Consultant doctor here (not an ophthalmologist).
As others have said, the language used can make things sound different. I was a junior doctor for 13 years. I was a junior doctor the day before I started my first consultant job, despite having all that experience and postgraduate exams passed years before.
When the junior doctors' strike in 2016 happened, my consultant colleague posted about how when she needed an emergency C section, the registrar (so the same level of doctor that is being talked about in the OP) made the correct decision that the C section was needed, and got her baby out and safe before the consultant could arrive and get changed/scrubbed for theatre - and he only came because the patient was another consultant!
Resident doctors (who used to be called junior doctors) are running hospitals overnight, dealing with cardiac arrests, operating on emergency cases, giving anaesthetics, doing invasive procedures such as lumbar punctures on tiny babies. They have been given gradual exposure to procedures/complex cases as they have become more senior. I'm not a surgeon, but when I was in my first year after qualification doing a surgical job, we sometimes assisted at operations - this meant that we might have started off holding a piece of equipment to keep the surgeon's view clear, but you might also be asked to put in stitches at the end. For a surgical trainee (meaning a fully qualified dr, in a training programme to become a consultant where their progress and experience is reviewed regularly by a body of other consultants) they would then progress to doing a more complex part of the procedure e.g. for keyhole surgery, the surgeon might let them operate/move the "port" (sorry surgeons, it's been decades since I knew the right terms!) and check their knowledge at that point - can you identify the gall bladder? what's that structure there? where are the blood vessels/nerves supplying it? ,moving onwards to doing a part of the operation, and finally a full operation under supervision. It's very carefully monitored, and I hope that if you speak to the consultant you might be reassured - it's ok to ask - what parts of the surgery will the consultant be doing, and what parts will someone else be doing, and I hope that will make you feel more confident.
It's completely possible that the anaesthetist may not be a consultant either , and you are trusting them with more than an eye.
My kids are grown up, but I would have no issues whatsoever in consenting for a "trainee" to do the operation on me or any of my family.
I hope all goes well for your child.