, hypertension, depression, and presence of comorbid illnesses, previous history of falls, and (1) best-corrected visual acuity in the better eye or (2) that in the worse eye. 
To examine the association between glaucoma severity and fear of falling, Spearman's correlation coefficient was used to analyze the association between MD in the better eye and the degree of fear of falling. 
The difference in walking time between subjects with fear of falling and those without was examined with the Mann–Whitney U test. Multiple linear regression analysis with stepwise variable selection was used to explore independent predictor variables for minutes spent walking per day (factors: fear of falling, age, sex, BMI, best-corrected visual acuity in the worse eye, history of falls, and comorbid illnesses). We performed a logarithmic transformation of the minutes spent walking per day to obtain a normal distribution for linear regression analysis. 
A P value of less than 0.05 was considered to be statistically significant. All data were analyzed with IBM SPSS statistics software version 21.0 (IBM Japan, Tokyo, Japan). 
Results
A total of 387 POAG patients divided into three groups according to POAG severity (165 men, 222 women; age: 65.4 ± 10.7 years) and 293 control subjects (113 men, 180 women; age: 67.6 ± 11.1 years) were evaluated in this study. All participants were Asian, and their demographic characteristics are summarized in Table 1. There were statistically significant differences in age, sex, and alcohol intake among the four groups. 
Table 1
 
Characteristics of Subjects
Table 1
 
Characteristics of Subjects
Controls Mild Glaucoma Moderate Glaucoma Severe Glaucoma P Value
Number 293 313 48 26
Age 67.6 ± 11.1 64.8 ± 10.5 68.2 ± 11.8 67.3 ± 11.0 0.007*
Sex, M/F 113/180 133/180 26/22 6/20 <0.001†
BMI 22.5 ± 3.2 22.4 ± 3.1 22.5 ± 3.0 22.0 ± 2.3 0.89*
Alcohol drinker 118 (40.3%) 148 (47.3%) 22 (45.8%) 19 (73.1%) 0.009†
Current smoker 33 (11.3%) 35 (11.2%) 8 (16.7%) 6 (23.1%) 0.23†
Total comorbid illnesses
 0 228 (77.8%) 256 (81.8%) 33 (68.8%) 20 (76.9%) 0.36*
 1 61 (20.8%) 52 (16.6%) 13 (27.1%) 5 (19.2%)
 2 or more 4 (1.4%) 5 (1.6%) 2 (4.2%) 1 (3.8%)
Walking time per day, min 83.7 ± 90.9 83.0 ± 93.4 76.0 ± 73.4 67.9 ± 69.0 0.80*
History of falls 50 (17.1%) 50 (16.0%) 12 (25.0%) 2 (7.7%) 0.26†
BCVA in the better eye, LogMAR 0.01 ± 0.03 0.01 ± 0.02 0.01 ± 0.03 0.01 ± 0.03 0.21*
BCVA in the worse eye, LogMAR 0.02 ± 0.04 0.02 ± 0.04 0.03 ± 0.04 0.02 ± 0.04 0.74*
MD in the better eye, dB −1.4 ± 1.8 −8.0 ± 1.9 −16.9 ± 4.5 <0.001*
MD in the worse eye, dB −6.0 ± 5.7 −14.1 ± 5.2 −21.0 ± 4.9 <0.001*
use of topical Beta blockers 141 (45.0%) 19 (39.6%) 18 (69.2%) 0.04†
The difference in prevalence of fear of falling between the control group and the three POAG groups combined was not statistically different (controls: 35/293 [11.9%], POAG groups combined: 56/331 [14.5%], P = 0.36). However, the association between prevalence of fear of falling and POAG severity was statistically significant (P = 0.028, Cochran-Armitage trend test), as shown in Table 2
Table 2
 
Number of Subjects by Group With Fear of Falling
Table 2
 
Number of Subjects by Group With Fear of Falling
Controls Mild Glaucoma Moderate Glaucoma Severe Glaucoma P Value
Prevalence of fear of falling 35/293 = 11.9% 38/313 = 12.1% 12/48 = 25.0% 6/26 = 23.1% 0.035*; 0.028†
For sensitivity analyses, adjusted ORs and 95% CIs were estimated with logistic regression models. The adjusted ORs for the prevalence of fear of falling in the mild, moderate, and severe POAG groups compared with that in the control group were 1.44 (95% CI: 0.83–2.51), 2.33 (95% CI: 1.00–5.44), and 4.06 (95% CI: 1.39–11.90), respectively. The other factors examined with respect to fear of falling are shown in Table 3
Table 3
 
