Owing to their widespread occurrence and deleterious impact, falls and their consequences continue to pose a major public health concern among older adults worldwide [1]. Even in the United States (U.S.), a highly advanced developed country, approximately one in three adults over age 65 experiences a fall on an annual basis [2]. Among those who survive, 20 to 30% have been found to suffer moderate to severe injuries that commonly reduce mobility and limit independence, even after controlling for chronic conditions and functional disabilities at baseline [3]. As well, about two-thirds of first-time fallers will experience a second fall within a six-month period [4], approximately 42% will result in hospital admissions with a mean length of stay of 11.6 days, and approximately 50% of fall injury events that occur at home and require hospital admission will result in discharge to a nursing home [5]. Due to these and other complications including fear of falling and dependence [6], the physical, social, and morbidity costs as well as the direct economic costs of treating fall injuries are consequently highly substantial [2]. Additional complications of multiple falls include significantly increased functional disability, and poorer responses to the prevention of nursing home falls [7].

Much research has consequently been implemented to examine risk factors for falls other than age that might be amenable to prevention, and fortunately a vast body of this research shows a number of modifiable factors can explain the high rate of falling among the elderly, both in the community and in the nursing home setting. This is important as the incidence of fall-related injuries and deaths, along with the costly disabling consequences of falls to both the individual and society in general are rising along with the average age of current populations such as the United States [8]. Indeed, it would seem imperative, more than ever, to continue to identify and categorize those predisposing risk factors for falls that are amenable to change and to apply this information in an optimal manner to prevent or allay the aforementioned highly deleterious cycle of events, found to be experienced by one third of persons over age 65, and about one in two over age 80 each year [9].

Focusing on identifying commonplace risk factors for falling seems an especially reasonable idea, because probably fewer than 10 percent of all falls result from overwhelming intrinsic causes such as a loss of consciousness or extrinsic causes such as being hit by a car [10]. Rather, cumulative evidence indicates that among the elderly, factors deemed most likely to contribute to falls and fall injuries are: physical frailty, physical inactivity, alcohol misuse, cognitive and sensory impairments [9], visual impairments and visual cognition [11], neurological and musculoskeletal disabilities, psychoactive medications, and difficulties in gait and balance [12, 13], most of which may be somewhat amenable to well-designed remedial interventions. Other factors include the use of inappropriate eyewear [14], the overuse of psychoactive medications [15], comorbid conditions and being underweight [16] or overweight with severe polyneuropathy [17].

In addition, environmental factors such as slippery surfaces, uneven floors, poor lighting, loose rugs, unstable furniture items, and a variety of obstacles and objects on floors may pose further risk of falling and serious injury [17]. Other documented risk factors for falls include a variety of pathologic or disease states of later life leading to sedentary behaviors [18]; health and functional status [19], and individual behavioral factors such as risk taking [20]. The failure to seek appropriate assistance from health care professionals and to employ prescribed preventive strategies [21] and the lack of targeted preventive and treatment services and other community resources are specific socioeconomic risk factors [22] that may also influence the risk of falls.

Since the risk of falling increases incrementally with the number of prevailing risk factors [9], falls from multiple physiological risk factors usually result in recurrent falls [23], and since the incidence of fall-related injuries and deaths is rising along with the average age of current populations such as the United States [8], reducing one or more preventable fall-related risk factors might carry with it a proportionate reduction in fall frequency and injury risk [10]. Evidence based strategies to reduce modifiable falls risk factors include physical activity programs to improve strength [24, 25], balance and coordination [26], supervision to minimize the use of psychoactive medications [27], interventions that maximize control of comorbid conditions [27], and environmental assessments and modifications [28]. Others include the use of hip protectors [16], as well as specific shoe types and dietary amendments and supplementation [25]. While mentioned in the research on this topic, much less emphasis has been placed on vision and its impairment as a potent and independent risk factor for falling in people over the age of 60 years [11].

This paper focuses on vision as a risk factor for falls, and reviews relevant research literature on how vision loss, a highly common age associated disability [11], can influence the risk for falls, as well as how efforts to minimize vision loss and promote vision can reduce the risk for falls among community-dwelling older adults.

