Vision and Falls inOlder People: RiskFactors andInterventionStrategies

Stephen R. Lord, PhD, DSc*, Stuart T. Smith, PhD,Jasmine C. Menant, PhD

KEYWORDS

� Accidental falls � Aged � Balance � Fractures � Vision

VISION, BALANCE, AND GAIT

Accurate control of posture, balance, and locomotion through the environmentinvolves a coordinated set of sensorimotor processes that continually encode andcompare information from visual, vestibular, proprioceptive, and sensorimotor feed-back and cognitive sources. The extent to which visual information dominates thisprocess is best demonstrated when people stand with their eyes closed; posturalsway increases by between 20% and 70%.1–3 Similarly, the compelling illusion ofself-motion (vection) generated in the stationary participant by visual motion stimulithat cover a large area of the visual field4 and the coupling of postural sway with visualmotion observed with the “moving room” paradigm5,6 confirm the significant roleplayed by visual information in the perception and control of balance. For example,while seated on a stationary train at a platform, if an adjacent train at the platformbegins to move away, individuals often experience a transient sense that they them-selves are moving. The visual motion of the adjacent train is interpreted as self-motionby the observer.Older adults, particularly those at risk of falls, tend to sway more in response to

large-field, sinusoidally oscillating, visual motion stimuli than younger or healthy olderadults.7,8 Whereas younger and healthy older adults can adapt to the conflict between(moving) visual and (static) proprioceptive, somatosensory, and vestibular sensorycues during moving room stimuli, older adults, particularly those who are fall prone,generally take longer to do so.9 Furthermore, in conditions in which the spatiotemporal

Falls and Balance Research Group, Neuroscience Research Australia, University of New SouthWales, Barker Street, Randwick, Sydney, NSW 2031, Australia* Corresponding author.E-mail address: s.lord@neura.edu.au

Clin Geriatr Med 26 (2010) 569–581doi:10.1016/j.cger.2010.06.002 geriatric.theclinics.com0749-0690/10/$ – see front matter � 2010 Elsevier Inc. All rights reserved.

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characteristics of the visual motion are rapidly changed, the magnitude of head swayvelocity in older adults increases significantly but remains unchanged in youngeradults.10 Postural responses observed in moving room experiments have been inter-preted to reflect a preferential weighting of visual information for the control of posturein older adults, particularly those who are prone to falling,11 likely because of attenu-ation of the compensatory mechanisms of proprioception and the vestibular system.Recent theoretical models12 of sensory integration by the central nervous system

propose that inherently “noisy” information from different sensory modalities aredynamically reweighted such that whenever the quality of sensory signal from oneor more systems is degraded (via age-related declines in peripheral transduction orcentral processing of sensory information), the most reliable sensory information avail-able weights most significantly in neural computations. In the case of posture control,each sensory modality provides an estimate of the orientation and movement of thebody in space. These estimates are then used by the central nervous system mecha-nisms to compute the appropriate postural control strategies to maintain balance.13

Jeka and colleagues14 have suggested that the increased weighting of visual overproprioceptive and vestibular information may be more influential during transientchanges in visual stimulation. Once a postural response to transient changes in thevisual scene is initiated, the time to reacquire postural stability may depend on integra-tion by the central nervous system of posture-related cues from the proprioceptiveand vestibular systems.15 Any deficit or delay in the processing of transient or movingvisual information may therefore increase the risk of postural instability and falls.Despite many reports in the literature illustrating the effect of the moving room on

balance control, only a few studies have systematically investigated the sensitivityof the human central nervous system to visual motion as a function of age. Perceptionof visual movement is generally considered to initially involve neural processes in thevisual cortex,16 and an extensive body of research has developed the understandingof the neurophysiologic mechanisms involved (for review see article by Grill-Spectorand Malach17). Several behavioral studies have reported age-related increases inthe ability to detect and discriminate visual motion in linear (left-right/up-down)flow,18–20 and deficits in the perception of linear visual motion processing have alsobeen related to impaired static postural stability. In a population-based cohort studyof more than 1500 individuals, Freeman and colleagues21 have shown that individualswith poorer motion detection thresholds were more likely to be unsuccessful intandem stand (odds ratio [OR], 1.56; 95% confidence interval [CI], 1.13–2.15) andstanding on one foot (OR, 3.08; 95% CI, 1.57–6.06). There is some evidence thatage-related decline in visual motion sensitivity may be more pronounced for linearmotion than for radial motion.22,23 Radial visual motion, or optic flow,24 occurs whenan observer moves forward (or backward) through the world. If older adults areimpaired in their ability to correctly encode the visual flow cues coincident with self-motion through the environment, they may be unable to generate appropriate visuallyguided motor responses.With advances in virtual reality technology, whereby the real body movements of an

individual can be recorded and used to update (in real time) a representation of thosemovements within a computer-generated environment, it has recently becomepossible to measure manipulations of the kinds of visual optic flow stimuli that occurnaturally during normal self-motion through the environment.9 Using a virtual hallwaycomposed of 2 sidewalls of white random dots on a black background, presented viaa head-mounted display, Chou and colleagues25 demonstrated that older adultsrespond to changes in the flow speed and the asymmetry (left or rightwallmoving fasterthan other) of the virtual hallway in the same way as younger adults. Whereas the