Risk Factors for Fear of Falling in Subjects With or Without Glaucoma: Crude and Multivariable Adjusted Results
Table 3
 
Risk Factors for Fear of Falling in Subjects With or Without Glaucoma: Crude and Multivariable Adjusted Results
Crude Age- and Sex-Adjusted Multivariable Adjusted
Mild glaucoma in the better eye (ref control) 1.02 (0.62–1.66) 1.47 (0.84–2.48) 1.44 (0.83–2.51)
Moderate glaucoma in the better eye (ref control) 2.46 (1.17–5.16) 2.51 (1.14–5.55) 2.33 (1.00–5.44)
Severe glaucoma in the better eye (ref control) 2.21 (0.83–5.88) 3.04 (1.06–8.69) 4.06 (1.39–11.90)
BCVA in the better eye (LogMAR per 0.1 increment) 2.61 (1.30–5.23) 1.50 (0.72–3.14)
BCVA in the worse eye (LogMAR per 0.1 increment) 2.12 (1.40–3.21) 1.58 (1.02–2.46)
Age (per 1 y) 1.08 (1.05–1.11) * 1.08 (1.05–1.11)
Female sex (male as ref) 1.66 (1.06–2.61) * 1.87 (1.11–3.13)
BMI, kg/m2 0.99 (0.92–1.06) 1.01 (0.93–1.09)
Presence of hypertension 1.06 (0.67–1.69) 0.78 (0.48–1.26)
Presence of diabetes mellitus 1.11 (0.58–2.14) 1.16 (0.59–2.31)
Presence of cerebral infarction 2.48 (0.65–9.51) 2.53 (0.63–10.09) *
Presence of depression 2.80 (0.96–8.13) 3.61 (1.15–11.3)
Presence of comorbid illnesses (yes or no) 2.48 (1.54–3.98) 2.28 (1.39–3.73) 2.03 (1.20–3.43)
Use of topical beta blockers 1.02 (0.58–1.80) 1.15 (0.64–2.07) *
Use of antihypertensives 1.22 (0.77–1.95) 0.91 (0.56–1.48) *
Use of sleeping aids 1.74 (0.73–4.11) 1.15 (0.47–2.83) *
Current smoker (never or former as ref) 0.44 (0.44–1.79) 1.19 (0.56–2.53)
Alcohol drinker (non-drinker as ref) 0.62 (0.39–0.98) 0.97 (0.57–1.67)
History of falls 6.16 (3.81–9.95) 5.39 (3.23–8.91) 5.22 (3.11–8.75)
Mean deviation in the better eye was significantly associated with the degree of fear of falling (P = 0.006, R = −0.140, Spearman's correlation coefficient). Sensitivity analyses were performed in the subjects with glaucoma adjusted for MD values as a continuous variable to clarify the effects of visual field defects. Mean deviation in the better eye was significantly associated with the prevalence of fear of falling in the subjects with glaucoma (ORs: 0.93 [95% CI: 0.88–0.99] per 1-dB increment). Other risk factors for the prevalence of fear of falling in subjects with glaucoma are shown in Table 4
Table 4
 
Risk Factors for Fear of Falling: Crude and Multivariable Adjusted Results in Subjects With Glaucoma
Table 4
 
