Can a child suffer from retinal hemorrhage from falling off a couch onto a hard wooden floor?

Unlikely: Depends upon the severity of the fall and the location of the hemorrhage. If there is severe head trauma then hemorrhages may be observed at the optic nerve. Eyes are generally well protected and without direct eye trauma or an orbital fracture, eye damage is unlikely. If the child is an infant, suspicion of non-accidental trauma could be entertained. You need full documentation.

Possible: But depends on severity (height of fall, age of patient) and any retinal or brain hemorrhages in a child not consistent with the story = non-accidental trauma or "shaken baby".