New Insights into Crash Risk for Older Drivers with Cataract

Cataract surgery is the most commonly performed ophthalmic surgical procedure and approximately 5% of Americans over 70 years of age have cataract surgery each year.¹ Though cataract surgery is highly cost effective and successful,² cataract remains a major cause of preventable vision impairment and blindness.³ Cataract accounts for 39% of blindness and 48% of vision impairment globally.³

In low and middle income countries, there is a shortage of cataract surgical services and in line with the goals of Vision 2020, resources are being allocated to increase cataract surgical coverage.³ In high income countries, there are also delays and inequities in access to surgery.^1,4 In Australia, where Mueleners and colleagues’ research (published in this issue) was conducted,⁵ cataract is the second leading cause of vision impairment after refractive error.⁶ Excluding refractive error, population-based studies in Australia find that cataract accounts for 37% of cases of vision impairment and 13% of blindness.⁶ Though cataract surgery is widely available, waiting times for surgery can vary, with longer waiting times in rural areas and for disadvantaged population groups.⁷ Some individuals can wait up to 2 years for surgery.⁷ A comprehensive understanding of the implications of unoperated cataract is needed to inform policy and allocation of resources to improve access to cataract surgery in such settings.

Cataract causes predictable changes to vision such as reduced high and particularly low contrast visual acuity and increased glare sensitivity. These changes can impact the ability to carry out many activities of daily living such as reading, participating in hobbies, community interaction and safe mobility. A systematic review, investigating the impact of delayed access to cataract surgery, found that waiting times of 6 months or more were associated with increased likelihood of a poor vision outcome after surgery and reduced quality of life.⁸ Further, individuals with vision impairment are at increased risk of falls⁹ and expediting cataract surgery has been shown to reduce the rate of falls amongst older people waiting for first eye cataract surgery in the UK.¹⁰

The impact of cataract surgery on crash risk is less well documented in the literature and the manuscript by Mueleners and colleagues contributes important new information.⁵ Driving is a visually demanding activity so it is not surprising that cataract can impact driving ability and observational studies find that poor contrast sensitivity in drivers with cataract is predictive of crash risk.¹¹ Drivers with cataract report decreased confidence in their driving ability.¹² Bilateral cataract surgery has been shown to improve driving performance when measured on a closed road circuit before and after surgery.¹³ However, the impact of cataract surgery on actual crash risk has been difficult to evaluate, as crashes are a rare event and large sample sizes are needed. In this issue Meuleners and colleagues⁵ use data linkage to combine statewide hospital records with police crash data to assess the impact of cataract surgery on crash risk. It is only through this population-based approach that crash involvement can be investigated with sufficient sample size. The authors were able to review all cataract surgeries performed in a 10-year period in Western Australia between 1997 and 2006, close to 30,000 surgeries. These analyses demonstrated a 13% reduction in crash risk in the first year after first eye cataract surgery.

These findings are important as older drivers are at increased risk of crash involvement per mile driven, and increased risk of serious injury due to the vulnerability of age.¹⁴ This new work included an economic analysis and estimated the cost savings for the crashes averted during this 10-year period, at 4.3 million Australian dollars.⁵ Such information is valuable for policy debate in this area and may serve to motivate resource allocation to cataract surgery waiting lists and promotion of referral for cataract surgery amongst older drivers.

We can anticipate that a large and increasing number of older drivers will require cataract surgery during the later stages of their driving career, based on trends in aging of the population, the increasing numbers of older people who drive and prevalence of cataract in older age groups. An Australian survey published in 2004 found that 39% of patients about to undergo cataract extraction surgery in Australia were current drivers and that one quarter of these had vision worse than the legal threshold at the time of their surgery.¹⁵ The manuscript by Meuleners and colleagues⁵ adds to the body of evidence about the impact of unoperated cataract on driving safety. The reduction in crash risk associated with cataract surgery, lends support for consideration of driving status in both referral for cataract surgical assessment and prioritization for cataract surgery. These results also emphasize the need for appropriate advice on driving prior to cataract surgery. These results are particularly pertinent to highly motorized countries where driving is key to independence for many older members of the community.