Risk Factors for Fear of Falling: Crude and Multivariable Adjusted Results in Subjects With Glaucoma
Crude Age- and Sex-Adjusted Multivariable Adjusted
MD in the better eye (per 1-dB increment) 0.93 (0.89–0.98) 0.94 (0.89–0.99) 0.93 (0.88–0.99)
MD in the worse eye (per 1-dB increment) 0.96 (0.93–1.00) 0.97 (0.93–1.01) *
BCVA in the better eye (LogMAR per 0.1 increment) 5.69 (1.97–16.52) 3.07 (0.98–9.63)
BCVA in the worse eye (LogMAR per 0.1 increment) 2.83 (1.67–4.80) 2.19 (1.25–3.84)
Age (per 1 y) 1.08 (1.04–1.11) * 1.06 (1.03–1.10)
Female sex (male as ref) 1.68 (0.95–2.97) *
BMI, kg/m2 0.97 (0.88–1.07) 0.98 (0.89–1.09)
Presence of hypertension 0.73 (0.38–1.40) 0.55 (0.28–1.08)
Presence of diabetes mellitus 1.35 (0.64–2.87) 1.18 (0.54–2.61)
Presence of cerebral infarction 1.50 (0.31–7.25) 1.43 (0.29–7.16) *
Presence of depression 6.31 (1.53–26.00) 6.85 (1.46–32.19) 7.18 (1.58–32.53)
Presence of comorbid illness (yes or no) 2.57 (1.39–4.75) 2.31 (1.21–4.41)
Use of topical beta blockers 1.02 (0.58–1.80) 1.15 (0.64–2.07) *
Use of antihypertensives 0.89 (0.47–1.68) 0.65 (0.34–1.27) *
Use of sleeping aids 2.25 (0.69–7.32) 1.69 (0.48–5.95) *
Current smoker (never or former as ref) 0.99 (0.42–2.32) 1.45 (0.58–3.60) *
Alcohol drinker (non-drinker as ref) 0.82 (0.46–1.44) 1.22 (0.65–2.31) *
History of falls 4.95 (2.65–9.24) 3.96 (2.06–7.62) 4.28 (2.20–8.34)
The subjects with fear of falling spent significantly less time walking per day than those without (P = 0.002, Mann–Whitney U test, Figure). Multiple linear regression analysis with stepwise variable selection was used to explore independent predictors of time spent walking per day. The candidate predictors were fear of falling, age, sex, BMI, the presence of comorbid illness, best-corrected visual acuity in the worse eye, and history of falls. In the final model, fear of falling (β = −0.118, P = 0.002) and the presence of comorbid illness (β = −0.082, P = 0.033) were selected as predictors. 
Figure
 
Walking time per day was significantly less in subjects with fear of falling than in those without (*P = 0.002, Mann–Whitney U test).
Figure
 
