The role of electrophysiology tests and multimodal imaging in evaluation of nystagmus

Abstract

Purpose This work aimed to highlight the role of electrophysiology testing and multimodal imaging in evaluation of nystagmus. Patients and methods This is a retrospective multi-centered analytic study that recruited patients with nystagmus from the outpatient clinics referred to the electrophysiology units of the hospitals of the University of Minia, Ain Shams, Banha, and Cairo, Egypt. The study included 60 (120 eyes) patients. The performed investigations included full-field electroretinography (ffERG), pattern electroretinography, flash visual evoked potential (FVEP), pattern visual evoked potential, optical coherence tomography (OCT), OCT-angiography (OCT-A), and fundus autofluorescence (FAF), whenever possible. Results There were no or minimal detectable fundus changes in 78 (65%) eyes, of which 40 (33.3%) eyes showed severe loss of photopic responses on ffERG, with Bull’s eye pattern observed on FAF and loss of foveal photoreceptors in OCT, while 18 (12.5%) eyes showed reduced photopic and scotopic responses in ffERG with loss of foveal photoreceptors and thinned parafovea in OCT, 14 (11.7%) eyes showed average photopic and scotopic responses with different stages of foveal hypoplasia in OCT and OCT-A, and six (5%) eyes showed normal results in tests assessing the function and structure of the macula and optic nerve, including ERG, FVEP, and OCT. On the other hand, macular or optic nerve abnormalities were observed in 42 (35%) eyes, of which 20 (16.7%) eyes showed significant loss of photopic responses in ffERG and abnormal fovea in OCT and FAF tests, 10 (8.3%) eyes showed loss of photopic and scotopic responses in ffERG and abnormal results in the OCT and FAF, four (3.3%) eyes had normal results in ERG and FVEP, but showed fovea hypoplasia in OCT, and eight (6.7%) eyes had normal photopic and scotopic responses by ffERG, but with abnormal visual evoked potential responses and thinning of the nerve fiber layer in the OCT. Conclusion Electrophysiological tests and multimodal imaging are crucial to diagnosing the underlying causes of nystagmus, especially in patients with normal fundus.