Final answer:
The nurse should instruct the patient with homonymous hemianopsia to turn the head to scan the environment to reduce the risk of falls when ambulating.
Step-by-step explanation:
To reduce the risk of falls when ambulating for a client who has homonymous hemianopsia as a result of a stroke, the nurse should instruct the patient to turn the head to scan the environment. This helps compensate for the lost visual field by allowing the client to gain a full view of the surroundings, thus minimising potential hazards. It's crucial for the nurse to educate the patient on safe ambulation techniques and to ensure a safe environment to prevent falls.