Visual Impairment and the Risk of Falling

by | September 2012

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As people age, falls become more prevalent and more dangerous. Impaired vision is an important risk factor for falls in the elderly; and while this is often correctable, it is important to choose vision correction strategies appropriate to patients at risk for falls.

As we age, falls become much more frequent. Of people 65 and older, about a third report falling at least once per year, with about half of these reporting multiple falls.1,2 More than half of all hospital admissions in this population are due to fall-related injury.1-3

Not only is falling a frequent event among the elderly, it causes significant morbidity and mortality: more than 80% of accidental deaths in people over 65 are due to falls.1-3 Falls can also have devastating psychological consequences in elderly people, resulting for many in a loss of confidence and a reluctance to venture outside the home.

Risk Factors

Falls have traditionally been viewed as accidents that are unpredictable and unavoidable, but although falls in the elderly have many causes, they are associated with identifiable intrinsic and extrinsic risk factors. Intrinsic factors include increasing age, female gender, gait and balance impairment, underlying systemic conditions (such as arthritis, postural hypotension, stroke, diabetes, and Parkinson’s disease), sedative use, taking four or more medications, a history of falls, and visual impairment.1-4

Extrinsic factors can include poor lighting, loose rugs, inappropriate footwear, unsafe stairways (no handrail and steps of variable height), irregular floors, and unsuitable bed and bath designs.3

The risk of a fall increases with the number of risk factors. Tinetti and colleagues reported a falls rate of about 8% per year for patients with no risk factors, increasing with each additional risk factor to a 78% falls rate in people with four or more risk factors.4

Visual Impairment

Epidemiological studies have emphasized the role of visual impairment in falls; and the prevalence of visual impairment increases with age: up to 30% of 65-year-olds have impaired vision (defined as binocular visual acuity worse than 20/40).1-5 One surprising finding is that most (66% to 80%) of the visual impairment in patients admitted following a fall is correctable, either by updating a spectacle prescription or the surgical removal of cataract.6,7 Uncorrected refractive error and unoperated cataract are surprisingly common among the elderly of developed countries, suggesting that appropriate ophthalmic interventions could significantly reduce the number of falls in older people.8

To date, not all studies with ophthalmic interventions and cataract surgery have shown the expected reduction in falls rate, although a recent study of the relationship between cataract surgery and hip fractures made use of US Medicare data to look at patients with a cataract diagnosis who either had or hadn’t had cataract surgery.2 When results were adjusted to include age and comorbidities, cataract surgery was found to be associated with a 16% decrease in the odds of hip fracture; and in patients with severe cataract, surgery was associated with a 23% reduction in the adjusted odds of hip fracture.9

 
Vision and Gait

Vision impairment increases the likelihood of tripping over unseen obstacles or misjudging the position of step edges or curbs. Indeed, stairs, steps, and curbs are the most common causes of falls in older people with poor vision.10,11 Vision is also fundamentally involved in basic balance control: The visual system works in concert with the somatosensory and vestibular systems to control postural stability; and postural stability is reduced when the eyes are closed.

We rely even more on the visual system to control balance when the information from the somatosensory and vestibular systems is disturbed (as it may be in diabetic peripheral neuro-pathy or Meniere’s disease).12 Blurred vision in either or both eyes will decrease postural stability and lead to adaptive gait changes. This may be particularly true of blurred vision in one eye (eg, with monovision induced by intraocular lens implantation or contact lens wearing), as this reduces stereoacuity, which is thought to help with adaptive gait.2

Older people with vision impairment tend to adopt cautious strategies when negotiating stairs: stepping more slowly so that a trip is less likely to become a fall, and lifting each foot higher to avoid catching a step edge.13 These strategies help, but they can also prolong the single-support phase of the step (in which only one foot is on the floor). This is the most dangerous part of the step motion, and remaining in this position can increase the likelihood of sideways falls.14

Spectacles and Falls

Studies have indicated that bifocal and progressive lens wearers have a higher risk of “edge of step” accidents, and that older, frailer wearers of bifocals or progressive lenses are twice as likely to fall as single-vision lens wearers.15-17 A large percentage of these falls have been reported to occur outside the home, presumably due to obstacles unseen because of blur in the lower visual field.16 Higher add powers accentuate this effect.

Other attributes of bifocals that may lead to a greater risk of falls include image jump and even diplopia at the bifocal edge.18 For progressive lenses, peripheral distortions and swim, plus the lower visual field blur, are likely what increase risk; these are, again, greatest when the add power is highest.17-19

In a recent randomized, controlled trial in Australia, long-term bifocal or progressive lens wearers were given a pair of distance-only single-vision spectacles for outdoor use. The control condition was continued multifocal spectacles wear. Investigators found that single-vision lenses reduced falls in active patients but increased them among inactive participants.19 The single-vision glasses prescribed were tinted or photochromic (likely offered to boost recruitment), so any decrease in the number of falls could have been due to a combination of improved acuity from distance-only lenses and reduced glare.

Spectacles for Older Patients

As a first step, elderly patients should schedule regular eye exams and be referred early for first-eye cataract surgery. It may help to ask elderly patients whether they remove their glasses to negotiate stairs, a fairly common strategy among older progressive and bifocal lens wearers. Stair safety advice will be particularly useful for these patients.

