It just clicked: I can now see the polarisation of light with my naked eyes! It's quite strange as I'd noticed the effect before but didn't know what it was. Now I can easily see the "brushes" caused by the polarisation of the light interacting with the dichroic pigments of the retina. It's quite surprising, like finding another sense you never knew you had. For those who haven't experienced it, try to find a polarising filter (or any piece of polarised glass or plastic) and look through it at a polarised object like an LCD monitor, or the sky will do. Rotating the filter should cause the brushes, which appear as faint blue and yellow blooms in the centre of your vision, to rotate. Now that I know what they look like I can see them without even needing a filter.
I forgot to mention in my last entry that I'd sent my titanium ring to New Zealand, back to where it was made, for resizing. It had always been slightly too large so I decided to have it taken down one size. It returned the day before my birthday and it's now a perfect fit! Resizing titanium rings is usually considered impossible by most jewellers (titanium can't be cut and rejoined like gold and other soft metals can be, and the process of heating the ring to temperatures sufficient to do anything with it also cause the surface to oxidise and turn blue or purple). I have no idea how Artifact did it, but they described it as "shrinking". They also gave the ring a clean and it looks as perfect as the day I received it last year!