A case of functional visual loss diagnosed through bilateral randomized visual field testing with a trick method.

Purpose: To report a case of functional visual loss (FVL) diagnosed through bilateral randomized visual field testing using Imo vifa with a trick method. Observations: A 27-year-old man complained of visual field abnormality in his left eye after falling from a height of 4 m. The left eye had a best-corrected visual acuity (BCVA) of 20/16 and a critical flicker frequency (CFF) of 44.5 Hz at the first visit. Commotio retinae was observed in the inferior retina of the left eye, and the pupillary light reflex was normal. Computed tomography and magnetic resonance imaging of the head revealed no abnormalities. However, the Goldmann perimeter (GP) showed constriction of visual field in the left eye. Since traumatic optic neuropathy was suspected initially; therefore, two courses of methylprednisolone pulse therapy were administered. However, the BCVA and CFF gradually worsened to 20/200 and 14 Hz, respectively. Nevertheless, his pupillary light reflex was still normal, and GP showed a spiral visual field. Thus, we suspected that this was a case of FVL and performed bilateral randomized visual field testing using Imo vifa in three steps as a trick method. In the first step, we performed the normal method for bilateral randomized visual field testing. In the second and third steps, we explained to the patient that only the right or left eye would be examined on purpose; bilateral randomized visual field testing was then performed. The results of examinations revealed left homonymous hemianopsias and normal and concentric contraction of the visual field in both eyes. These results could not be explained by organic disease, and the patient was diagnosed with FVL. Conclusions and Importance: Bilateral randomized visual field testing using Imo vifa with a trick method was useful for diagnosing FVL.