title: Changes in the ERG d-wave with vigabatrin treatment in a pediatric cohort.
abstract: OBJECTIVE
  Vigabatrin (VGB), a treatment for the childhood epilepsy, infantile spasms (IS), is implicated in visual field constriction. Electroretinograms (ERGs) are used as a substitute for visual field testing in infants. We use the VGB-associated ERG reduction (VAER), defined as reduction in age-corrected light adapted 30 Hz flicker amplitude from a pre-treatment measurement in the absence of other retinal defects, as an indicator of retinal toxicity resulting from VGB use. The d-wave ERG response is predominantly the result of OFF-bipolar cell depolarization response to light offset. The purpose of this study is to evaluate the ERG d-wave response as a marker for VAER toxicity in an infant population.
  
  
  METHODS
  One hundred children with IS treated with VGB (median age at baseline: 7.6 months; range 1.7-38.4) were tested for the cone-OFF response elicited to a 250 cd s m(2) flash with 200 ms duration (long flash ERG). Diagnosis of VAER requires baseline testing of the flicker ERG and at least one follow up ERG; Fifty-one patients fulfilled this criteria. Fifty-eight children received the long flash ERG at baseline. Thirteen retinally normal controls with a median age of 32 months (5.7-65) were also tested. Amplitude and implicit time of the d-wave response were measured manually.
  
  
  RESULTS
  Longer duration of treatment was associated with reduced d-wave amplitude (ANOVA p < 0.05) in patients taking VGB. Nine patients demonstrated VAER during the course of the study. D-wave amplitude was reduced in the IS group with VAER compared to those without VAER (p < 0.05).
  
  
  CONCLUSIONS
  Vigabatrin associated retinal defects may be reflected in reduction of the cone d-wave amplitude.
authors.affiliation: Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Rachel
authors.initials: R
authors.lastname: Dragas
authors.forename: Carol
authors.initials: C
authors.lastname: Westall
authors.forename: Tom
authors.initials: T
authors.lastname: Wright
mesh_terms: D000927:Anticonvulsants / Q000009:adverse effects* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D004596:Electroretinography / Q000187:drug effects*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D010775:Photic Stimulation; D012160:Retina / Q000503:physiopathology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D012164:Retinal Diseases / Q000139:chemically induced* / Q000503:physiopathology; D013036:Spasms, Infantile / Q000188:drug therapy*; D020888:Vigabatrin / Q000009:adverse effects* / Q000627:therapeutic use; D014792:Visual Acuity / Q000187:drug effects; D014794:Visual Fields / Q000187:drug effects
chemical_list: D000927:Anticonvulsants; D020888:Vigabatrin