The condition you describe sounds like idiopathic non-inflammatory leukoderma (there seem to be various names for this condition). The closest equivalent condition in human terms is vitiligo.
I know of a part-Arabian who had this condition and lived to a ripe old age. The skin around his eyes was pinky white and I remember that the shape of the pale skin area changed somewhat over time.
Vitiligo can affect any area of the horse’s body that is thinly haired. There is no treatment that I know of. So what you are seeing is probably only a cosmetic condition and not harmful to the horse.
If however, you are at all concerned or there appears to be tearing, swelling, cloudiness or other unusual symptoms in the eye or eye area I would recommend you call a veterinarian. Never take a 'wait and see' attitude with eye infections or injuries.
