Thanks for the reply.
Cataract did occur to me as well. The opthalmologist who arrived those figures at the time said both eyes were very clear so I presumed that he could see no trace of a cataract. He just said "Well you're 50 now". The lateral thinking idea has drawn a blank as well. I'll see how it goes.... not necessarily for licensing - the best I can hope for nowadays is an NPPL grade solo/safety pilot!
Hanna.