Acquiring stereo vision as an adult

[rjlittlefield]

Recently I became aware of the case of Susan Barry, a person who developed strabismus in early infancy and as a result never developed the ability to see in stereo, but who suddenly acquired stereo vision at the age of 48 as an unexpected side effect of behavioral therapy designed to help her two eyes work together.

This late-in-life acquisition came as a great surprise to Dr. Barry, who as a professor of neurobiology had long taught her students that there are "critical periods" for developing such capabilities, and if you don't get them then, you never will.

As a lover of stereo, and an optimist about neuroplasticity, I find Dr. Barry's account of her experience to be fascinating on many levels.

If any of this interests you, then I suggest to visit http://www.stereosue.com/ and follow the links in the first paragraph.

Dubbed “Stereo Sue” by neurologist Oliver Sacks in a New Yorker article by that name, Sue Barry has gone on to write her own book Fixing My Gaze which describes the astonishing experience of gaining 3D stereovision after a lifetime of seeing in only two dimensions. Intensive vision therapy created new neural connections, and with them, a new view of the world. Challenging conventional wisdom that the brain is programmed for life during a critical period in childhood, Barry offers a poignant and revelatory account of our capacity for change.

The article at newyorker.com is an excellent place to start. Despite lots of reading about stereoscopy over the past several decades, much of the material in the article was new to me.

I have read the book also, once through from start to end, and I'm currently starting my second pass.

--Rik

[Chris S.]

I've lately been accompanying a family member to specialists for diagnosis and treatment of strabismus that came on suddenly at age 80. One of these specialists is a neuro-ophthalmologist. During the exam, his assistant had the patient don a pair of polarized eyeglasses and look at a stereo image of a fly. Said the assistant to the patient: "Pick up the fly by its wings." The patient pinched two fingers together flush on the surface of the page.

Then the assistant handed me the glasses and said, "Here is what she couldn't see." To my eyes, the fly was vividly three-dimensional, with its wings sticking up from the page approximately at 45-degree angles. The assistant added, "A person with normal stereo perception pinches her fingers together about an inch above the page."

A simple, clever test. I found it interesting to see a stereo macro image used as a diagnostic tool. The test device, shown in the above link, also had more subtle stereo perception images. The patient, having demonstrated no gross stereo perception, could not even imagine what she was supposed to see in the tests for fine stereo perception. In my brief look, I could perceive some of the fine test patterns, but not all.

Since I'm writing this, I'll add a bit more info in case anyone ever encounters something similar. Sudden-onset misalignment of vision (strabismus) or double vision (diplopia) should be treated as an emergency, with medical evaluation for potential stroke. In my family member's case, this meant hospital admission and a battery of tests, which thankfully came out negative. If stroke has been ruled out, the search for a cause can proceed with less haste. In the particular case at hand, the issue appears to be thyroid eye disease, an autoimmune disorder that we don't understand very well. Treatments include corticosteroids, a new monoclonal antibody drug, Tepezza, that is priced to complete with a modest house, and surgery to relieve symptoms.

--Chris S.