PHILADELPHIA, May 22, 2019 /PRNewswire/ -- In a study recently presented at the major vision research conference, The Association for Research in Vision and Ophthalmology (ARVO) researchers from Wills Eye Hospital in Philadelphia studied the rate of car accidents in patients with glaucoma. They found that the rate of those accidents among patients with moderate glaucoma and with mild vision loss was almost five (5) times higher than expected for Pennsylvania drivers in this age group. As a patient's vision declines, doctors are often asked by families what to do: should their loved ones still be driving?
The study followed a group of 161 patients with an average age of 64 with moderate open angle glaucoma in at least one eye over 4 years. Each year, patients were asked if they were a driver in any motor vehicle accidents during the previous year. The study evaluated different aspects of vision, such as visual acuity, peripheral vision and contrast sensitivity – whether you can tell not just black or white but can you differentiate between dark gray from light gray. It also considered patients' ability to do certain normal daily activities like reading street signs and finding objects on a crowded shelf. "What we found was between 5% and 10% of these glaucoma patients were involved in motor vehicle accidents each year despite still having vision good enough to legally qualify for driving," said Jonathan S. Myers, MD, Chief of the Wills Eye Hospital Glaucoma Service who was involved in the study and a presenter at the research conference. This compares to a 1.1% rate of MVAs for drivers of similar age to these (61-65 years old) reported by 2017 Pennsylvania Crash Facts. In the study, the National Eye Institute Visual Function Questionnaire was used measuring vision-related quality of life and the Glaucoma Symptom Scale measuring eye comfort at each of the visits.
"One finding that stood out was that interestingly, it was the peripheral vision in the worst eye that made the biggest difference. That suggests that in some study patients, significant blind spots existed which could have been a liability for driving," said Myers. For most states, the legal vision requirements for driving, are 20/40 vision for night and 20/70 for daytime driving, although daytime driving requirements vary. 20/40 means that you can see at 20 feet what a person with "perfect vision" would see at 40 feet – so about half as sharp. Some states also require between 120 and 140 degrees of side to side vision for driving- that's about 12 hand-widths at arm's-length.
"It's a very common predicament especially as we have an increasingly aging population - vision disturbances are more common as we grow older," added Myers. The most common causes of reduced vision are cataracts – which can be fixed, followed by macular degeneration in a Caucasian population and glaucoma in the African American and Hispanic populations. Glaucoma is not reversible; the sight in macular degeneration can be improved in some cases. "It's increasingly common to address driving with families. Driving isn't simply about driving, it's also about independence for an aging population so these can be very difficult and emotional conversations. As doctors, we need to care for the whole patient and be part of the care team with the family," noted Myers. While further research is needed, these findings suggest that:
- An impaired visual field in either eye was found to be an independent risk factor for motor vehicle accidents in patients with moderate glaucoma.
- Identifying individuals at risk for accidents may help prevent accidents by educating providers and patients with glaucoma regarding their safety and fitness to drive.
- Don't be afraid to have that conversation as a family with a loved one or with the family doctor or ophthalmologist. Patients with glaucoma along with their family members should talk about this – whether it's with an ophthalmologist, optometrist, or primary care physician.
SOURCE Wills Eye Hospital