Visual impairments, highly prevalent in the elderly [29] are commonly associated with poor depth perception, which comprises binocular stereopsis or the ability to perceive objects in three dimensions and monocular cues implicating depth and motion cues [30]. They are also associated with a reduced ability to perceive contrast [31], which involves the ability to detect stimuli of varying brightness against a background of given brightness [30]. In this regard, Legood et al. [31] found elderly people with reduced visual acuity, a measure of spatial resolution used for perceiving fine detail [30] were 1.7 times more likely to fall and 1.9 times more likely to have multiple falls compared with fully sighted populations. Moreover, poor distance visual acuity reportedly increased the risk of fractures related to falling [32, 33], quite markedly, as did the presence of a visual impairment, in general [34]. Klein et al. [35] similarly noted that the odds ratios for 2 or more falls in the past year for the poorest categories of visual function were 2.02 (95% CI, 1.13, 3.63) for current binocular acuity and 1.85 (95% CI, 1.10, 3.12) for visual sensitivity, and French et al. [36] noted a link between injurious falls, and moderate, rather than severe self-reported visual impairments.

Although difficult to attribute directly to vision, since many confounding factors prevail among the elderly, in light of reasonably compelling evidence in some studies that vision loss increases the risk of frequent falls [37], Reed-Jones et al. [11] has proposed that impaired vision is undoubtedly an important independent risk factor for falls, albeit an often underreported and underrepresented one in the context of research. This is consistent with earlier observations by Harwood [30] who found poor visual acuity, variously defined, almost doubled the risk of falling. As well, Patino et al. [38] found both central as well as visual peripheral impairments increased the risk for falls and falls with injury after initial examination in a dose-response manner.

In addition to age-related macular degeneration, presbyopia or a problem requiring bifocal corrective lenses, diabetic retinopathy, and glaucoma can all cause various forms of visual impairment that can raise falls risk [11, 30]. Lord et al. [39, 40] found that among the reasons why limited or disturbed vision may heighten the risk for falls was the use of multi-focal lenses, which can impair distance contrast sensitivity and depth perception, thus reducing the ability of the affected person to detect obstacles or environmental hazards [11]. Similarly the temporary loss of focus on stairs when wearing bifocal lenses can cause misjudgment of depth [30]. Bifocal lenses may also increase the risk for injurious falls in the outdoors because of the increased propensity to trip or estimate unexpected barriers or objects [11].

Limited vision may also have an adverse effect on mobility when negotiating a raised surface such as a step [41], as well as adversely affecting horizontal toe clearance and vertical toe clearance [42], as well as balance [43], and posture control [44] or both, thus potentially increasing the risk of falling when negotiating stairs [45], as well as when walking. This is primarily because the elderly are more dependent on open loop control signals related in part to visual stimuli and influx for purposes of optimizing postural control [46]. As well, the presence of compromised vision can reduce one’s ability to respond in a timely and effective way to environmental hazards, as can multifocal spectacles [45], monocular blur and monovision correction contact lenses [42].

Another finding is that many medications can cause visual disturbances that can similarly heighten the risk for falls, as may topical eye medication [30] even if vision is not actually impaired [11]. Glynn et al. [47] who analyzed serious falls determinants among elders with glaucoma and at least one prior fall found the greatest single risk factor for falls was the use of nonmiotic topical eye medications. Other factors associated with the risk of falls were use of miotic eye medications, and visual field impairment, suggesting that ocular and systemic medications are the major predictors of falls even in this elderly population seeking ophthalmologic care for glaucoma, and that certain medications may pose a greater risk for falls than major visual impairment.

It is also reported that severe binocular visual field loss greatly increases rates of falling [48], as does reduced visual acuity [49], which worsens after age 50, regardless of the presence of pathology [30]. Not surprisingly, impaired vision, which affects a high proportion of older individual [50] is found to be an independent risk factor for hip fractures, frequently caused by falls [32], and among the Framingham Study Cohort, the fracture rates in those with moderately impaired vision to poor vision were higher than in those whose vision was considered good [51]. Further, those with moderately impaired vision in one eye and good vision in the other had higher risk of fracture than those with a similar degree of binocular impairment.

Klein et al. [52] found that for persons 60 years of age and older, hip fractures after the age of 40 were significantly related to all measures of visual function, and that time to walk a measured course was significantly related to all measures of visual function. They suggested their findings supported a consistent relationship between falls, fractures, gait time, and visual functions. Specific problems identified by Ivers et al. [53] that influence the risk of hip fracture were binocular visual acuity worse than 20/60, having poor vision in both eyes, having no depth perception, varying degrees of decreasing stereopsis, self-reported poor vision, not wearing glasses at the time of the fall, and increasing time since the last eye examination.

Close et al. [54] who assessed visual acuity with a Snellen chart, defined impaired vision as present where acuity was 6/12 or worse in either eye, or being partially sighted if corrected vision in both eyes was 6/24 or worse, or being blind if acuity was 6/60 or worse in both eyes. Poor binocular vision was defined as a disparity in acuity between the visual acuity of the eyes. Results showed 89 (59%) patients had visual impairment, and 94 (62%) had poor stereoscopic vision, and 53 (35%) had cataract formation in one or both eyes. Patients were 65 years and older, living in the community, who had presented to an accident and emergency department with a fall history.