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walking speed of older adults was generally slower than that of the younger adults (andstride frequency higher), the effect of systematic changes in the flow speed of the walldotswas nodifferent in the younger andolder participants. In contrast to these findings,Berard and colleagues26 have reported impairments in the ability of older adults to useoptic flow information to control the direction of locomotion (heading) in a virtual realitytask. During a static postural task, Haibach and colleagues27 have presented datashowing that in response to an optic flow stimulus, although the postural response ofolder adults was greater than that of younger adults, the older adults’ perception ofself-motion (vection) was diminished. Although virtual reality technology offers a noveltechnique for investigating the role of visual control of postural stability and gait in anincreasingly ecologically validway, further studies are required to resolvewhether olderand younger adults are differentially affected by optic flow stimuli.Impaired visual motion processing might also decrease the chance of generating

visuomotor responses that are appropriate for avoiding or negotiating obstaclesthat enter one’s visual field, such as when an animal runs toward you or when youencounter a step while walking. Obstacle avoidance becomes increasingly impairedwith age.28 Safe and effective navigation of complex environments relies on purpose-ful acquisition of visual information to identify obstacles and targets, and severalstudies (eg, the study by Hollands and Marple-Horvat29) have shown that individualsdirect their gaze toward stepping targets before executing steps toward those targets.When walking toward floor-based targets, older adults tend to generate eye move-ments toward, and then spend greater time looking at, a target location whencompared with younger adults.30 Older adults who are at higher risk for falling alsotend to look away from the target significantly sooner than low-risk adults and exhibitgreater mediolateral foot placement variability.31 One hypothesis to account for thepremature shift of gaze in high-risk older adults suggests that they may be implicitlyaware of their impaired visual processing and, as a consequence, adopt a strategyto maximize the amount of time that they spend in acquiring and storing visuospatialinformation about the environment to plan subsequent stepping movements.32 Scoviland colleagues33 argue that the acquisition and storage of visuospatial informationconcerning the surrounding environment is critical for generating corrective steppingin response to unpredictable or unexpected balance perturbations and that anyimpairment in the acquisition or processing of visual information would affect theability to use stored and real-time visual information to guide stepping reactions.Chapman and Hollands32 argue that training older adults at high risk of falls to delaylooking away from a target until after heel contact may lead to an improvement in voli-tional stepping performance, an argument supported by recent research showing thatvisual feedback training in older women can improve online visuomotor processing forpostural adjustments to avoid moving obstacles.34

Several studies have investigated the effects of visual impairments on posturalsway,35–39 gait biomechanics when stepping up40–42 or down a single step,43,44 orwalking at a natural pace along a simple walkway.45 These studies have shown thatincreased binocular refractive blur35,37,38 and simulated cataracts36 lead to increasedpostural sway in younger and older people, with a greater effect when somatosen-sory38 or vestibular information is disrupted35–37 or when secondary physical orcognitive tasks are performed.37 In addition, when vision is impaired by the use oflight-scattering glasses, older people adopt a slower and more cautious steppingup and down strategy. To compensate for the visual impairment and to maintaindynamic stability while preventing tripping, older people displayed more cautiousreactions while stepping onto a raised surface for single step up40 or while steppingonto a raised surface during a normal gait cycle.42 When stepping down, despite

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placing more body weight on the contralateral limb and increasing ankle plantarflexion and knee flexion,44 older people seem to exhibit poorer mediolateral stabilityfor single-leg stance in the impaired versus optimal vision condition.43 Greaterpostural instability during the phase of gait when all weight is carried by 1 leg(single-leg stance) increases the risk of falling. Finally, compared with young adultsin similar blurred visual conditions, when stepping up, older people spent 20% longerin the double-support phase and showed reduced mediolateral center of mass-centerof pressure divergence but no difference in toe clearance.41 Age-related decline inlateral balance control46 likely explains why older people would perceive mediolateralinstability as a greater threat to falling than tripping and would adapt their steppingpatterns accordingly.In the preceding section, the authors have reviewed the literature showing that there

are systematic changes in the ability of older adults to use dynamic (motion) and staticvisual information. Furthermore, the results of laboratory-based experimental studieshave shown that degradation in visual information processing is related to impair-ments in gait and posture. In the following sections, the authors outline some of theclinical evidence relating visual impairment and falls in older adults.