Walking time per day was significantly less in subjects with fear of falling than in those without (*P = 0.002, Mann–Whitney U test).
Discussion
Fear of Falling and Glaucomatous Visual Field Defects
In this study, we showed that the severity of glaucomatous visual field defects, as a categorical variable, was significantly associated with fear of falling in subjects with or without glaucoma. The adjusted ORs for fear of falling in our moderate and severe POAG groups were 2.3 times and 4.1 times higher, respectively, than that for the control subjects, and the trend was statistically significant. In addition, we were able to show an association between MD values as a continuous variable and the prevalence of fear of falling in subjects with POAG after adjustment for confounders. 
Only one previous report has examined the association between visual field defect severity and fear of falling. Ramulu et al. 12 recently reported that glaucoma subjects expressed stronger fear of falling than controls (β = −1.20 logits, P = 0.001), and that fear of falling increased with greater visual field loss (β = −0.52 logits per 5-dB decrement in the better eye's visual field MD, P = 0.001). Our results agree well with Ramulu's. In our study, MD in the better eye was significantly associated with the prevalence of fear of falling in the subjects with glaucoma (ORs: 0.93 per 1-dB increment in the better eye). 
By contrast, Turano et al. 13 failed to show any association between glaucoma and fear of falling (prevalence of fear of falling: 13/47 [28%] in the glaucoma group, 11/47 [23%] in the control group, P = 0.65). The reason for the discrepancy between Turano's results and ours/Ramulu's is not clear. We showed that fear of falling is associated not with the presence of glaucomatous visual field defects, but with the severity of those defects. It is possible that subjects with mild visual field defects in the better eye do not notice them in daily life and do not feel any fear of falling until the defects become moderate to severe. Therefore, simply comparing controls and subjects with any severity of glaucoma may not reveal any significant difference in the prevalence of fear of falling. 
Factors Associated With Fear of Falling
In our study, a worse visual field in the better eye, a history of falls, increased age, being female, the presence of comorbid illnesses, and depression were recognized as factors associated with fear of falling. Falls, increased age, female sex, and poor health status have been previously reported to be associated with fear of falling. 9,1720  
Depression may also play a role in fear of falling among patients with POAG, as suggested by previous studies. 21 Glaucoma is certainly associated with depressive symptoms. 22 For example, Wang et al. 22 reported that glaucoma was a significant predictor of depression after adjusting for confounding factors (OR 1.8 [95% CI: 1.2–2.8]) in a population-based study. Depression causes individuals to lose confidence in their ability to undertake physical activities, which in turn may result in fear of falling. 
Fear of Falling and Mobility Performance in Subjects With Glaucoma
In this study, both univariate and multivariate analyses showed that fear of falling was associated with reduced time spent walking. Fear of falling is reported to be associated with walking disabilities. 20,23 Rochat et al. 23 reported that fear of falling was independently associated with reduced gait performance in such areas as stride velocity, stride length, and cadence. Deshpande et al. 20 reported that in their prospective cohort study fear of falling was an independent predictor of reduced physical function, including walking. 
Glaucomatous visual field defects are reported to be associated with reduced mobility performance. 2426 Ramulu et al. 26 reported that bilateral visual field loss due to glaucoma was associated with fewer walking steps per day (10% fewer steps per day [95% CI, −16% to −5%, P = 0.001] with each 5-dB decrement). However, the pathomechanism of this is not well understood. In our study, fear of falling was independently associated with reduced time spent walking. These results suggest that fear of falling is a plausible pathway from glaucomatous visual field defects to decreased mobility: glaucomatous visual field defects cause fear of falling, which in turn results in reduced mobility, restriction of physical activity, 2426 and lower QOL. 27  
Fear of Falling as a Modifiable Risk Factor for Low QOL in Glaucoma Subjects
Fear of falling is reported to be modifiable. 2830 Gusi et al. 28 evaluated the effect of balance training in 40 older people with fear of falling in a randomized controlled trial, and reported that the exercise group showed significantly less fear of falling and improved dynamic balance compared with the control group. Patients with severe glaucomatous visual field defects tend to restrict their daily activities. If this tendency is caused by visual field defect-induced fear of falling, it should be possible to reverse it by reducing their fear of falling. 
The factors we found to be associated with fear of falling among the subjects with POAG were a history of falls, increased age, being female, the presence of comorbid illnesses, and the presence of depression. Ophthalmologists should pay more attention to these factors, because POAG patients with any of these risk factors are more likely to have fear of falling that restricts their daily lives, even when they are physically sound. Currently, there is no known effective medical intervention for fear of falling due to glaucomatous visual field loss. However, reducing fear of falling in patients with glaucoma may be a novel approach to improving QOL in those with severe visual field defects. Rehabilitation, low-vision care, and patient education are possible methods for that purpose, but the effectiveness of these approaches must be tested in future clinical trials. 
Limitations of Our Study
Our study has several limitations. First, we used a single question (“Are you afraid of falling?”) as the measure to evaluate the main outcome variable. Subjects may, however, have answered “Yes” to this question, not because he or she was particularly afraid of falling, but because of general anxiety about many things, including falling. Depression, anxiety, and glaucoma are related. 31,32 To distinguish fear of falling from general anxiety, more specific measures such as the Fall Efficacy Scale (FES) 23,33,34 and the Activities-Specific Balance Confidence Scale (ABC scale), 34 could be included in evaluating the fear of falling in subjects with glaucoma in a future study. 
The single question has another limitation. The approach of using a single question to determine fear of falling has been shown to be less sensitive than other more comprehensive measures such as the FES 23,33,34 and the ABC Scale. 34 As a result, the associations we found may be less robust than they would have been if we had used a more detailed scale. 
Second, the prevalence of fear of falling in our control and glaucoma subjects was 11.9% and 14.5%, respectively. These are lower rates than those of previous population-based studies that addressed fear of falling in North America (36.2%, 15 30.6%, 19 and 31.0% 18 ). There are two possible explanations for this discrepancy apart from socioeconomic differences. First, we focused on younger populations, including subjects between 40- and 85-years old. Increased age is a significant risk factor for fear of falling. 9,17,35 Most previous population-based studies examined older populations that included subjects older than 85 and excluded those younger than 59. This could easily account for the lower prevalence of fear of falling in our study. Second, to investigate the association between visual field defects and fear of falling we excluded subjects with visual acuity of 0.20 LogMAR or more, and subjects with ocular diseases other than glaucoma, such as AMD. Visual impairment is associated with fear of falling, 17,35 so our selection criteria could also explain the lower prevalence in our study. 
A third limitation is that we did not evaluate the visual field in the control subjects. We assumed that their visual field was normal based on the normal appearance of the optic nerve. Visual field testing should be performed in the control subjects in future studies. 
Another limitation is the accuracy of the self-reported walking time per day. We did not validate it or check its reliability. Therefore, the self-reported walking time per day may be different from the true walking time. 
Ours was a cross-sectional study and was not designed to determine the causal association between visual field defects and fear of falling. Future longitudinal studies (such as cohort studies) would provide stronger evidence of causality. 
We showed that glaucomatous visual field defect severity is significantly associated with fear of falling. Preventing the progression of visual field defects may reduce fear of falling in patients with glaucoma, which may in turn result in increased walking time, more active daily lives, healthier lifestyles, and improved QOL. Reducing fear of falling may be a new approach to achieving better QOL among glaucoma patients with severe visual field defects. The association between fear of falling and glaucoma severity is worthy of further investigation in future studies. 
Supplementary Materials
Acknowledgments
Disclosure: K. Yuki, None; S. Tanabe, None; K. Kouyama, None; K. Fukagawa, None; M. Uchino, None; M. Shimoyama, None; N. Ozeki, None; D. Shiba, None; Y. Ozawa, None; T. Abe, None; K. Tsubota, None 
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Footnotes
 KY and ST contributed equally to the work presented here and should therefore be regarded as equivalent authors.
Figure
 
