Brain swelling or surgery would not cause the eyelids to swell.
This is most likely either:
infection of the eyelids and lashes.
Often it is viral infection, but if antibiotics helped, for whatever reason he is getting a blepharitis. Infection of the lids.
If it is not the lids, and is the other thing you describe, then, it is more likely:
He needs to figure out his exposures, if his immune system is suppressed, which is likely, and talk to his doctor about a cream or drop he can use in the eye.
He needs to have his kidney function checked, also thyroid testing, and an EKG
OK, let me know if you have more questions.
Also, please click a positive rating on the rating scale. [This must be done manually at the top of the page]. In fact, a 5 rating squares me with just answer and allows me to provide prompt and accurate service to you, but does not increase your cost. And, I will be here for any follow up needed