VISION, FALLS, AND FRACTURES

Prospective studies of the risk of falls using tests of visual acuity, edge-contrast sensi-tivity, stereopsis or depth perception, and visual field loss have included visual impair-ment as a possible risk factor. Although there have been some inconsistencies,research findings generally indicate that reductions in each of these visual measuresincrease the risk of falls in older people. Impaired distance visual acuity, that is, poorfine-detail vision, has been identified as a risk factor for falls in people living in assistedcare accommodation47 and independently in the community.48–51 It has also beenreported that poor visual acuity increases risk of falls when coupled with balanceimpairment or with both balance and hearing impairments.52 However, other studieshave failed to find an association between visual acuity and falls, especially whenadjusting for age.1,53–59 Reduced visual acuity has also been identified to be an inde-pendent predictor of fall-related hip fracture in a large case-control study59 and 2 of 3prospective studies.60–62 Although probably not the most precise visual measure forassessing the risk of fall and fracture, this readily available test seems to be a usefulvisual screening measure for assessing risk of fall.Edge-contrast sensitivity assesses the ability to detect edges of variable orientation

under progressively reducing contrast conditions and may thus replicate the ability todetect ground-level hazards, such as steps, kerbs, and pavement cracks andmisalignments, over which older people are likely to trip. Several studies have foundthat poor edge-contrast sensitivity significantly increased the risk of falls in olderpeople living in assisted care accommodation1 and in community dwellers,63,64

more so than poor visual acuity or reduced visual field size,48 as well as the risk ofmultiple falls and fractures.65 However, 2 other recent studies have reported thatcontrast sensitivity was not a predictor of falls after adjusting for age and other con-founding factors such as cognition.55,56

Depth perception or stereopsis evaluates the ability to judge distances accuratelyand perceive spatial relationships and is thus important for negotiating and avoidingobstacles and hazards in the environment. With the exception of only one study,56

poor depth perception has been shown to increase the risk of multiple falls51,63 andhip fractures.59,62 Lord and Dayhew63 also reported that older people with good visionin both eyes had a low rate of falls, whereas those with good vision in one eye but only

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moderate or poor vision in the other had elevated rates of falls, equivalent to those withmoderate or poor vision in both eyes. Similarly, Felson and colleagues61 found thatolder people who had good vision in one eye, but only moderately good vision inthe other, had an elevated risk of hip fracture.Early studies on risk of falls that included visual field loss as a possible predictor

found little association between this measure and falls. In a large prospective study,Nevitt and colleagues51 found that visual field loss did not increase the risk of recurrentfalls, and Glynn and colleagues66 found that visual field loss was only weakly associ-ated with falls in patients attending a glaucoma clinic. However, more recent studieshave suggested that visual field loss is an important risk factor for falls,48 multiplefalls,49,55 and fractures49 and that such risk remains when adjusting for demographicand health variables.55,56

Finally, there is evidence that older people with poor vision as a result of eye diseaseare at high risk of falls. Compared with healthy older adults, those suffering from age-related macular degeneration (AMD) had a greater risk of falls as indicated by theirhigh composite fall risk score, which combined poor performance in tests of edge-contrast sensitivity, visual reaction time, and balance.67 These findings wereconfirmed in a subsequent prospective investigation on falls wherein older peoplewith AMD experienced on average more than twice as many injurious falls as theirhealthy counterparts (0.37 vs 0.16 injurious falls per person-year) and the age-adjusted incidence rate ratio (IRR) for injurious falls for older people with AMDcompared with those without AMD was 1.77 (95% CI, 1.07–3.20).68

In the Blue Mountains Eye Study, which involved 3299 people older than 49 years,the presence of cataracts and the use of nonmiotic glaucoma medication were signif-icantly associated with 2 or more falls in the previous 12 months.48 Having glaucomaalso significantly increased the risk of retrospective falls by more than 4-fold, afteradjusting for visual acuity in 3280 older Malay people aged 40 to 80 years (meanage, 58.7 � 11 years).69 However, according to 2 large case-control59 and prospec-tive62 studies, neither cataracts59,62 nor self-reported glaucoma59 was associatedwith increased risk of fractures. These inconsistent findings may relate to imprecisionin diagnosis of eye disease or variable visual functioning for those with eye disease.Nevertheless, these findings suggest that the prevention and treatment of commoneye diseases in older people could help prevent falls in this population (see sectionon visual interventions for preventing falls).

INAPPROPRIATE GLASSES

Many older people who wear glasses with outdated prescriptions or who wear noglasses at all may benefit from wearing new glasses with correct prescriptions,70–72

indicating that older people are not aware of their declining vision and/or do notperceive the benefits of regular vision assessments and that updated glassesoutweigh risks to safety and lifestyle. Reduced access to eye care may also constitutean important barrier for some frail older people.Elliott and Chapman73 demonstrated that spectacle lens magnification affects step

negotiation in older people. The investigators found that compared with lenses withoptimal refractive correction, lenses with a positive blur (1 and 2 diopter [D]) led toa longer step and increased vertical toe clearance, suggesting that the step appearedto be larger and closer to the feet. Opposite gait adaptations were observed when theparticipants wore lenses with a negative blur (�1 and �2 D), suggesting that the stepappeared farther away. These findings have significant implications with respect togait and risk of falls in older people in relation to providing large changes in lens

