The "lump" appears to represent a severe conjunctivitis/dacryocystitis (infection of the lacrimal apparatus) which may have abscessed under the inferior eyelid. I can rule out a tumor because the area normalized when a systemic antibiotic was initiated. Have Hedwig's vet culture the eye this time around so you'll know which infectious agents are present and the very best of the antibiotics to give him. Thank you for the good photos! Please respond with further questions or concerns if you wish.
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