Post-cataract surgery focus of driving risk study
http://www.sciencewa.net.au/topics/health-a-medicine/item/2259-post-cataract-surgery-focus-of-driving-risk-study.html
A RECENT study has found testing visual acuity alone may not be enough to identify all visually impaired drivers who are at risk on the road.
Contrast sensitivity, not visual acuity (the standard visual test for assessing driving ability), was associated with driving difficulty in patients who had undergone first eye cataract surgery.
Researchers at the Curtin-Monash Accident Research Centre (C-MARC) assessed self-reported driving difficulty in 99 older bilateral cataract patients before and after they received surgery on one eye.
Most cataract surgery is performed on one eye at a time and there are usually long waiting times before public hospital patients can receive second eye surgery, so understanding how driving difficulty is affected by first eye surgery may help licensing authorities develop improved visual tests for older drivers, according to the researchers.
They found all visual variables tested – visual acuity, contrast sensitivity, stereopsis (a type of depth perception) and useful field of view – significantly improved in the surgery eye.
However, only the change in contrast sensitivity was significantly associated with changes in self-reported driving difficulty; the other three variables had no significant effect.
This supports previous studies that have highlighted the importance of contrast sensitivity in assessing driving difficulty, according to C-MARC researcher Michelle Fraser.
“This suggests that using visual acuity alone may, firstly, not identify all those who are at risk on the road due to visual impairment and secondly, lead to the restriction of older drivers who are not significantly impaired,” she says.
“As the driving population ages, we believe it is very important for licensing authorities to further investigate the role of contrast sensitivity as a potential screening test for licensing.”
Other stand out results include 16 per cent of patients reporting no improvement in driving difficulty, while 11 per cent reported experiencing more difficulty after the surgery.
Ms Fraser suggests the un-operated eye was probably interfering with vision, highlighting a need to prioritise cataract patients for first and second eye surgery.
“While first eye cataract surgery almost always brings about visual improvements, for some bilateral patients, this improvement can result in large differences in vision between the operated and un-operated eyes,” she says.
“This is probably why driving difficulty did not improve or worsened for a significant proportion of participants despite improvements in visual acuity and contrast sensitivity.”
C-MARC, which has a program of research in older drivers with visual impairment, plans to carry out further study using a driving simulator to investigate the effect of a range of visual conditions on driving ability.