Walking time per day was significantly less in subjects with fear of falling than in those without (*P = 0.002, Mann–Whitney U test).
Figure
 
Walking time per day was significantly less in subjects with fear of falling than in those without (*P = 0.002, Mann–Whitney U test).
Table 1
 
Characteristics of Subjects
Table 1
 
Characteristics of Subjects
Controls Mild Glaucoma Moderate Glaucoma Severe Glaucoma P Value
Number 293 313 48 26
Age 67.6 ± 11.1 64.8 ± 10.5 68.2 ± 11.8 67.3 ± 11.0 0.007*
Sex, M/F 113/180 133/180 26/22 6/20 <0.001†
BMI 22.5 ± 3.2 22.4 ± 3.1 22.5 ± 3.0 22.0 ± 2.3 0.89*
Alcohol drinker 118 (40.3%) 148 (47.3%) 22 (45.8%) 19 (73.1%) 0.009†
Current smoker 33 (11.3%) 35 (11.2%) 8 (16.7%) 6 (23.1%) 0.23†
Total comorbid illnesses
 0 228 (77.8%) 256 (81.8%) 33 (68.8%) 20 (76.9%) 0.36*
 1 61 (20.8%) 52 (16.6%) 13 (27.1%) 5 (19.2%)
 2 or more 4 (1.4%) 5 (1.6%) 2 (4.2%) 1 (3.8%)
Walking time per day, min 83.7 ± 90.9 83.0 ± 93.4 76.0 ± 73.4 67.9 ± 69.0 0.80*
History of falls 50 (17.1%) 50 (16.0%) 12 (25.0%) 2 (7.7%) 0.26†
BCVA in the better eye, LogMAR 0.01 ± 0.03 0.01 ± 0.02 0.01 ± 0.03 0.01 ± 0.03 0.21*
BCVA in the worse eye, LogMAR 0.02 ± 0.04 0.02 ± 0.04 0.03 ± 0.04 0.02 ± 0.04 0.74*
MD in the better eye, dB −1.4 ± 1.8 −8.0 ± 1.9 −16.9 ± 4.5 <0.001*
MD in the worse eye, dB −6.0 ± 5.7 −14.1 ± 5.2 −21.0 ± 4.9 <0.001*
use of topical Beta blockers 141 (45.0%) 19 (39.6%) 18 (69.2%) 0.04†
Table 2
 
Number of Subjects by Group With Fear of Falling
Table 2
 
Number of Subjects by Group With Fear of Falling
Controls Mild Glaucoma Moderate Glaucoma Severe Glaucoma P Value
Prevalence of fear of falling 35/293 = 11.9% 38/313 = 12.1% 12/48 = 25.0% 6/26 = 23.1% 0.035*; 0.028†
Table 3
 
Risk Factors for Fear of Falling in Subjects With or Without Glaucoma: Crude and Multivariable Adjusted Results
Table 3
 
