Unilaterally extinguished electroretinograms in an eye with normal visual acuity and visual field

Purpose This study reports a case of unilateral retinopathy with extinguished full-field ERGs (ffERGs), wherein the visual acuity was 16/16 and the visual field was spared. Methods Observational case report. Results A 39-year-old female had developed nyctalopia in her left eye. Two years later, she visited an ophthalmologist who noted a bilaterally reduced pigmentation of the fundus. Her best-corrected visual acuity was 16/16 in both the eyes. Goldmann perimetry demonstrated that her visual field was bilaterally fully spared. ffERGs measurement was performed in accordance with the ISCEV standard protocol and indicated that her right eye was normal. However, all ERG responses were severely attenuated in her left eye. Multifocal ERG responses were found to be normal in the right eye and extinguished in the left eye except for residual responses that were exclusively located at the center. During the 7 years of the follow-up period, the visual field in the left eye, which was once normal, became shaded, and the development of a ring scotoma was identified. The visual field in the right eye is still full. Conclusions The pathogenesis of this patient's condition still remains unknown, while unilateral retinitis pigmentosa, unilateral pigmentary retinopathy, acute zonal occult outer retinopathy, and autoimmune retinopathy can all be considered as possible explanations. The uniqueness of this case study is that the extinguished ERG responses are predictive of the functional alteration in the affected eye, when the initial visual acuity and the visual field were normal.