Levels of Perception is a marvelous book co-edited by Laurence Harris and Michael Jenkin, based on a Festschrift for Professor Ian Howard held in 2001, 12 years prior to his death on June 1, 2013 at the age of 85. In an essay written for the Journal of Behavioral Optometry, I referenced my interaction with Ian during Demo Night at the G. Wiz Science Center as part of the Vision Sciences Society Meeting in 2007. At that meeting, Ian was displaying a two-volume set he had self-published on Seeing in Depth, and I was so captivated by it I begged him to be able to part with his last set which I devoured on the plane on the way home. Publication of Seeing in Depth was taken over by Oxford in 2008, but I treasure my set published by Ian because of the personal connection. But I diverge … There are many favorite chapters I have in Levels of Perception, one of them being Plasticity of the Near Response by our old buddy from U.C. Berkeley optometry, Clifton Schor, O.D., Ph.D. I’ll never forget when Clif came to a COVD annual meeting many moons ago, and gave an elegant lecture on the derivation of why +0.50 lenses often proved to be the ideal lens for nearpoint tasks.
Most developmental//behavioral optometrists are well-acquainted with Skeffington’s notion about essential degrees of freedom between accommodation and convergence. Schor’s introduction to plasticity of the near response notes that disparity vergence as related to binocular eye alignment can be described with three degrees of freedom, including horizontal, vertical, and cycle components. All three components of disparity are necessary to interpret space as by themselves, horizontal, vertical, and cyclo disparities are ambiguous. These disparities are disambiguated with information about distance and direction of objects relative to the head. In essence, binocular alignment is achieved and maintained by matching the innervation for horizontal, vertical, and cyclovergence to the physical constraints set by the EOMs and orbital connective tissues. Calibration occurs through neuromuscular interfaces including tendon and pulley systems that help coordinate these three degrees of freedom within the vergence resting state and response interactions.
We’re used to thinking of postmodernism in terms of global movements, and a chapter in Levels of Perception co-authored by Harris, Beykirch and Fetter entitled Levels of Analysis of the Vestibulo-Ocular Reflex: A Postmodern Approach puts a nice spin on this. The VOR is an amazingly flexible system that has come to be regarded as a context-dependent motor response with extraordinary adaptive ability. The VOR is able to adjust to a remarkable array of demands that are placed on it by virtue of the position of the two eyes in the head – a global constraint of a different kind – and the geometry of their relationship to objects in the outside world. Bear in mind that the directional pull of the EOMs as three yoked pairs in each eye are arranged in three planes roughly aligning with the orientation of the semicircular canal planes: horizontal, vertical and oblique.
What’s the connection to postmodernism? The clue is the postmodern movement in architecture emphasizing context, which now pervades many aspects of knowledge. In a postmodern world actions and thoughts can only be interpreted as part of the total environment in which they occur. Even the couplings between semicircular canal stimulation and which EOMs are activated are flexible.
Albert Sutton is one of the pioneers in developmental/behavioral optometry, and he anticipated postmodernism in terms of context dependency of the VOR. That is what I believe to lie at the core of his notion that each person, from infancy, builds his own visual space world. Like so many of our pioneers, Al was well ahead of his time. Vision science is now catching up to his ideas that visual space, and the neurology that supports it, is very much context dependent. Do yourself a favor and get a hold of Al’s seminal works available as volume 1 and volume 2 from OEPF. I wish that I could call or visit Al to celebrate his ideas. We should have had a Festschrift for him of the nature that Harris and Jenken coordinated for Professor Ian Howard. So this will be my little tribute, to a lost role model, from Paul Simon’s lyrics to You Can Call Me Al: “He looks around, around … He sees angels in the architecture, spinning in infinity …” Our space world is partly embodied in the pitch, roll and yaw of the VOR, Al, as choreographed by Paul and Chevy at the 2:18 mark of their video: