When caught early (before 9 years of age?), like in your sister's case, the "good" eye is covered so that the lazy eye is retrained. My case was caught relatively late, when I was in primary school, and I cheated (removing the patch) to read... In adults, there is some controversy -- most ophtalmologists will tell you there is no chance of retraining, a few suggest that it might be possible, after a long time. I guess it may also depend on the cause of amblyopia. Many cases are due to strabismus, some are caused by other problems. In my case, it seems my left eye was farsighted. There is some ongoing research about retraining in adults, e.g. professor Zhong-Lin Lu, in USC's Laboratory of Brain Processes (
LOBES).
The reason I have not had LASIK is that I don't like even the low risk it presents -- I rely on the one eye that would get the surgery.