When does vision become a life and death matter? That’s right. Driving.
Which makes the visual standards for obtaining a driver’s license in the United States very curious. In most states, initial evaluation for teenagers only requires a screening for visual acuity. The legal requirement is typically 20/40 or 20/50 best corrected acuity in the better eye. The odd thing is that no one has ever established that static visual acuity has any bearing on driving safety. It’s relevance is related more to the ability to read signs at a specified distance. The more pertinent tests might be dynamic visual acuity, depth perception at distance, contrast sensitivity, and measures of central/peripheral balance including peripheral awareness, visual field, and useful field of view. In essence visual driving standards suffer from the same problem that plagues school vision screenings: over-reliance on the Snellen Eye Chart because it is a cheap, convenient, and readily available visual function – but one that has little bearing on actual performance.
The Science Times section of today’s New York Times featured a nice article on Cognitive Roadblocks to a Rite of Passage. It highlighted the challenges of a young woman who is having trouble learning to drive because of attention deficit difficulties. It mentions the importance of having an examination that looks at visual processing. That is a start in the right direction. We are increasingly collaborating with occupational therapists to help not only to help older patients with driver re-entry, but to help young patients who are having difficulty learning to drive.
In the online versionof the Times, the question of how well individuals with Asperger’s Syndrome are equipped to drive is explored. Driving, particulary driving defensively, requires social empathy. One might say there’s a certain degree of visualization involved – you literally have to learn to make visual judgments anticipating other driver’s visual viewpoints. We have a substantive contribution to make for many patients with visual cognitive challenges that go well beyond the legal requirements to drive. These issues deserve more of our collective attention.
– Leonard J. Press, O.D., FCOVD, FAAO
The VisionHelp Blog 
Indeed, driving is one function where stereo blindness and lack of peripheral awareness are a major issues, and yet there is no screening. In fact, when I wanted vision therapy to train my eyes to work together (I am an alternating esotrope), my optometrist questioned my need for binocularity because I had driven for 30+ years without incident and can read. Acuity, with the ability to read, has been the bar, even for optometrists.
Now that I have also lost upper half of my retinal function in my “good” eye, I can attest that driving is at times alarming to me. First, cruising down the highway with my left eye perspective is radically different than with the right. I used to love the left lane, because I had better peripheral vision to my right (and the lane is typically empty). Now I drive in the middle or right lane, because the guard rail to the left appears to be uncomfortably close!
I am even more alarmed by what recently appears to be increasing peripheral vision and optic flow, where the added volume of space and enhanced perspective with closer things appearing closer and further things appearing farther away affects my judgement to the point where I at times feel like I may be over-correcting eg. when I see a pedestrian. Left hand turns in busy traffic and passing are even more stressful than before…
Excellent points, Lynda. Thanks for taking the time to comment and share your perspectives as a patient.