A question without clear answers, still... It is very important to understand this. Photophobia is a major symptom of dry eye and therefore your etiology needs to be carefully studied to obtain solutions. I think the dry eye causes photophobia by the increased sensitivity to light of the nervous ocular surface. This increased sensitivity in turn can be caused by friction of the lids on the ocular surface. Maybe the tear also functions as a bandage, regulating over-stimulation. I also still think that the decrease in tear may allow greater passage of light to the retina, sensitizing it.