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Field-specific visual-evoked potentials: identifying field defects in vigabatrin-treated children
G F A Harding1, E L Spencer, J M Wild
1Neurosciences Research Institute, Aston University, Birmingham, UK. g.f.a.harding@aston.ac.uk
Insights
A new visual-evoked potential (VEP) technique effectively identifies vigabatrin-associated visual field defects in children. This method is well-tolerated and accurate for young epilepsy patients unable to complete traditional perimetry.
Area of Science:
- Ophthalmology
- Neuroscience
- Pediatric Neurology
Background:
- Vigabatrin treatment in epilepsy is associated with visual field loss.
- Assessing visual field defects in young children (<9 years) is challenging with standard perimetry.
- Pediatric populations require specialized methods for visual field assessment.
Purpose of the Study:
- To develop and validate a visual-evoked potential (VEP) technique for identifying visual field defects.
- To assess the efficacy of a field-specific VEP in children with epilepsy treated with vigabatrin.
- To provide an alternative to perimetry for non-cooperative pediatric patients.
Main Methods:
- Developed a field-specific VEP using central and peripheral stimuli with varying check sizes and reversal rates.
- Recorded electroretinograms (ERG) to assess retinal function.
- Compared the diagnostic performance of the field-specific VEP with standard perimetry in 39 children (aged 3-15 years).
Main Results:
- The field-specific VEP was tolerated by 35 of 39 children.
- The VEP demonstrated a sensitivity of 75% and a specificity of 87.5% in identifying visual field defects compared to perimetry.
- Electroretinogram (ERG) 30-Hz flicker amplitude was also a useful indicator of visual field loss.
Conclusions:
- Field-specific VEPs are a well-tolerated and accurate method for children over 2 years old.
- This VEP technique is sensitive and specific for detecting vigabatrin-associated peripheral field defects.
- The VEP offers a viable alternative for visual field assessment in young children undergoing vigabatrin therapy.
Objective:
To derive a visual-evoked potential (VEP) technique for identifying visual field defects in children with epilepsy treated with vigabatrin and unable to perform perimetry.
Background:
Studies have linked vigabatrin to a specific pattern of visual field loss. Few studies have included the pediatric population because of difficulties in assessing the visual field by perimetry below a developmental age of 9 years.
Methods:
A field-specific VEP was developed with a central (0 degrees to 5 degrees radius) and peripheral stimulus (30 degrees to 60 degrees radius). Stimuli consisted of black and white checks that increased in size with eccentricity. Checks reversed at different rates, allowing separate central and peripheral responses to be recorded. Five vigabatrin-treated young adults with field defects were identified using this stimulus. Electroretinograms (ERG) were recorded to examine the effects of vigabatrin on retinal function. Thirty-nine children aged 3 to 15 years were included in the study. Twelve patients were examined by both the field-specific stimulus test and perimetry. The diagnostic performance of the field-specific stimulus test was compared with that of perimetry.
Results:
Thirty-five of 39 children complied with the field-specific stimulus, 26 of 39 complied with the ERG, and 12 of 39 complied with perimetry. Using the summed amplitude of the peripheral response from O(2) and O(1), responses below 10 microV were deemed abnormal. The field-specific stimulus identified 3 of 4 abnormal perimetry results and 7 of 8 normal perimetry results, giving a sensitivity of 75% and a specificity of 87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude, with a cutoff below 70 microV, gave a useful indication of visual field loss.
Conclusion:
Field-specific VEP are well tolerated by children older than 2 years of age and are sensitive and specific in identifying vigabatrin-associated peripheral field defects.