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prescriptions in updated spectacles and after cataract surgery (see section on visualinterventions for preventing falls).Irrespective of the correction for distance vision, multifocal (bifocal, trifocal, or

progressive lenses) glasses may also pose a significant risk of falling for older people.These glasses have benefits for activities that require changes in focal length,including everyday tasks of driving, shopping, and cooking. However, multifocalglasses may predispose older people to falls because viewing the environmentthrough their lower lenses impairs the important visual capabilities (contrast sensitivityand depth perception) for detecting environmental hazards, particularly in unfamiliarenvironments. When walking, people view the environment at distances approxi-mating 2 steps ahead.74 For multifocal wearers, the lower lenses of their glasses(with focal lengths of 0.6 m) blur their lower visual fields, impairing vision at the criticalfocal distances required for detecting and discriminating floor-level objects (approxi-mately 1.5–2 m).Johnson and colleagues75,76 have investigated in older people the effects of

wearing single-lens glasses versus multifocal-lens glasses (progressive and bifocallenses) on the biomechanics of step negotiation and accuracy of foot placementwhen stepping onto a step. In these studies, when wearing multifocal glasses, olderpeople displayed more variability in vertical toe clearance when stepping up76 andin foot placement when negotiating the step.75 Contacts with the edge of the step(12 of 875 trials)75 and trips76 occurred only when the participants wore multifocalglasses.76

Multifocal glasses also impair the ability of older people to negotiate multiple obsta-cles, particularly in situations in which attention is divided. Menant and colleagues77

asked 30 older multifocal glasses wearers to negotiate an obstacle course andcompared obstacle contact rates between trialswhere theparticipantswore theirmulti-focal glasseswith trialswhere theywore single lensdistanceglasses. In half the trials, asa secondary task, the participants were also required to read a series of letters pre-sented in front of them at eye level. In the dual-task trials, the participants contactedsignificantly more obstacles when wearing multifocal glasses. Measurement of eyeand head positioning suggested that this impaired performance was likely caused bya failure to adopt a compensatory increase in pitch headmovement, resulting in blurredvision of obstacles viewed through the lower segments of multifocal glasses.Lord and Dayhew78 also examined the effects of multifocal glasses on vision and

falls in older people. In a prospective cohort study of 156 participants aged 63 to 90years, 56% were regular wearers of multifocal glasses. These participants performedsignificantly worse in distant depth perception and edge-contrast sensitivity tests inconditions that forced them to view test stimuli through the lower segments of theirglasses. Those who wore multifocal glasses had significantly greater odds of fallingin the 1-year follow-up period than those who wore non-multifocal glasses (OR,2.27; 95% CI, 1.04–4.97), when adjusting for age and known physiologic risk factorsfor falls. Participants who wore multifocal glasses were also more likely to fall whenoutside their homes (OR, 2.54; 95% CI, 1.19–5.77) and when walking up or downthe stairs.

VISUAL INTERVENTIONS FOR PREVENTING FALLS

Two related trials have examined the effects of expedited cataract surgery in reducingfall rates. The first study involving 306 women 70 years and older examined the effi-cacy of cataract surgery on the first eye.79 Participants were randomized to eitherexpedited (approximately 4 weeks) or routine (12 months’ wait) surgery. Vision, visual

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disability, levels of physical activity, anxiety, depression, and balance confidenceimproved significantly in the operated group at the 6-month retest and during the12 months of follow-up; the fall rate in the operated group was reduced by 34%compared with the controls (IRR, 0.66; 95% CI, 0.45–0.96). Although the number ofcases was few, 4 participants in the operated group (3%) and 12 (8%) in the controlgroup, this trial also demonstrated that a fall prevention intervention can be effectivein reducing fractures (P 5 .04).A follow-on study by the same group determined if cataract surgery of the second

eye leads to a further reduction in the number of falls, as well as measured the asso-ciated health gain.80 In the study, 239 women older than 70 years with 1 unoperatedcataract who had been referred to a hospital ophthalmology department wererandomized to either expedited (approximately 4 weeks) or routine (12 months’ wait)surgery. Visual function (especially stereopsis), confidence, visual disability, and hand-icap improved in the operated group compared with the control group. During 12months’ follow-up, the rate of falling was reduced by 32% in the operated group(IRR, 0.68; 95% CI, 0.39–1.19). Although the reduction in the number of falls wassimilar to that in the previous study on cataract surgery for the first eye, the findingswere not significant and there was no clear pattern of reduction in fall rate, apartfrom very high fall rates being present in 3 participants in the control group. The studyalso had reduced power, resulting from an inability to recruit participants as a result ofwaiting times decreasing from greater than 1 year to less than 6 months in the periodthe study was performed. Therefore, it can be concluded that cataract surgery of thesecond eye improves visual disability and general health status, but the effect on rateof falling is uncertain.Two randomized controlled trials have evaluated the efficacy of visual assessment

and provision of new glasses as a primary basis of a visual intervention to prevent falls.The first trial involved 1090 participants 70 years and older and used a factorial designto assess the independent and combined effects of interventions aimed at visionimprovement, home hazard reduction, and group exercise.81 The visual improvementintervention comprised a referral to the participant’s usual eye care provider if theparticipant had impaired vision (poor visual acuity, decreased stereopsis, and/orreduced field of view) and was not already receiving treatment for this problem. Theeye care provider was also given the screening assessment results. Those partici-pants randomized to the visual intervention had a 4.4% reduction in the rate of fallsover 1 year (rate ratio [RR] for time to first fall, 0.89; 95% CI, 0.75–1.04), but this resultdid not reach statistical significance.The second trial82 was conducted in a group of 616 older community dwellers 70

