How long does it take to fix lazy eye by patching?

Months to years: Depending upon the severity of the defect and the age of the patient, patching can be effective for years. Sometimes we need to do maintenance patching to reduce the chances of the newly strengthened eye from becoming weak again.

Long time: Depends on age (older = harder), severity of deviation, the amount of amblyopia, visual acuity, etc. Patching may be done in combination with other therapies.