Clinical feature and waveform in infantile nystagmus syndrome in children with FRMD7 gene mutations

Infant nystagmus sydrome presents as involuntary eye movement disorder and can affect seriously ocular function. We performed a retrospective study of clinical data and FRMD7 genetic test results in 12 cases of infantile nystagmus syndrome to correlate waveform, stereopsis, and visual acuity. The patients（age 6.40±2.67 years） had FRMD7 mutations as follows： missense in eight cases, shear in two cases, frameshift in one case, and non-frameshift in one case. Horizontal jerk waveform was observed in six cases, versus horizontal pendulum in five cases and dual jerk in one case. The uncorrected visual acuity（24 eyes） was 0.21±0.12,compared with a corrected visual acuity（24 eyes） of 0.32±0.14. All patients had simultaneous perception, versus fusion function in 10 cases（83.33%） and stereoscopic vision in seven cases（58.33%） using the synoptophore. Eleven cases（91.67%） detected the stereo fly, compared with five cases（41.67%） for stereoscopic circles and seven cases（58.33%） for stereoscopic animals by Titmus test. Stereoscopic vision using the synoptophore did not correlate with the frequency, amplitude, or intensity of nystagmus or with corrected binocular visual acuity. The infantile nystagmus syndrome with FRMD7 mutations in our cases was caused primarily de novo and missense mutations. Visual acuity and binocular visual function were significant impaired, and the waveform was generally horizontal jerk. Also, an infrared videonystagmogram can record the frequency, amplitude, and intensity of nystagmus accurately.