In a retrospective case control study by Kantayaporn [55] that aimed to identify the factors of a fall that caused fractures including, gender, underlying diseases, chronic drug use, history of parent fragility fracture, age of menopause, steroid used, body mass index, visual acuity and a timed get up and go test, multivariate regression analysis of 336 cases of fractures in 1,244 cases of fall showed significant factors for the falling and fracture group that were different from falls without a fracture group. These factors included age, female gender, menopause before age 45 and visual impairment. In addition, visual impairment was the key factor other than osteoporosis implicated in falls that resulted in fractures. The author suggested that fracture prevention programs for the elderly should include attention to the correction of any prevailing visual impairment, not only osteoporosis related treatments.

Salonen and Kivela [23] who examined the evidence concerning poor depth perception/stereo acuity and poor low-contrast visual acuity as risk factors of recurrent falls found this quite convincing. Risk factors identified were discrepant vision, a decrease in visual acuity, and loss of visual field, although the results concerning the relationships between poor visual acuity and poor contrast sensitivity and the risk of recurrent falls were less clear.

Skalska et al. [56] who examined factors influencing falls risk among Poles, found visual impairment to be more frequent in fallers 55-59 years of age and 65 years and older. In the younger group, moderate vision impairment was found in 31.05% of non-fallers and 39.57% of fallers, and significant visual impairment or blindness was diagnosed in 0.35% of non-fallers and 1.69% of fallers (p=0.003). In the older non-fallers moderately impaired vision was present in 39.45% of cases studied and severe vision impairment was present in 1.67% of cases, while in fallers, the rates were 44.85% and 3.36%, respectively (p=0.0002). A higher frequency of vision impairment in fallers was found in both genders. That is, moderate vision impairments were found in 41.31% of men and 44.76% of women, and severe impairments were found in 3.10% of men and 2.98% of women, compared to rates among non-fallers where moderate and severely impaired vision was present in 37.15% and 1.15% of men and 36.21% and 1.28% of women. In both age groups, the authors found falls occurred more frequently in subjects with impaired vision, and the percentage of fallers increased with the severity of impairment.

French et al. [36] who analyzed injurious falls and related self-reported incapacities found an increased odds of injurious falls with moderate visual impairment. The observation that moderate but not severe visual impairment was predictive of a past fall was noteworthy. The authors felt that those with more severe impairment might be more cautious than those with less severe vision impairments. They also suggested that visual dysfunction, is not a single sensory problem, but may be more complex than this and can contribute to falls through a number of different mechanisms. This is consistent with findings of Nagamutsu et al. [57] who noted altered visual-spatial attention to task-irrelevant information was associated with heightened falls risk among older adults.

Yet, even though poor vision has been associated with frailty in the elderly, and an increased risk of falls and sustaining a fracture [50], and vision impairments can be both independent or co-occurring risk factors for fall [58], the presence of a visual impairment may go undetected, as far as being a possible risk factor for future falls, and guidelines for preventing falls generally only focus on vision in a very limited way, even though some of these conditions are treatable [50]. Moreover, few focus on visual cognition as a separate or co occurring risk factor despite increasing evidence that this function plays a key role in motor processing and anticipation [11]. In terms of falls-related prevention programs, Gillespie et al. [24] who examined the efficacy of randomized controlled trials of interventions designed to minimize risk factors for falls among the community-dwelling, including the institutionalized and hospitalized elderly, noted that providers contemplating implementation of falls-prevention programs should first consider screening the "at-risk" elderly, and then follow this with intervention programs designed to reduce the risk of falling due to both individual intrinsic and extrinsic causes.

In this respect, understanding what components of vision are most likely to be responsible for increasing the risk for multiple falls [37], as well as other factors that can cause poor vision such as incorrect prescription lenses, scratched lenses, not wearing glasses when needed, the inability to afford lenses, health issues such as diabetes, and vascular abnormalities should be evaluated. While, peripheral vision is reportedly of great importance, especially in outdoor activities, that involve walking in a crowd, in traffic, and on level or irregular ground [58], the most important visual risk factors are said to be reduced contrast sensitivity and depth perception [40]. Multifocal lenses and bi focal glasses may likewise heighten the risk for falling as a result of a reduction in the ability to detect environmental hazards [40, 59]. As well, these individuals may not be able to see a poorly lit bottom step, may not notice surface changes from a carpet to slippery tiles, and their protective responses such as grabbing a rail may be hindered [59].

