I think it all depends on the individual horses personality whether they are messy or not.
I read in Equus Magazine that it takes 45 minutes for a horse's eyes to adjust to a change in light, whereas it takes people about 3 minutes to adjust. The article was about taking horses into indoor arenas where there is low level lighting. The riders need to be more aware that the horses' eyes have not adjusted. If this is true, I can see why you would hate lights shining and blinding the more sensitive horses.My mom always shines a flashlight into a dark trailer for the horses to “see,” and since General it annoys the crap out of me. Lol
I can see Queen is going to hate lights too.