It was long thought that lazy eye wasn't treatable in adults after a "critical age" of 8-10 years old. It has recently been shown that this isn't the case, and that amblyopia can be improved in adulthood. The brain is far more plastic than most people previously thought, new treatments based on new techniques can offer improvement. Amblyopia Treatment: Results of PEDIG Studies, David K. Wallace">
Vision therapy can be done at home, with special software, and under the guidance of vision therapists and optometrists.
Patching is the practice of covering the strong eye with an eye patch so that only the weak eye can be used. Patching only works in about 50% of cases. Lazy eye recurs in 21% of people where patching is successful. Amblyopia Treatment: Results of PEDIG Studies, David K. Wallace">
Eye drops are a kind of chemical patching. When used they blur the vision of the strong eye, forcing the person to use their lazy eye.
Surgery is often considered to correct the angle of deviation in people who have strabismus. It is often considered purely cosmetic, and doesn't usually result in better vision.