Well, that was... inconclusive. Saw the eye doctor today, and he said that their scans showed nothing untoward. Eye and retinal health is good. There ARE a couple of small spots on the right retina, and one on the left. First point of investigation is blood pressure (will check at home tonight, but has consistently been "high normal"), cholesterol (which is almost certain to be high) and diabetes, as all can cause that type of defect. Least likely is a leaking blood vessel, but given my general eye health is good, vision is good, and the ongoing pandemic, a dye test is unlikely to be a priority. He'll write to my GP and I'll call and get the tests arranged, and I've a follow up appointment in three months with him.