Eye movement mystery

My girlfriend’s therapist has here doing a therapy called EMDR. Basically it consist of someone moving their finger back and forth in front of your face, which you follow with your EYES only, apparently to alternately stimulate each lobe of your brain.
I was fooling around with this, decided moving my own finger queered the experience, so I figured I would stare at a fixed point and move my HEAD from side to side.
And in the course of playing around with this I found to my surprise that I couldn’t move my eyes from side to side as fast as I could move my head from side to side and remain focused on a specific point.
Aren’t the same muscles (excluding the neck, of course) involved? If so, then why does this phenomenon occur?

I don’t know about that, but your girlfriend should find a different therapist. See Mental Help: Procedures to Avoid at http://www.quackwatch.com . EDMR is described on the same page with Facilitated Communication, Past Life Therapy, and Thought Field Therapy.

doesn’t help me, but hopefully it will her. thanks.

So you’re sitting in front of a piece of paper, shaking your head and trying to keep your eyes focused on the paper? I just tried it and indeed I can’t maintain focus. In my case it’s because my glasses introduce distortion. When I move my head I’m looking through the different part of the lens and the distortion is different (much larger).

If you don’t wear glasses, I don’t know why. I’d guess that when the eyeballs move, the surrounding muscles and tissue distort the eyeball and it takes some time to compensate (i.e. re-focus).

I wonder if this is at all related to continuous tracking. You know, I turn my head but keep eyes steady; smooth eye movement. I try to sweep my eyes to and fro; herky-jerky eye movement.

creepy, huh…
jb

Is the fixed point that you’re staring at the same distance from your eyes as your finger was? Distance makes a big difference.

Even if you were sitting in front of a wall wjich was built so that every point was the same distance from your eyes, I have a feeling that you still couldn’t track smoothly, even if there were a grid up or something.

Seems that focusing is the primary job of the eyes. After that’s done, all else can continue. But apparently the eye has to focus on something.

Which is weird, cuz your eye muscles can track smoothly by themselves. I guess it’s like crossing your eyes outwards; physiologically possible, but damn hard to do.

jb

See…
Slight hijack of my OWN thread…
My uncle could cross his eyes outward. Thats really creepy. BTW IIRC that is called ‘walleyed’.

Chronos, wanna take a whack at this?

The jerking motion that your eyeballs make when you follow something with your eyes (like reading a line of text) is called a saccade. Saccades occur even when you are looking at a stationary object, but in a smaller range of motion according to this bizarre Christian opthamology site I checked. (Enter only if you are equipped with several grains of salt- I know there are better cites, but this is the first one that came up by searching for “eye jerks” :smiley: ) My guess is that when you move your head instead of your eyes, the smaller saccades are involved- so they seem imperceptible compared to what you feel when you track something with eyes only.

I’m not sure why you invoked my specifically, warmgum (dammit, Jim, I’m a physicist, not an optamologist!), but I’ve always been able to slighty “wall” my eyes. In fact, it was only in the past few years that I learned to cross them (but now that I know how, I can cross them further than I can wall).