Unsurprisingly, compared to those without vision impairments Legood [31] found those adults with visual impairments to be seven times more likely to fall and incur serious injury. Reasons for vision deficits include ocular conditions such as diabetic retinopathy, glaucoma, and cataracts. These impairments and others can produce moderate to severe visual impairments that can affect central vision acuity and peripheral vision or both [29], and along with environmental factors such as difficulties in color vision, when perceiving pastel and dark colors, may compromise the ability to judge distances and obstacles or irregularities in the visual field. This is because in many public areas, where pastel colors are used, it may be difficult to detect differences between various surfaces, thus increasing the risk for falls [58].

Although Cummings et al. [60] comprehensive vision and eye assessment, followed by treatment did not reduce falls risk, and may have increased this, strategies that may be helpful for minimizing falls risk among older persons in the community include the timely assessment of visual acuity, contrast sensitivity, and depth perception [61], corrective eye surgery, the prescription of appropriate eyewear, changing glasses, and selected pharmacologic and environmental assessments and interventions [29, 61]. Others have stressed the importance of assessing factors such as visual attention, visual processing, and visual-spatial ability that influence mobility and obstacle avoidance, followed by appropriate treatment, and in cases where it is impossible to reverse the presence of pathology, and restore normal vision, the main aim should be to prevent deterioration [30]. Others who have examined current binocular vision, best-corrected vision, near vision, contrast sensitivity, and visual sensitivity or threshold, recorded using perimetry [35], have suggested that any form of visual impairment may increase falls risk, and since falls risk increases as visual impairment worsens, measures to optimize vision along with the visual environment may be helpful [30]. In addition to correcting refractive errors [53], and possible cataract surgery where indicated [30], the use of single rather than multifocal glasses may help to reduce falls risk [40]. As well, the use of bright colors and contrasts and taking into account the elderly may have red-green vision defects may be helpful when planning public facilities and spaces [58]. Tinetti [62] also discussed the possibility that public health-mandated changes in the environment, such as high-contrast curb and stair markers in public places may prove helpful. As well, appropriate advice about the use of multifocal lenses when walking, and more thought to what would constitute safe and appropriate floor patterns for visually impaired older people might prove useful as well.

Day et al. [63] who did compare a group based exercise, home hazard and vision improvement strategies over a 15 week period, observed that only the exercise intervention had an effect, and although it appeared the intervention improved vision, an increased falls risk was observed. However, numbers actually treated for vision impairments were very low and a clear multidisciplinary approach was not followed. Similarly, simply introducing vision screening for frail older people may not lead to improvements in vision, and hence used in isolation, may provide no direct influence on falls risk, unless more comprehensive approaches, as well as more specific analyses of any prevailing visual problems are forthcoming [64]. In more recent attempts to reduce falls risk, the specific role of vision was not mentioned implicitly, however [65, 66].

Clemson et al. [67] conducted a program called The Stepping On program that included regular visual screening, and making adaptations to low vision, among other interventions to reduce falls among the elderly. The intervention group experienced a 31% reduction in falls, which was deemed clinically significant. In another study, Lord et al. [68] examined whether an individualized falls prevention program comprising exercise, visual, and counseling interventions could reduce physiological falls risk and falls among older people. In this study, 620 people aged 75 and older received individualized interventions comprising exercise and strategies for maximizing vision and sensation; while the minimal intervention group received brief advice; and the control group received no intervention. Results showed subjects assigned to the extensive visual intervention group showed significant improvements in tests of visual acuity and contrast sensitivity. The rate of falls and injurious falls within the trial period were similar in the three groups, however.

Thus, while several studies support a compelling case on theoretical grounds for the potential efficacy of visual oriented interventions in preventing falls and fall-related injuries larger and more well-controlled prospective studies of the community-dwelling elderly at "high risk" for falls that clearly provide tailored vision related interventions such as that by Haran et al. [69] and Fitzharris et al. [70] are needed to establish whether these are efficacious or not. Furthermore, even though Guidelines for the Prevention of Falls in Older Persons have recently been developed under the auspices of the American Geriatrics Society (2001)[20], very few of these guidelines provide insight into how vision interventions and assessments might prove helpful, and vision was not listed as an intrinsic risk factor in a recent review of falls in the elderly [71]. Perhaps more focused comprehensive assessments of vision and actual mobility and postural tests would be helpful for assessing those at risk for falling. This is because altering vision alone may not be sufficient for fostering integrated functional strategies needed in the real world for avoiding hazards.