Remove the bullet from my cats head

This is Variks.  Up until yesterday, a long, hard start on life seemed to have been put behind him, and things were starting to look pretty normal. Unfortunately, nearly three years ago, someone shot my cat in the head. 

We only just found out.

He started life in a feral cat colony and ended up in the care of a local shelter before his first birthday. An allergy to fleas made a bad infestation that much worse, and the additional parasites they brought with them didn't help. He was just finishing up his treatment for what seemed to be a stubborn sinus infection when he was cleared for adoption. 

We were looking for a cat to keep me company while I sought treatment for PTSD and Depression. He headbutt me in the face, full-force, to introduce himself. He loved all the staff at the shelter. He loved other cats, and loved dogs about as much. He was in love with the world and I fell in love with him for it.

That was 2 years ago, and for all of the love he has shown humans, he's been silently hiding what humans have done to him. His name in the shelter was Steel, and now we all know that he's made out of it. 

Yesterday morning, his right eye started swelling shut. He was depressed and for the first time in his life, irritable. His pupils we're having issues dilating, he seemed off balance and weak, and we knew something was wrong.

We took him in for an emergency visit, and finally performed the X-ray that shed light on years of head-scratching health issues: There has been an air rifle pellet lodged in his skull, causing minimal damage and irritation until it migrated to just the right place to be a problem. Where exactly that place is, we do not quite know yet, but it's putting pressure on his optic nerve, causing a lot of obvious pain and issues with this eyes. This is the first challenge we face together, and we need your help. 

The X-rays aren't giving us a good idea on where in his head the pellet is. Without its exact location, we can't plot out a surgery to remove it. For a clearer picture, we need a CAT scan. (I know, right?).

I'm hoping that starting with this amount will help us secure a CAT scan so that we can map out the location of the pellet, and once we know where it is and how it entered, we can start shopping for a specialist to tackle an obviously delicate, complicated, possibly risky, and guaranteed expensive surgery. There's no price sheet for surgeries like this, so we have no clue what it's going to cost to get this thing out of there. I just know it's worth it. We're at ~$180 for the X-rays and meds today, but we know this is hardly the beginning. 

We're fighting against time and swelling at this point. He's stable, he's on anti-inflammatory medication, but with how quickly the issues kicked in, we don't know how much time we have before things degrade. The past few years were apparently on borrowed time, so these next few days are critical. We have to act now. 

This guy has made the world a much less scary place for me, and I owe it to him to try as hard as I can to find someone willing and capable to rightly undo what has been unjustly done to him.  Can you please help?