Test for Celiac's disease...sorry. Celiac's.
Go to a Naturopathic Doctor. You need a health coach for this.
Could be celiac's, chron's, coliitis, parasites, mycoplasma infection, general food intolerances, leaky gut syndrome, ibs, candida, gut dysbiosis and any other digestive and gastrointestinal condition or combination of conditions.
There are over 80 different causes, sometimes very difficult to dx
You need to do the hypoallergenic or elimination diet first and gradually build up your intestinal flora safely at well as your immunity!
So you need a combination of traditional medicine for many tests (blood work and scans) and Naturopathic medicine for holistic treatment.
Vision issues could be related to neurological issues connected to low nutrient assimilation and/or metabolic dysfunction (usually carbohydrates).
Try eliminating carbs and dairy totally for the next little while and see what happens.
That means no grains,sugars,starches,sweets and sugars,sodas,cereals,
pastas,breads,potatoes etc. Hard to do, but tough it out if you can.
Look into GAPS and SCD programs. Just do a search.
Extra virgin coconut oil up to 4T daily is very helpful. Start with 2T daily
for week 1. More info @ the coconut research center website.
Hope this helps,