From The Optical Shop

And the theme today is circles: a circular window with a view of the bay (which, as you may be aware, is broadly circular), machines with circular eyepieces or half-circular chin-rests, such as the one on the right, which provides a visual field test: with a (circular) eyepatch over one eye you stare at the orange dot and click a switch when you notice any peripheral flashes. Caoimhghin was informative, chatty and solicitous as he manipulated the various bits of kit. I felt the way one might while undergoing a palm-reading (if one put any store in such things). I am superstitious enough to never allow a stranger peer into my hand's broken cat's cradles, but I do put store in those who can read the lines in my eyes. And the story seems happy enough so far, apart from some slight astigmatism and the need to have one of my glasses' lens replaced.