SUMMARY: She's getting older. Sigh.My regular vet also found nothing out of the ordinary with Tika--for older dogs, that is. She has a slight heart murmur, typical of older dogs and probably wouldn't cause problems. (Another vet a couple of months ago mentioned the murmur but I forgot all about it until yesterday.) Her hips have some arthritis, which is completely normal but might not explain the things I noticed.
(Of course, arthritis/weakness/pain in her hips could cause some of the same issues--caution in curved tunnels, on dogwalk... but you'd think jumping would be equally affected. Dunno.)
He said he agrees that the nuclear sclerosis could very well get the results I'm seeing. Combining both vets' descriptions: Dogs tend to be far-sighted to begin with, so never see things up close as well as we do. This hardening of the lens makes them even more far-sighted. In other words, close-up things are probably a bit blurry to begin with, and get blurrier as the lenses harden. From the opth's generic text: "[In extreme age, it] can become so dense that it makes it difficult to judge distances, or the patient might want more light to navigate."
So a weave pole right in front of them or the inside of a dark tunnel or the narrow width of a dogwalk might be harder for them to comfortably view. But jumping, out in broad daylight--jumps are far enough away as they approach them rapidly that a dog who's already very familiar with jumping might have no problem at all. At the moment, she seems fine in everyday low-light situations, but I'm really wondering about those dark tunnels. She still blasts through my lighter-colored tunnels at home.
And, oh, BTW, it makes her eyes look someone blue and cloudy, similar to what one might see in glaucoma or cataracts, which is why (when I started thinking about it) Tika's eyes looked cloudy to me. But it's not nearly as bad as those other things.
This is all good news compared to what it might have been, but maybe bad news for agility. Certainly bad news for my silly human fantasies of blue ribbons or continued top ten work.
My comments about her being so much slower than normal last weekend? For example, her clean Grand Prix was the 6th slowest, at 4.05 yps, out of 65 for which I have data for her. Of the 14 slowest runs, the others either have runouts (ran past an obstacle and had to go back for it) or say "holding on contacts." From there on up, they range from 4.20 to 5.1 yps (with a sprinkling of recent ones in the upper ranges and a sprinkling of younger runs in the lower ranges). So, yeah, she has been slowing down gradually, but that was a big drop last weekend.
Tika also has a melanocytoma in her right iris. It's a benign pigmented growth--basically like a mole, the opth. said. It's not impinging on her vision at this time and doesn't pose a danger. Just something else to keep an eye on (so to speak) if it starts getting larger.