Double Vision

I think the root cause of my main vision problems is ophthalmoparesis (sluggishness and weakness of the eye muscles via loss of muscular control via degradation of the cerebellum) caused by having SCA3, and I know my vision problems are not fixable. In 2013 at age 45, I made a concerted effort to improve my vision, involving an ophthalmologist and two optometrists. My two main problems are:

  • I can’t look quickly from one place to another. This is vestibulo-ocular areflexia. (Not improvable.)
  • Double vision. When I look straight ahead, I have 20/20 vision (with glasses). Vertical head tilt is mostly not problematic. If I rotate my head the slightest bit horizontally, I see double. The more I rotate my head, the worse it is. (Improvable? That was the question.)

What I learned is this:

The kind ocular muscle degeneration I have is symmetrical. It allows me to have 20/20 vision when my side-to-side ocular muscles are relaxed and I’m looking straight ahead. This turns out to be a mixed blessing. Since any vision correction (in lenses) is fixed, but the degree of double vision I experience is variable, there’s nothing I can do except be happy that I can see straight ahead.

When ocular muscle degeneration is asymmetrical, the eyes are out of alignment and each looks in a different place even when trying to look straight ahead. This is called strabismus (usually esotropic [crossed] or exotropic [divergent]), and I don’t have strabismus even after more than 10 years of SCA3-induced vision problems. Furthermore, many (most?) people with SCA and strabismus do not experience varying changes in their vision as they rotate their heads. Prism correction and strabismus surgery are options for them but not for me.

Wearing an eye patch will eliminate double vision. My fear is that asymmetrical usage of the eyes could cause strabismus. I was informed otherwise by an ophthalmologist, but I’m not sure that the answer I got was definitive. Still, I have used an eye patch now for two years.

I didn’t want to wear an eye patch in public, but I wanted to know if it would help, so I pursued getting an opaque contact lens that I could wear discreetly. Yes, such contact lenses are readily available, and many optometrists will work with you to get them (not all will!). Ultimately, I had little success with this approach, and here’s why:

Opaque contact lens

The brain combines image data from both eyes, and you see one image. If you’re getting good data from both eyes, the combination gives you depth perception. When you put an opaque contact lens in one eye, there’s no way to prevent some ambient light from still getting into that eye. As long as your eye is taking in light, your brain will combine that pure light with the good eye’s image, and the result is a washed out image. You can poorly simulate this by shining a flashlight directly into one of your eyes. Does your brain shut off that eye? Of course not.

In public with the lens in place, especially with strong ambient light, one eye provided image data and the other eye provided only bright light, and I felt almost completely blind.

You might wonder: when you close one eye, why doesn’t your brain combine the good image of the other eye with the complete darkness of the closed eye? I can only guess that when you close an eye, your brain essentially gets no data from that eye rather than treating it as darkness and combining that with the good eye.

Putting an eye patch over the eye containing the opaque contact lens (or closing the eye) was an improvement too great to justify using the contact lens at all. The patch was better, easier to use, and 100 times cheaper. Getting the single, disposable contact lens cost USD 425.

The bottom lines:

  • Reasonably healthy eyes are ignored by the brain only if they are closed.
  • An eye patch will block more light than an opaque contact lens.
  • Closing one eye is physically awkward and tiring.

The eye patch wins

Note that I had stopped driving already for a year because of my vision problems. I was looking for improvements while reading and playing the piano. I ended up wearing an eye patch (indoors) every day for about six months. I wear it less now, mainly because I care less about my continuously worsening vision and have come to accept that it is bad.

Also, wearing an eye patch reduces visual input by 50% in addition to eliminating depth perception. It causes a distinct one-sided, asymmetrical feeling, which makes moving around with ataxia even harder. It adversely affects proprioception, i.e., knowing where the parts of my body are with respect to the rest of the world. See here for why that matters.

The path to worseness

With ataxia, things always get worse. So, how does double vision get worse?

Because my eyes do not stay spaced to properly combine into one 3D image, my brain feels like it has two choices of what to look at. When I try to focus quickly on something, my brain can’t decide what to do. It tries one eye and then the other; it jumps back and forth. If I’m lucky, the jumping settles down in a few seconds. If not, I close one eye to stop the jumping. This jumping used to never occur, but now it occurs quite frequently. That is, I see this as my double vision worsening. Again, I stopped driving in 2012 at age 45 because of this.

This jumping is easily mistaken for nystagmus and in fact may lead to it; I don’t know. Many with ataxia say they have nystagmus. This is one of the frustrating aspects of having a rare disease that takes years, even decades, for symptoms to mature and finally match the tiny status quo.

Now, my eyes are getting jumpy because double vision gives me a choice of what to look at, so my eyes jump around and my brain tries and fails to come up with a single 3D image. I will begin calling this nystagmus when my eyes get jumpy for no reason, and I can no longer keep them steady.

Oscillopsia? Strabismus? Again, many with ataxia say they have one or the other or both, but so far the descriptions don’t match my experiences.

I continue to assume that the only condition caused by my cerebellar degeneration is ophthalmoparesis, leading to double vision, and that makes my eyes jump as my brain tries—and fails—to focus my eyes. It’s not my eyes jumping that causes vision impairment; the impairment comes first, and the jumpy eyes comes from that.