Just noticed these comments and although I dont have answer/s I have had eye issues for many years, culminating in narrow angle glaucoma, but also had bowel issues, thyroid (hypothyroidism); off work due to red sore eyes at work, turned out many years later to be no filter on xerox machine outside my office and i suffered so much with burning eyes for years!

Also some plants indoors and outside... have photo of a wild plant in garden that has latex in stem and got some painful blistering skin when rubbed eye and can post - its a wonder I didnt lose vision; eyes so dry could not open them through night; optometrist and dentist wanted me checked for (spelling?) Sjojerns but my family dr refused saying: you dont have it!

Shopping in dept. stores and so many chemicals and such , eyes burned and were red, but lasted after left store.... and am sure have missed some things/places that burned my eyes but not to my knowledge or recollection food of any kind.

Just thought would mention its horrible , like having soap in eyes yet, as you say, optometrist found no cause. Someone mentioned detergent and recently I hadn't realized I had bought extra concentrated laundry soap, washed and changed sheets put back on bed, and all night eyes red and sore again, and realized linens not rinsed properly from too much detergent, so just rewashed them with NO detergent just plain water.. what stuffing is in your pillows . ... its is very hard on the nerves too trying to find out what causes this: do you wear glasses and use a spray to clean them? Using any cleaning products in your home that are eye irritants? Maybe read side effects of ANY medications you are using, even medicated creams, shampoos to see if affect eyes.. I was amazed at how many affect some people's eyes!! I gave up on reading books from library as I think may be sprayed or wiped with disinfectant... it makes one suspicious of just about everything!

I now use dry eye drops with no preservative and drops for glaucoma which have other side effects unfortunately, and although my eyes are much better than they had been for years, still feel sore once in a while.... wish I could tell you a cure or solution and you are not only ones going through this and hopefully - keep searching and as someone suggested keep diary and maybe will find cause... wishing you the best. Hope my experience might shed some light on a cause and you will get some relief sooner rather than later.