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Comment by adolgert | Hacker News Reader

It was relatively common in the CAVE to have someone see in stereo for the first time. The shutter glasses have LCDs that are synchronized to flip black and then clear, alternating eyes. The projectors are synchronized to this flip so they show the correct projection for the correct eye. This technique sometimes defeats eye dominance problems that impair stereoscopic vision. Because stereoscopic vision accounts for only about 30% of our ability to judge distance, behind occlusion and motion parallax, it was amusing but not life changing.

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That lines up with my experience. The alternating esotropia means that at any time one of my eyes acts as dominant, but it will change based on which direction I look and is also under voluntary control.

I have played ultimate frisbee for years quite successfully, and people were usually surprised when I mentioned I have no depth perception. I've met another A.E. person who was a good softball player. The hard part is when I have to look up at blue sky to catch something; the size difference between "can jump to catch it and cannot" is not very big, and there are no parallax/overlapping cues to draw on.

Interestingly, one friend said "Oh, that explains it" when he learned about my eyes. He noticed that I never look into a cup or glass straight-on when filling it, but instead look at it from the side so I can see how full it is. The growth of the circle of the top-of-liquid is small enough that I will heavily underfill a glass rather than risk spilling. As you suggest, it's not deep life-changing stuff, but it is quite a novelty!

This is exactly the sensation I get with stereo vision. I was told that I'd had a lazy eye from the age of 2 or 3. No one ever gave me details other than that, and I always believed this shifting-dominant-eye effect was a result of the lazy eye. It may be related, but I never found out about the effect by researching lazy eye, aka amblyopia.

How did you come to learn about esotropia? It sounds like the doctor might have actually diagnosed me with that, as I distinctly recall having to wear a patch very early on in life.

Ánd finally, thanks for elucidating on the name of the condition and how you're affected by it. It spot on describes my experience and I'm glad to know a bit more about myself.

The esotropia was diagnosed when I was a kid. In fact, the "visual specialist" I visited as an adult was actually a pediatric doctor, because they're the ones who have the most experience with esotropias. I don't have any memory of being diagnosed with it; it happened when I was 3 or 4, I believe. My left eye is also mildly dominant; if I'm looking straight ahead it will tend to win control. When it was diagnosed, they did an eye surgery to correct the tracking of the off-eye, and they tried to get me to wear glasses to further battle against eye-dominance, though I was a reluctant participant in that experience.

I learned the alternating esotropia name from my parents, probably during high school or so. I don't think I was able to name it before that, and I don't remember the context in which they shared it. Probably I was complaining about the stereograms that were popular at the time; I have never been able to see anything in those.

Aside from what I've mentioned so far, I also get a free bonus of driving my wife a little crazy; she always tries to figure out which of my eyes I'm looking out of when we're talking face-to-face. It's nice to have a bit of novelty that is, all-in-all, not really that big of a deal. It's fun to talk about, though, as evidenced by the popularity of this thread.

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