Your dog's symptoms donot seem to be associated with the incident of the trap and the rat.
I am in the Bay Area too (Saratoga) I would suggest that you consult with Deborah S. Friedman, D.V.M., Veterinary Ophthalmology, of the Animal Eye Care, in Fremont, especially if you do not have a vet. It is important to have this eye lesion checked in order to receive an accurate diagnosis and treatment as deemed appropriate.
There are several considerations. Your dog could have Ectopic Cilia, which is an abnormal eyelash that grows through the conjunctiva and is usually very painful and almost always causes an ulcer. This may also be Distichiasis which is an abnormal position of eyelashes on a lid margin that result in irritation of the eye.
IWhat type of breed is this? In regard to your dogs fur, does he seem to be continually scratching and licking? Do you use Frontline or Advantix for flea control?
Is the skin simply red or do you see bites or sores? If you can provide me with more details, I will be better able to provide you with further assistance.
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