My vision research these days focuses on depth perception and motion perception in two disordered populations: people with albinism and people with infantile strabismus. (Actually, that’s not quite accurate. I’m doing some exciting stuff on motion perception in normals, but as I update my web site, it’s getting late, and I just don’t have the strength to describe that research. Stay tuned.)

As for albinism, in addition to the causing the obvious pigment abnormality, it also causes a dramatic misrouting of the optic nerve: In normals, each cerebral hemisphere’s visual cortex depicts the contralateral side of the visual field, but in albinos, each cerebral hemisphere’s visual cortex depicts the entirety of the contraleteral eye’s visual field. Thus, whereas normals’ early visual cortex is chock full of neurons responsive to binocular input, albinos’ early visual cortex is largely bereft of such neurons. This might be expected to disrupt binocular vision in albinos, and indeed it does. However, albinism can spare a surprising amount of binocular function. My research investigates how much is spared, and begins to offer speculations on why.

As for infantile strabismus (crossed eyes or uncrossed eyes with onset early in life), the lack of eyes pointing the same direction has obvious implications for binocular vision. In fact, if the eyes aren’t aligned during a critical period in infancy, binocular vision never develops normally, even if the eyes are later aligned surgically. In addition, motion perception is disrupted. In early infancy, it is normal for each eye to have a slight bias to perceive nasalward motion better than temporalward motion. That is, the right eye is more sensitive to right-to-left motion than to left-to-right motion, and the left eye is more sensitive to left-to-right motion than to right-to-left motion. If the eyes are properly aligned during the aforementioned critical period, then these asymmetries disappear as the infant develops. However, if the eyes aren’t properly aligned during the critical period, then the asymmetries can persist into adulthood. This is probably related to the fact that subjects with infantile strabismus often have latent nystagmus, whereby when viewing monocularly, their eyes tend to move slowly nasalward, then snap back temporalward to begin a new cycle of nasalward motion. It is as if the eye were responding to a world moving nasalward, even when it’s at rest, on average. I am investigating the extent to which various visual functions are preserved in subjects with infantile strabismus, in order to try to pin down which parts of the visual system are impacted by the infantile misalignment, and which parts are spared.

And, yes, that is a picture of my eye (one of them, anyways). (Want to see a a student’s conception of what my whole head looks like?)