years and older who were randomized to either an intervention group (n 5 309) ora control group (n 5 307) and were prospectively followed up for falls and fracturesfor 12 months. In the intervention group, 44% received vision-related treatments,most often a new pair of glasses (n 5 92). During the follow-up period, participantsfrom the intervention group reported significantly more falls than those from thecontrol group (RR, 1.57; 95% CI, 1.20–2.95). There was also a trend for more fall-related fractures in the intervention group (RR, 1.74; 95% CI, 0.97–3.11). The investi-gators concluded that the intervention participants might have required more time toadapt to their new glasses, often with significantly altered prescriptions,73 or that theyadopted more risk-taking activities (thus increasing the exposure to falls) after theirvision improvement.One recent intervention aimed to limit the use of multifocal glasses rather than

simply update glasses to a correct prescription.83,84 This randomized controlled trial,involving 606 older people and 13 months’ follow-up, assessed whether the provision

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of single-lens distance glasses to older participants who wore multifocal glassesreduces the incidence of falls. The intervention was aimed at older participants whowore multifocal glasses who were at increased risk of falls (fell in the past year orhad a Timed Up and Go test time >15 seconds). Because multifocal glasses havebenefits for activities that require changes in focal length, including everyday tasksof driving, shopping, and cooking, wearing single-lens glasses was recommendedprimarily for walking and outdoor activities. Overall, the intervention resulted in an8% reduction in all falls (IRR, 0.92; 95% CI, 0.73–1.16). The intervention was effectivein preventing falls in people who undertook outside activities more regularly. In thisgroup, there were significant reductions in all falls (IRR, 0.60; 95% CI, 0.43–0.85), fallsoutside the home (IRR, 0.61; 95%CI, 0.42–0.87), and injurious falls (IRR, 0.62; 95%CI,0.42–0.92). However, in the intervention group, there was a significant increase in fallsoutside home in people who undertook little outdoor activity (IRR, 1.56; 95% CI, 1.11–2.19). These findings suggest that, with appropriate counseling, compliance with theintervention was acceptable and that the provision of single-lens glasses for olderpeople who wore multifocal glasses and part in regular outdoor activities can be aneffective fall prevention strategy. However, the intervention may be harmful for thosewho wore multifocal glasses and had low levels of outdoor activity.One randomized control trial has demonstrated that older people with severe visual

impairment can benefit from a targeted home safety assessment and modificationintervention program.85,86 In this study, 391 community-dwelling older people 75years and older and suffering from visual impairment were assigned to eithera home safety program (n 5 100), an exercise program with vitamin D supplementa-tion (n 5 97), both the home safety and the exercise program (n 5 98), or a social visitcontrol group (n 5 96). Falls were reduced by 41% in the older people randomized tothe home safety program treatment arms (IRR, 0.59; 95% CI, 0.42–0.93).85 Not onlyhazard-related falls (IRR, 0.40; 95% CI, 0.21–0.74) but also non–hazard-related falls(IRR, 0.43; 95% CI, 0.21–0.90) were significantly reduced in the home safety programgroup (n 5 100) compared with the social visit group (n 5 96).86 According to theinvestigators, the success of this intervention could be attributed to (1) the effective-ness of the removal and modification of the home hazards (for hazard-related falls),(2) the increased awareness of the older participants regarding home hazards negoti-ation after the individual advice delivered by a trained professional, and (3) the poten-tial increased fear of falling after the occupational therapist’s intervention leading toactivity restriction and, in turn, reduced exposure to risk.86

SUMMARY

Vision makes an important contribution to balance, and impaired vision resulting fromeye disease is a significant independent risk factor for falls and fractures in olderpeople. Reduced ability to detect low-contrast hazards, judge distances, perceivespatial relationships, and process moving visual information all seem to be the majorvisual risk factors for falls. Multifocal glasses can add to the risk of falls because theirnear-vision lenses impair distance-contrast sensitivity and depth perception in thelower visual field, reducing the ability of an older person to detect environmentalhazards. There is now evidence from randomized controlled trials that maximizingvision through restricting the use of multifocal glasses to active older people and cata-ract surgery for the first eye are effective fall prevention strategies. Occupationaltherapy interventions involving home hazard reductions are also effective in prevent-ing falls in severely visually impaired older people. Although interventions involvingvision assessment and provision of new spectacles improve performance in visual

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tests in community-dwelling older people, such interventions have not been shown toreduce the risk of falls. Public health initiatives are required to raise awareness in olderpeople and their carers of the importance of regular eye examinations and the use ofappropriate prescription glasses.

REFERENCES

1. Lord SR, Clark RD, Webster IW. Postural stability and associated physiologicalfactors in a population of aged persons. J Gerontol 1991;46(3):M69–76.

2. Magnusson M, Enbom H, Johansson R, et al. Significance of pressor input fromthe human feet in anterior-posterior postural control. The effect of hypothermia onvibration-induced body-sway. Acta Otolaryngol 1990;110(3–4):182–8.

3. Paulus WM, Straube A, Brandt T. Visual stabilization of posture. Physiologicalstimulus characteristics and clinical aspects. Brain 1984;107:1143–63.

4. Berthoz A, Pavard B, Young LR. Perception of linear horizontal self-motioninduced by peripheral vision (linear vection) basic characteristics and visual-vestibular interactions. Exp Brain Res 1975;23(5):471–89.

5. Kelly JW, Riecke B, Loomis JM, et al. Visual control of posture in real and virtualenvironments. Percept Psychophys 2008;70(1):158–65.

6. Lee DN, Lishman JR. Visual proprioceptive control of stance. J Hum Mov Stud1975;1:87–95.

7. Simoneau M, Teasdale N, Bourdin C, et al. Aging and postural control: posturalperturbations caused by changing the visual anchor. J Am Geriatr Soc 1999;47(2):235–40.

8. Sundermier L, Woollacott MH, Jensen JL, et al. Postural sensitivity to visual flow inaging adults with and without balance problems. J Gerontol A Biol Sci Med Sci1996;51(2):M45–52.

9. Haibach PS, Slobounov SM, Newell KM, et al. The potential applications ofa virtual moving environment for assessing falls in elderly adults. Gait Posture2008;27(2):303–8.

10. O’Connor KW, Loughlin PJ, Redfern MS, et al. Postural adaptations to repeatedoptic flow stimulation in older adults. Gait Posture 2008;28(3):385–91.

11. Wade MG, Lindquist R, Taylor JR, et al. Optical flow, spatial orientation, and thecontrol of posture in the elderly. J Gerontol B Psychol Sci Soc Sci 1995;50(1):P51–8.

12. Knill DC, Pouget A, Knill DC, et al. The Bayesian brain: the role of uncertainty inneural coding and computation. Trends Neurosci 2004;27(12):712–9.

13. Peterka RJ. Sensorimotor integration in human postural control. J Neurophysiol2002;88(3):1097–118.

14. Jeka J, Allison L, Saffer M, et al. Sensory reweighting with translational visualstimuli in young and elderly adults: the role of state-dependent noise. Exp BrainRes 2006;174(3):517–27.

15. Haibach PS, Slobounov SM, Slobounova ES, et al. Aging and time-to-posturalstability following a visual perturbation. Aging Clin Exp Res 2007;19(6):438–43.

16. Maunsell JH, Newsome WT. Visual processing in monkey extrastriate cortex.Annu Rev Neurosci 1987;10:363–401.

17. Grill-Spector K, Malach R. The human visual cortex. Annu Rev Neurosci 2004;27:649–77.

18. Gilmore GC, Wenk HE, Naylor LA, et al. Motion perception and aging. PsycholAging 1992;7(4):654–60.

Lord et al578

19. Snowden RJ, Kavanagh E, Snowden RJ, et al. Motion perception in the ageingvisual system: minimum motion, motion coherence, and speed discriminationthresholds. Perception 2006;35(1):9–24.

20. Tran DB, Silverman SE, Zimmerman K, et al. Age-related deterioration of motionperception and detection. Graefes Arch Clin Exp Ophthalmol 1998;236(4):269–73.

21. Freeman EE, Broman AT, Turano KA, et al. Motion-detection threshold andmeasures of balance in older adults: the SEE Project. Invest Ophthalmol VisSci 2008;49(12):5257–63.

22. Atchley P, Andersen GJ. The effect of age, retinal eccentricity, and speed on thedetection of optic flow components. Psychol Aging 1998;13(2):297–308.

23. Billino J, Bremmer F, Gegenfurtner KR, et al. Differential aging of motion process-ing mechanisms: evidence against general perceptual decline. Vision Res 2008;48(10):1254–61.

24. Gibson JJ. The perception of the visual world. Boston: Houghton Miffin; 1966.25. Chou YH, Wagenaar RC, Saltzman E, et al. Effects of optic flow speed and lateral

flow asymmetry on locomotion in younger and older adults: a virtual reality study.J Gerontol B Psychol Sci Soc Sci 2009;64(2):222–31.

26. Berard JR, Fung J, McFadyen BJ, et al. Aging affects the ability to use optic flowin the control of heading during locomotion. Exp Brain Res 2009;194(2):183–90.

27. Haibach P, Slobounov S, Newell K. Egomotion and vection in young and elderlyadults. Gerontology 2009;55(6):637–43.

28. Weerdesteyn V, Nienhuis B, Duysens J. Advancing age progressively affectsobstacle avoidance skills in the elderly. Hum Mov Sci 2005;24(5–6):865–80.

29. Hollands MA, Marple-Horvat DE. Coordination of eye and leg movements duringvisually guided stepping. J Mot Behav 2001;33(2):205–16.

30. Chapman GJ, Hollands MA. Evidence for a link between changes to gaze behav-iour and risk of falling in older adults during adaptive locomotion. Gait Posture2006;24(3):288–94.

31. Chapman GJ, Hollands MA. Age-related differences in visual samplingrequirements during adaptive locomotion. Exp Brain Res 2010;201(3):467–78.[Online].

32. Chapman GJ, Hollands MA. Evidence that older adult fallers prioritise the plan-ning of future stepping actions over the accurate execution of ongoing stepsduring complex locomotor tasks. Gait Posture 2007;26(1):59–67.

