floatergasted, good luck with the Pea Aubergines.
Although your father has a fine vision, he could have their vitreous detached, because "is a common condition which occurs in about 75 per cent of people over the age of 65".
"Many people are not aware that they have developed PVD but some notice symptoms such as floaters or flashing lights. Floaters can take many forms from little dots, circles, lines, to clouds or cobwebs. Sometimes people experience one large floater which can be distracting and make things difficult to read" as you can read here:
http://www.rnib.org.uk/xpedio/groups/public/documents/publicwebsite/public_rnib003660.hcsp

The PVD seems to be a natural protection of the body, because at the 80's it seems than more of the 50% of the vitreous is liquefied. So, we can understand that a PVD is good after some age... and it start to be ussual in the 40's or less in myopian people.

I'm not going to say that fruit is not good for floaters, but we have to think all possibilities, and in the case of your father has also the possibility that the floaters dissapeared by a PVD.