After suffering a head injury, I found I was unable to read without headaches, eye strain and wild mood swings – and that my condition was far from rare

In the Palazzo Pitti in Florence hangs a painting by Raphael of the Renaissance humanist, poet, scholar, orator and prelate Tommaso Inghirami. He’s pictured at his desk, garbed almost entirely in red, in a typical pose of contemplation, gazing upwards, but look closely at his right eye and you will notice something amiss: there is too much white, as if his eyeball were a shelled egg, its minute pupil dabbed as an afterthought. Inghirami lived with strabismus – a misalignment of the eyes, possibly caused by his fall from a mule – and his right eye is almost turned to look behind him, lizard-like. Were one to trace his gaze from those two eyes, extending outwards to see where he was looking, you would draw two lines into infinity, lines that would never cross. Inghirami saw two things at once.

I had not heard of Inghirami and his misaligned eyes until I fell backwards – not from a mule, but in a skiing accident several years ago, cracking the back of my skull against the compact winter ice of a Vermont resort. I had played rugby until the age of 16, and knew how it felt to have a knee or elbow to the head, but this blow possessed its own character: unsettling, strange and electric. I remember thinking, as I got up from that icy slope, that this fall would exact some price, though back then I did not know its currency.