title: Vigabatrin retinopathy in an Irish cohort: lack of correlation with dose.
abstract: OBJECTIVE
  The anticonvulsant vigabatrin (VGB) causes irreversible visual-field constriction in 19-92% of patients. It is unclear whether this correlates with dosing, and the natural history of the retinopathy remains obscure. We conducted a retrospective analysis of patients receiving long-term VGB to examine whether toxicity is related to the daily dose, duration of therapy, or cumulative dose.
  
  
  METHODS
  Information from 93 patients taking long-term, stable VGB therapy was analyzed. We recorded data on patient demographics, VGB dosing, and all visual-field assessments. We used the mean redial degrees (MRD) from the right eye to compare the amount of constriction with the dose of VGB.
  
  
  RESULTS
  The mean number of assessments was two (range, 1-6). Of patients having more than one assessment (n = 65), the mean follow-up time was 2.4 years (range, 0.7-5.6 years); in 52.7%, visual-field constriction developed. Male and female patients were affected equally. We found no correlation between the average MRD and either the maximum dose of VGB taken, the duration of exposure, or the cumulative dose. The shortest exposure time to development of constriction was 1.1 years. All patients with normal fields on initial assessment continued to have normal fields on follow-up. Most patients who had evidence of constriction on initial assessment and remained taking VGB showed no progression on follow-up. One patient had a substantial recovery of vision after discontinuation of VGB.
  
  
  CONCLUSIONS
  Development of visual constriction in patients receiving prolonged, standard doses of VGB does not depend on the daily dose, duration of exposure, or cumulative dose. Other contributing factors were not identified. Our data suggest that field defects may develop within the first few years of therapy and possibly remain stable thereafter.
authors.affiliation: Department of Clinical Neuroscience, Beaumont Hospital, Dublin 9, Ireland.
authors.forename: Peter
authors.initials: P
authors.lastname: Kinirons
authors.forename: Gianpiero L
authors.initials: GL
authors.lastname: Cavalleri
authors.forename: Dierdre
authors.initials: D
authors.lastname: O'Rourke
authors.forename: Colin P
authors.initials: CP
authors.lastname: Doherty
authors.forename: Irene
authors.initials: I
authors.lastname: Reid
authors.forename: Patricia
authors.initials: P
authors.lastname: Logan
authors.forename: Brenda
authors.initials: B
authors.lastname: Liggan
authors.forename: Norman
authors.initials: N
authors.lastname: Delanty
mesh_terms: D000328:Adult; D000927:Anticonvulsants / Q000009:adverse effects* / Q000627:therapeutic use; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D012164:Retinal Diseases / Q000139:chemically induced* / Q000175:diagnosis / Q000453:epidemiology*; D012189:Retrospective Studies; D012737:Sex Factors; D020888:Vigabatrin / Q000009:adverse effects* / Q000627:therapeutic use; D014787:Vision Tests; D015354:Vision, Low / Q000139:chemically induced* / Q000175:diagnosis / Q000453:epidemiology; D058609:Visual Field Tests; D014794:Visual Fields / Q000187:drug effects
chemical_list: D000927:Anticonvulsants; D020888:Vigabatrin