This feature is currently available for iOS users in UK, Singapore, Canada, South Africa, and Australia regions only.
The Lens correction tool fixes lens issues such as distortion, chromatic aberration, vignette, and perspective. Since each lens is uniquely designed, the lens corrections are applied depending upon your lens model.
To apply these lens corrections and fix these lens issues:
The Enable Lens Corrections toggle remains disabled for photos that do not have any lens issues.