I have been vegetarian and vegan for years.  I have better eye outcomes when I eat vegan and many vegetables, limit oils and fat, and maintain a lower weight.  Unfortunately for me, the cookies and ice cream and french fries version of the vegan or vegetarian diet doesn't help me much.  A study might want to have a qualitative component, since it is quite easy to be a "junk food vegetarian".  My retinologist noticed a difference with the lowfat vegan diet (unprompted, he said, "keep doing whatever you are doing".) Did I?  No (with lousy results), but maybe I will now. This is interesting.