What is the cause of the eyelid swelling in my client, and is there anything further we can do to help?

This is karmic in nature. It is being recreated by the body to mimic a bodily response to injury in a parallel lifetime that has been stirred up by spirit manipulation to cause inner fear and concern, and the body, seeing the dilemma, has been taking it to heart and recreating the consequence of what was suffered previously, at least to the extent it can, but this is a visibly noticeable alteration that is troubling and unwanted and needs healing. There is healing underway because the karmic issues are being addressed with the Protocol work that was set in motion, but because this symptom is being created largely by cellular memory, it will take some time for the body to relearn its lessons and get the message "this state of affairs is no longer needed," and it can stand down and cease producing the symptom. This will fade over time if it is ignored. So not giving it conscious focus and worried concern would avoid signaling the body "this is important and needs to keep going," while the healing as well will be working on the karmic underpinnings to prevent reconnecting to the akashic records of the original trauma. So the two will work together to turn the tide here given enough time and patience.