Long-term wearers of bifocals or progressive lenses with minimal ametropia may reduce their risk of falling by removing their glasses when walking outdoors. Those with significant ametropia who are active may benefit from wearing distance-only glasses when they leave home (other than for driving or shopping).

If at-risk patients are accustomed to wearing single-vision glasses, it may be best to avoid prescribing multifocal lenses for them. Prescription changes should be made conservatively in elderly patients.20 For patients with multiple risk factors for falling, the prescription should not change by more than 0.75 D of sphere, with even smaller changes in cylinder correction, particularly if the axis is oblique.2 To help patients, have them begin wearing new glasses only in the home so that they may get used to them in familiar surroundings. Afterwards, instruct them to wear the new glasses as much as possible without switching back to their old favorites.

THE BOTTOM LINE

Falls are common in, and very dangerous to, the elderly. Vision impairment stands out among many risk factors for falling and can be managed by regular eyecare visits, early referral for first-eye cataract surgery, avoidance of monovision, and care in prescribing bifocal or progressive spectacles. Clinicians should be conservative in making prescription changes in older patients with multiple risk factors for falling; and these patients should be counseled about reducing their risks both inside and outside the home.


David B. Elliott, BSc(Optom), PhD, MCOptom, FAAO, is professor of clinical vision science at the University of Bradford School of Optometry and Vision Sciences, in Bradford, UK. He was assisted in the preparation of this manuscript by Refractive Eyecare managing editor Jennifer Zweibel.
 
 
 
 
 
 
 
References

1. Black A, Wood J. Vision and falls. Clin Exp Optom. 2005;88:212-22.

2. Elliott DB. Falls and vision impairment: guidance for the optometrist. Optom in Pract. 2012;13:65-76.

3. Lord SR, Sherrington C, Menz HB, Close J. Falls in Older People: Risk Factors and Sstrategies for Prevention. 2007, 2nd edition, Cambridge: Cambridge University Press.

4. Tinetti ME, Speechley M, Ginter SF. Risk factors for falls among elderly people living in the community. New Eng J Med. 1988;319:1701-7.

5. Rubenstein LZ, Josephson KR. The epidemiology of falls and syncope. Clin Geriatr Med. 2002;18:141-58.

6. Jack DI, Smith T, Neoh C, Lye M, McGalliard JN. Prevalence of low vision in elderly patients admitted to an acute geriatric unit in Liverpool: elderly people who fall are more likely to have low vision. Gerontology. 1995;41:280-5.

7. Cox A, Blaikie A, Macewen CJ et al. Optometric and ophthalmic contact in elderly hip fracture patients with visual impairment. Ophthalmic Physiol Opt. 2005;25:357-62.

8. Evans BJ, Rowlands G. Correctable visual impairment in older people: a major unmet need. Ophthalmic Physiol Opt. 2004; 24:161-80.

9. Tseng VL, Yu F, Lum F, Coleman AL. Risk of fractures following cataract surgery in Medicare beneficiaries. JAMA. 2012;308(5):493-501.

10. La Grow SJ, Robertson MC, Campbell AJ, Clarke GA, Kerse NM. Reducing hazard related falls in people 75 years and older with significant visual impairment: how did a successful program work? Inj Prev. 2006;12:296-301.

11. Startzell JK, Owens DA, Mulfinger LM, Cavanagh PR. Stair negotiation in older people: a review. J Am Geriatr Soc. 2000;8:567-80.

12. Anand V, Buckley JG, Scally A, Elliott DB. Postural stability in the elderly during sensory perturbations and dual tasking: The influence of refractive blur. Invest Ophthalmol Vis Sci. 2003;44:2885-91.

13. Heasley K, Buckley JG, Scally A, Twigg P, Elliott DB. Stepping up to a new level: Effects of blurring vision in the elderly. Invest Ophthalmol Vis Sci. 2004;45:2122-8.

14. Buckley JG, Heasley K, Scally A, Elliott DB. The effects of blurring vision on medio-lateral balance during stepping up or down to a new level in the elderly. Gait Posture. 2005; 22:146-53.

15. Davies JC, Kemp GJ, Stevens G, Frostick SP, Manning DP. Bifocal/varifocal spectacles, lighting and missed-step accidents. Safety Sci. 2001;38:211-26.

16. Lord SR, Dayhew J, Howland A. Multifocal glasses impair edge-contrast sensitivity and depth perception and increase the risk of falls in older people. J Am Geriatr Soc. 2002;50:1760-6.

17. Johnson L, Buckley JG, Scally AJ, Elliott DB. Multifocal spectacles increase variability in toe clearance and risk of tripping in the elderly. Invest Ophthalmol Vis Sci. 2007;48:1466-71.

18. Walsh G. Vertical diplopia on downgaze with bifocals. Optom Vis Sci. 2009;86:1112-6.

19. Haran MJ, Cameron ID, Ivers RQ, et al. Effect on falls of providing single lens distance vision glasses to multifocal glasses wearers: VISIBLE randomised controlled trial. BMJ. 2010;340:c2265.

20. Elliott DB, Chapman GJ. Adaptive gait changes due to spectacle magnification and dioptric blur in older people. Invest Ophthalmol Vis Sci. 2010;51:718-22.



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