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A reduced visual pathway response in infantile nystagmus syndrome
John P Kelly1, Kristina Tarczy-Hornoch1, James O Phillips2
1Division of Ophthalmology, Roger H. Johnson Vision Lab, Seattle Children's Hospital, Seattle, Washington; Department of Ophthalmology, University of Washington Medical Center, Seattle.
Insights
Infantile nystagmus syndrome (INS) in children reduces visual cortical responses. However, selective averaging of visual evoked potential (VEP) data reveals enhanced responses during brief foveation periods, suggesting improved visual processing.
Area of Science:
- Neuroscience
- Ophthalmology
- Pediatric Vision
Background:
- Infantile nystagmus syndrome (INS) is a condition characterized by involuntary eye movements.
- The impact of INS on visual cortical processing and the role of foveation periods remain areas of active investigation.
- Understanding these aspects is crucial for developing effective interventions for children with INS.
Purpose of the Study:
- To investigate visual cortical responses in children diagnosed with infantile nystagmus syndrome (INS).
- To explore the potential contribution of foveation periods to visual processing in INS.
- To determine if enhanced signal extraction methods can reveal underlying visual capabilities.
Main Methods:
- Retrospective review of visual evoked potential (VEP) recordings in 26 children with INS.
- Objective selective averaging technique applied to VEP data for extracting consistent signal periods.
- Comparison of VEP parameters (amplitude, latency, SNR) with published age-matched controls.
- Correlation of relative foveation (from video-oculography) with VEP measures.
Main Results:
- Selective averaging significantly increased VEP amplitude and SNR in children with INS (270%-420%) compared to standard averaging.
- The enhancement in VEP response was more pronounced for reversing checkerboards than grating onset.
- Relative foveation positively correlated with VEP amplitude and the number of trials selected for averaging.
Conclusions:
- Nystagmus in INS likely diminishes overall visual cortical response.
- Brief periods of foveation during nystagmus allow for the extraction of significantly larger cortical signals.
- This supports the hypothesis that the INS visual system can generate robust cortical signals during these transient foveal fixation periods.
Purpose:
To investigate visual cortical responses in children with infantile nystagmus syndrome (INS) and the potential contribution of foveation periods.
Methods:
The medical records of children with INS who had visual evoked potential (VEP) recordings to reversing checkerboards and onset of horizontal gratings were reviewed retrospectively. VEP recordings underwent objective selective averaging for extraction of brief periods having consistent amplitude and timing with the stimulus presentation. VEP amplitude, latency, and signal-to-noise ratios (SNR) were compared to results from published age-matched controls under the same conditions. Relative foveation in INS subjects was determined from the proportion of time a video-oculography recording met eye position and velocity criteria.
Results:
A total of 26 children met inclusion criteria. Selective averaging increased VEP amplitude and SNR in INS by 270%-420% compared to standard averaging (P < 0.0001). The INS change in VEP response was greater for reversing checkerboard stimulation than horizontal-grating onset and was significantly greater than that in controls (P < 0.001). Latency was not changed by selective averaging. Relative foveation was correlated with increasing VEP amplitude (P = 0.02) and number of trials chosen for selective averaging (P < 0.01). After selective averaging, relative foveation correlated with VEP amplitude to reversing checkerboards only (P = 0.007).
Conclusions:
Nystagmus likely causes a reduced visual cortical response in children with INS. A significantly larger response can be extracted from brief periods during nystagmus eye movements, supporting the hypothesis that the INS visual system generates a larger cortical signal during brief foveation periods.
