Smoked salmon in three dimensions

Susan R Barry defied scientists by fixing her eyes – then, in Oliver Sacks, made a friend of the mind

272pp, Ithaka, T £14.99 (0844 871 1514), RRP£16.99, ebook £12.99

“The man who mistook his patients for a literary career” is how the disability-rights activist Tom Shakespeare dismissed the late neurologist Dr Oliver Sacks. It’s true that not all of Sacks’s patients had much say in how he turned their unusual conditions – such as being eternally stranded in 1945 by amnesia, or temporarily awakened from postencephalitic fog by the new drug L-dopa – into what he called “neuro-novels”. But surely anyone who has read Sacks knows that he was a compassionate advocate for, not an exploiter of, the voiceless? For those who haven’t, fresh testimony is given by a case study whom he nicknamed “Stereo Sue”.

Dr Susan Barry was born crosseyed. Though she underwent three surgeries to her eye muscles to straighten her gaze – at the age of two, three and seven – she could still only see the world in 2D for almost five decades. As a professor of biology and neuroscience at Mount Holyoke College, in Massachusetts, Barry was familiar with the 50 years of clinical research that appeared to prove that brain-eye co-ordination for stereo vision could only develop in early childhood. She’d lectured on the subject herself. So nobody was more surprised than Barry when she learnt, aged 48, to see the world in its full and glorious depth.

In her mid-40s, Barry noticed objects in the distance “jittering”. She sought the advice of an optometrist, who recommended a vision exercise. She was shown how to hold a “Brock string” – featuring a series of beads on a short length of cord – up to her nose with one hand and away from herself with the other. Driving home from her first session, Barry was astonished to find the steering wheel appear to “pop out” from her car’s dashboard. The next time she tried the exercises, the rear-view mirror also popped out of the windscreen.

Over the next few months, the usually levelheaded Barry found herself overwhelmed by “joy, childlike glee” at her extraordinary new perception of everyday objects: taps, flowers, her own fingers. Suddenly, she felt a part of scenes – such as snowstorms – of which she’d previously only felt herself to be a passive observer.

But who would believe that she’d defied scientific knowledge, and help her spread the news that might allow other stereo-blind people to share her 3D delight? She wrote to Sacks, and he immediately replied suggesting a meeting. She was canny enough to suspect he’d find her equally interesting as a delusional. But he listened to her, tested her and ultimately believed her. When Sacks came to write about Barry, he sent her his essay for approval and took in her changes. The pair continued exchanging letters and deepening a friendship that would last until his death in 2015.

Their letters are all reproduced in this charming book, which transports readers into a world of preinternet polymaths that seems almost Victorian. Sacks and Barry share theories on the possible sentience of ferns and the visual capacity of squid. They both play Bach on their pianos and devour a staggering number of books. They meet up to swim in bioluminescent waters and debate philosophy over smoked salmon. Their mutual wonder at the physical wonders of the universe is infectious. Their witty, affectionate puns made me laugh. Together they proved not just the possibilities of later-life stereo vision but of late-life friendship.

On gaining stereo vision, Barry could see snowstorms as she never had before

Alas, cancer took Sacks’s own stereo vision only a few years after Barry gained hers. A shy man, he is cautious with details of his decline, although he is frank with her about suicidal urges provoked by chronic pain. His letters to Barry don’t mention his late-life coming out as a gay man or the tender partnership he forged in his 70s with the writer William Hayes after 35 years of celibacy. But we do see him proving his critics wrong by encouraging Barry to publish her own story.

Fans of either Sacks or Barry’s work will already know much of the meat of Dear Oliver. But for everyone else, there’s something very moving about the quirky world of their correspondence. Yes, there’s plenty of sadness here; but what will survive of them both is their close attention to the world, and their electric enthusiasm for life.