33. Scovil CY, Zettel JL, Maki BE, et al. Stepping to recover balance in complexenvironments: is online visual control of the foot motion necessary or sufficient?Neurosci Lett 2008;445(1):108–12.

34. Hatzitaki V, Voudouris D, Nikodelis T, et al. Visual feedback training improvespostural adjustments associated with moving obstacle avoidance in elderlywomen. Gait Posture 2009;29(2):296–9.

35. Anand V, Buckley J, Scally A, et al. The effect of refractive blur on posturalstability. Ophthalmic Physiol Opt 2002;22(6):528–34.

36. Anand V, Buckley JG, Scally A, et al. Postural stability changes in the elderly withcataract simulation and refractive blur. Invest Ophthalmol Vis Sci 2003;44(11):4670–5.

37. Anand V, Buckley JG, Scally A, et al. Postural stability in the elderly duringsensory perturbations and dual tasking: the influence of refractive blur. InvestOphthalmol Vis Sci 2003;44(7):2885–91.

38. Straube A, Paulus W, Brandt T. Influence of visual blur on object-motion detection,self-motion detection and postural balance. Behav Brain Res 1990;40(1):1–6.

Visual Risk Factors for Falls 579

39. Wood JM, Lacherez PF, Black AA, et al. Postural stability and gait among olderadults with age-related maculopathy. Invest Ophthalmol Vis Sci 2009;50(1):482–7.

40. Heasley K, Buckley JG, Scally A, et al. Stepping up to a new level: effects of blur-ring vision in the elderly. Invest Ophthalmol Vis Sci 2004;45(7):2122–8.

41. Heasley K, Buckley JG, Scally A, et al. Falls in older people: effects of age andblurring vision on the dynamics of stepping. Invest Ophthalmol Vis Sci 2005;46(10):3584–8.

42. Vale A, Buckley JG, Elliott DB, et al. Gait alterations negotiating a raised surfaceinduced by monocular blur. Optom Vis Sci 2008;85(12):1128–34.

43. Buckley JG, Heasley K, Scally A, et al. The effects of blurring vision on medio-lateral balance during stepping up or down to a new level in the elderly. GaitPosture 2005;22(2):146–53.

44. Buckley JG, Heasley KJ, Twigg P, et al. The effects of blurred vision on themechanics of landing during stepping down by the elderly. Gait Posture 2005;21(1):65–71.

45. Helbostad JL, Vereijken B, Hesseberg K, et al. Altered vision destabilizes gait inolder persons. Gait Posture 2009;30(2):233–8.

46. Mille ML, Johnson ME, Martinez KM, et al. Age-dependent differences in lateralbalance recovery through protective stepping. Clin Biomech 2005;20(6):607–16.

47. Tinetti ME, Williams TF, Mayewski R. Fall risk index for elderly patients based onnumber of chronic disabilities. Am J Med 1986;80(3):429–34.

48. Ivers RQ, Cumming RG, Mitchell P, et al. Visual impairment and falls in olderadults: the Blue Mountains Eye Study. J Am Geriatr Soc 1998;46(1):58–64.

49. Klein BE, Moss SE, Klein R, et al. Associations of visual function with physicaloutcomes and limitations 5 years later in an older population: the Beaver DamEye Study. Ophthalmology 2003;110(4):644–50.

50. Lord SR, Menz HB. Visual contributions to postural stability in older adults. Geron-tology 2000;46(6):306–10.

51. Nevitt MC, Cummings SR, Kidd S, et al. Risk factors for recurrent nonsyncopalfalls. A prospective study. JAMA 1989;261(18):2663–8.

52. Kulmala J, Viljanen A, Sipila S, et al. Poor vision accompanied with other sensoryimpairments as a predictor of falls in older women. Age Ageing 2009;38(2):162–7.

53. Brocklehurst JC, Robertson D, James-Groom P. Clinical correlates of sway in oldage–sensory modalities. Age Ageing 1982;11(1):1–10.

54. Campbell AJ, Borrie MJ, Spears GF. Risk-factors for falls in a community-based prospective-study of people 70 years and older. J Gerontol 1989;44(4):M112–7.

55. Coleman AL, Cummings SR, Yu F, et al. Binocular visual-field loss increases therisk of future falls in older white women. J Am Geriatr Soc 2007;55(3):357–64.

56. Freeman EE, Munoz B, Rubin G, et al. Visual field loss increases the risk of falls inolder adults: the Salisbury Eye Evaluation. Invest Ophthalmol Vis Sci 2007;48(10):4445–50.

57. Robbins AS, Rubenstein LZ, Josephson KR, et al. Predictors of falls amongelderly people. Results of two population-based studies. Arch Intern Med 1989;149(7):1628–33.

58. Tinetti ME, Speechley M, Ginter SF. Risk factors for falls among elderly personsliving in the community. N Engl J Med 1988;319(26):1701–7.

59. Ivers RQ, Norton R, Cumming RG, et al. Visual impairment and risk of hip fracture.Am J Epidemiol 2000;152(7):633–9.

Lord et al580

60. Dargent-Molina P, Favier F, Grandjean H, et al. Fall-related factors and risk of hipfracture: the EPIDOS prospective study. Lancet 1996;348(9021):145–9.