Risk Factors for Fear of Falling in Subjects With or Without Glaucoma: Crude and Multivariable Adjusted Results
Crude Age- and Sex-Adjusted Multivariable Adjusted
Mild glaucoma in the better eye (ref control) 1.02 (0.62–1.66) 1.47 (0.84–2.48) 1.44 (0.83–2.51)
Moderate glaucoma in the better eye (ref control) 2.46 (1.17–5.16) 2.51 (1.14–5.55) 2.33 (1.00–5.44)
Severe glaucoma in the better eye (ref control) 2.21 (0.83–5.88) 3.04 (1.06–8.69) 4.06 (1.39–11.90)
BCVA in the better eye (LogMAR per 0.1 increment) 2.61 (1.30–5.23) 1.50 (0.72–3.14)
BCVA in the worse eye (LogMAR per 0.1 increment) 2.12 (1.40–3.21) 1.58 (1.02–2.46)
Age (per 1 y) 1.08 (1.05–1.11) * 1.08 (1.05–1.11)
Female sex (male as ref) 1.66 (1.06–2.61) * 1.87 (1.11–3.13)
BMI, kg/m2 0.99 (0.92–1.06) 1.01 (0.93–1.09)
Presence of hypertension 1.06 (0.67–1.69) 0.78 (0.48–1.26)
Presence of diabetes mellitus 1.11 (0.58–2.14) 1.16 (0.59–2.31)
Presence of cerebral infarction 2.48 (0.65–9.51) 2.53 (0.63–10.09) *
Presence of depression 2.80 (0.96–8.13) 3.61 (1.15–11.3)
Presence of comorbid illnesses (yes or no) 2.48 (1.54–3.98) 2.28 (1.39–3.73) 2.03 (1.20–3.43)
Use of topical beta blockers 1.02 (0.58–1.80) 1.15 (0.64–2.07) *
Use of antihypertensives 1.22 (0.77–1.95) 0.91 (0.56–1.48) *
Use of sleeping aids 1.74 (0.73–4.11) 1.15 (0.47–2.83) *
Current smoker (never or former as ref) 0.44 (0.44–1.79) 1.19 (0.56–2.53)
Alcohol drinker (non-drinker as ref) 0.62 (0.39–0.98) 0.97 (0.57–1.67)
History of falls 6.16 (3.81–9.95) 5.39 (3.23–8.91) 5.22 (3.11–8.75)
Table 4
 
Risk Factors for Fear of Falling: Crude and Multivariable Adjusted Results in Subjects With Glaucoma
Table 4
 
Risk Factors for Fear of Falling: Crude and Multivariable Adjusted Results in Subjects With Glaucoma
Crude Age- and Sex-Adjusted Multivariable Adjusted
MD in the better eye (per 1-dB increment) 0.93 (0.89–0.98) 0.94 (0.89–0.99) 0.93 (0.88–0.99)
MD in the worse eye (per 1-dB increment) 0.96 (0.93–1.00) 0.97 (0.93–1.01) *
BCVA in the better eye (LogMAR per 0.1 increment) 5.69 (1.97–16.52) 3.07 (0.98–9.63)
BCVA in the worse eye (LogMAR per 0.1 increment) 2.83 (1.67–4.80) 2.19 (1.25–3.84)
Age (per 1 y) 1.08 (1.04–1.11) * 1.06 (1.03–1.10)
Female sex (male as ref) 1.68 (0.95–2.97) *
BMI, kg/m2 0.97 (0.88–1.07) 0.98 (0.89–1.09)
Presence of hypertension 0.73 (0.38–1.40) 0.55 (0.28–1.08)
Presence of diabetes mellitus 1.35 (0.64–2.87) 1.18 (0.54–2.61)
Presence of cerebral infarction 1.50 (0.31–7.25) 1.43 (0.29–7.16) *
Presence of depression 6.31 (1.53–26.00) 6.85 (1.46–32.19) 7.18 (1.58–32.53)
Presence of comorbid illness (yes or no) 2.57 (1.39–4.75) 2.31 (1.21–4.41)
Use of topical beta blockers 1.02 (0.58–1.80) 1.15 (0.64–2.07) *
Use of antihypertensives 0.89 (0.47–1.68) 0.65 (0.34–1.27) *
Use of sleeping aids 2.25 (0.69–7.32) 1.69 (0.48–5.95) *
Current smoker (never or former as ref) 0.99 (0.42–2.32) 1.45 (0.58–3.60) *
Alcohol drinker (non-drinker as ref) 0.82 (0.46–1.44) 1.22 (0.65–2.31) *
History of falls 4.95 (2.65–9.24) 3.96 (2.06–7.62) 4.28 (2.20–8.34)
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