Optokinetic nystagmus (OKN) drum
Answer: B. Optokinetic nystagmus (OKN) drum
Explanation: A number of tests can be used to determine whether a patient has functional visual loss. Direct tests do not require the patient to verbally respond or interpret the visual information. Tests such as the swinging light test, OKN response, and mirror test make it very difficult for a patient to feign disease. Indirect tests rely on the patient’s cooperation and allow more definite measurement of visual acuity in the “injured” eye.