61. Felson DT, Anderson JJ, Hannan MT, et al. Impaired vision and hip fracture. TheFramingham Study. J Am Geriatr Soc 1989;37(6):495–500.

62. Cummings SR, Nevitt MC, Browner WS, et al. Risk factors for hip fracture in whitewomen. Study of Osteoporotic Fractures Research Group. N Engl J Med 1995;332(12):767–73.

63. Lord SR, Dayhew J. Visual risk factors for falls in older people. J Am Geriatr Soc2001;49(5):508–15.

64. Lord SR, Ward JA. Age-associated differences in sensori-motor function andbalance in community dwelling women. Age Ageing 1994;23(6):452–60.

65. de Boer MR, Pluijm SM, Lips P, et al. Different aspects of visual impairment as riskfactors for falls and fractures in older men and women. J Bone Miner Res 2004;19(9):1539–47.

66. Glynn RJ, Seddon JM, Krug JH Jr, et al. Falls in elderly patients with glaucoma.Arch Ophthalmol 1991;109(2):205–10.

67. Szabo SM, Janssen PA, Khan K, et al. Older women with age-related maculardegeneration have a greater risk of falls: a physiological profile assessmentstudy. J Am Geriatr Soc 2008;56(5):800–7.

68. Szabo SM, Janssen PA, Khan K, et al. Neovascular AMD: an overlooked riskfactor for injurious falls. Osteoporos Int 2010;21(5):855–62. [Online].

69. LamoureuxEL,ChongE,WangJJ,et al. Visual impairment, causesofvision loss, andfalls: the Singapore Malay Eye Study. Invest Ophthalmol Vis Sci 2008;49(2):528–33.

70. Attebo K, Ivers RQ, Mitchell P. Refractive errors in an older population: the BlueMountains Eye Study. Ophthalmology 1999;106(6):1066–72.

71. Jack CI, Smith T, Neoh C, et al. Prevalence of low vision in elderly patientsadmitted to an acute geriatric unit in Liverpool: elderly people who fall aremore likely to have low vision. Gerontology 1995;41(5):280–5.

72. Tielsch JM, Sommer A, Witt K, et al. Blindness and visual impairment in an Amer-ican urban population. The Baltimore Eye Survey. Arch Ophthal 1990;108(2):286–90.

73. Elliott D, Chapman GJ. Adaptive gait changes due to spectacle magnificationand dioptric blur in older people. Invest Ophthalmol Vis Sci 2010;51(2):718–22.[Online].

74. Patla AE, Vickers JN. Where and when do we look as we approach and step overan obstacle in the travel path? Neuroreport 1997;8(17):3661–5.

75. Johnson L, Buckley JG, Harley C, et al. Use of single-vision eyeglasses improvesstepping precision and safety when elderly habitual multifocal wearers negotiatea raised surface. J Am Geriatr Soc 2008;56(1):178–80.

76. Johnson L, Buckley JG, Scally AJ, et al. Multifocal spectacles increase variabilityin toe clearance and risk of tripping in the elderly. Invest Ophthalmol Vis Sci 2007;48(4):1466–71.

77. Menant JC, St George RJ, Sandery B, et al. Older people contact more obstacleswhen wearing multifocal glasses and performing a secondary visual task. J AmGeriatr Soc 2009;57(10):1833–8.

78. Lord SR, Dayhew J, Howland A. Multifocal glasses impair edge-contrast sensi-tivity and depth perception and increase the risk of falls in older people. J AmGeriatr Soc 2002;50(11):1760–6.

79. Harwood RH, Foss AJ, Osborn F, et al. Falls and health status in elderly womenfollowing first eye cataract surgery: a randomised controlled trial. Br J Ophthalmol2005;89(1):53–9.

Visual Risk Factors for Falls 581

80. Foss AJ, Harwood RH, Osborn F, et al. Falls and health status in elderly womenfollowing second eye cataract surgery: a randomised controlled trial. Age Ageing2006;35(1):66–71.

81. Day L, Fildes B, Gordon I, et al. Randomised factorial trial of falls preventionamong older people living in their own homes. BMJ 2002;325(7356):128.

82. Cumming RG, Ivers R, Clemson L, et al. Improving vision to prevent falls in frailolder people: a randomized trial. J Am Geriatr Soc 2007;55(2):175–81.

83. Haran MJ, Lord SR, Cameron ID, et al. Preventing falls in older multifocal glasseswearers by providing single-lens distance glasses: the protocol for the VISIBLErandomised controlled trial. BMC Geriatr 2009;9:10.

84. Haran MJ, Cameron ID, Ivers RQ, et al. Effect on falls of providing single lensdistance vision glasses to multifocal glasses wearers: VISIBLE randomisedcontrolled trial. BMJ 2010;340:c2265.

85. Campbell AJ, Robertson MC, La Grow SJ, et al. Randomised controlled trial ofprevention of falls in people aged > or 575 with severe visual impairment: theVIP trial. BMJ 2005;331(7520):817.

86. La Grow SJ, Robertson MC, Campbell AJ, et al. Reducing hazard related falls inpeople 75 years and older with significant visual impairment: how did a success-ful program work? Inj Prev 2006;12(5):296–301.