Charlie and George are growing at an insane rate. Here’s a photo taken about four weeks ago. And another taken ten days ago:
And they’ve grown a lot since then. When Charlie first came home from his operation he was 3.5 lbs. I’m guessing he’s close to 5 now, but George is far bigger and heavier, more like a young cat. Charlie, though smaller, still gets his preferred perch—the highest level on the condo; George mostly likes to hang out on the third, shaded and sheltered by the second where, when he’s bored, he can grab at Charlie’s tail and chew.
Charlie is still a kitten, still fearless, and still visually impaired–still a nightmare combination for kitty wranglers of a jumpy disposition. But you’ll note I no longer say blind. Neuro-plasticity is an amazing thing, and Charlie’s brain has been frantically rewiring. He can definitely see some things. Equally definitely, he can’t see others. And, most confusingly, that seems to be variable. At first I though the variability might be related to non-visual compensation: being able to sense the movement of air when the feather passes closely enough, or fast enough; or perhaps he can hear it; or smell it. But through experimentation—which both he and George thoroughly enjoy; they’re getting hours of focused play a day—I’ve determined that this is not the case. I think sometimes his brain just sort of fritzes.
On top of that, some part of his visual field is missing. I’ve been researching acquired brain injury and visual impairment and suspect he has some kind of hemi- or quadrantanopia (or -anopsia). There are all kinds of variants. Perhaps the left visual field of both eyes is missing, or maybe part of the right visual field that is, homonymous hemianopia. Or the centre, or the outside (heteronymous hemianopia). I’ve been trying to work out ways to test that.
The games/tests I’ve been using are tracking/chasing games. Sometimes a cursor against a white screen, or a red laser dot on a pale carpet (neither of which he can feel or smell or hear); sometimes Feather (bunch of feather at the end of a line), and sometimes dropping a variety of things from a height.
The first time I tried the laser pointer on the carpet, he lost the red dot about 70% of the time and took a lot of patient tempting to reacquire it. This video was taken about ten days ago:
You can see the difference between Charlie, who doesn’t seem sure he’s really seeing the dot at first, and George, who’s all Kill! But Charlie is improving rapidly. And this morning he did not lose it once at normal twist-and-turn speed, but did lose it when I flicked it away suddenly. And it no longer takes him long to reacquire it. George, on the other hand, can follow it almost anywhere, at any speed, and he reacquires almost instantly.
In terms of the cursor, well, see for yourself: he seems to track left more easily than he tracks right. What does this mean? I’m not sure.
He might be missing some of his right visual field. But that’s not the only problem. Chasing Feather gives a more interesting, 3-dimensional view of what he can and can’t do (though of course complicated by compensatory sound/touch etc.). Here’s a video taken about a week ago of Charlie chasing Feather.
As you can see, most of the time his coordination is fabulous, and then sometimes it goes to pieces. And he can’t seem to see things right in front of him. So I thought: binasal hemianopia, that is, the middle is missing.
There again, one test he fails consistently is seeing/tracking an object falling from a height, whether it’s his white miniature soccer ball, one of my juggling bags, or a piece of white cottonwool. So it could be that he simply can’t process at speed, or perhaps that an upper part of his visual field is missing—maybe heteronymous quadrantanopia. Apparently, while occasionally those with this damage can recover, it’s not massively likely:
The prospects of recovering vision in the affected field are bleak. Occasionally, patients will spontaneously recover vision in the affected field within the first three months after the brain injury; however, vision loss remaining after this period of spontaneous recovery is traditionally thought to be permanent
It’s now been about five weeks since Charlie’s brain injury. So there is a faint possibility of recovery but unlikely. The goal now is adaptation. I have mixed feelings about this. On the one hand, I’d feel much happier about the possibility of letting Charlie outside occasionally if his vision were wholly intact. Right now, I don’t think he’d see a barred owl swooping in to snatch him away. On the other hand, he has a wonderful time indoors and sees everything he needs for a full life, and indoor-only cats do tend to live longer. So we’ll just see how well he adapts with constant training-as-playtime. I suspect he’ll be happy either way.
At this point, though, my main suspicion is that I’m not training Charlie and George, they are training me: hours and hours of play time a day, plus treatsies for playing, and endless comfy lap time afterwards. Oh, well. I’m getting a lot of reading done.
In a few days I’ll do another post, this time about all the non-vision-related adventures of Charlie Kitling and Master George. There are many. Meanwhile, catch up on previous kitten reports here.