I am currently working with 2 children with similar issues. Age 7 and 9. the 9 year old is going for several consultations for possible surgery.
You are on the right track tapping for emotions and aspects. The one that stands out for me and my clients is the BELIEF system. I have watched almost all of Gary's DVD's. and one of things that somes accross as you see him work with people is the BELIEF system. Several of his clients had such a strong belief and language that they had acquired from the various medical professionals.
I would tap on the belief that the eyes can be balanced naturally. Such as even tho I , parents, physicians, etc believe that surgery is the best way to correct my eyes. .. . . I forgive. .. . . etc. then place "in circuit" I believe differently, I believe it is possible to balance my eyes and the muscles ( use all the terms the medical professionals use as different aspects) balance naturallly.
Keep me posted.
one other idea. because you are related to this child, I would consider having a session ( can be via phone) with an experienced practitioner who might get to aspects that you aren't seeing.
Best to you for using this terrific technique on your grandchild.
Cindy