title: Visual Dysfunction of Type I and VI Mucopolysaccharidosis Patients Evaluated with Visual Evoked Cortical Potential.
abstract: OBJECTIVE
  To evaluate the visual system of patients suffering from type I or VI mucopolysaccharidosis (MPS) by recording the visual evoked cortical potential (VECP).
  
  
  METHODS
  Two patients with MPS VI and 2 patients with MPS I were tested before and after enzyme replacement therapy (ERT). A control group of 20 subjects was tested for statistical comparison. VECP was elicited by monocular stimulation with 1-Hz phase-reversal checkerboard patterns at 0.5 and 2 cycles per degree and with 16° of visual field. In all patients, both eyes were tested. VECP amplitude and latency were measured and compared with tolerance limits obtained from controls.
  
  
  RESULTS
  MPS I and VI patients have a severe visual impairment that can be quantified by measuring VECPs. Even after several weeks of ERT, the visual impairment remained unaltered, indicating that the treatment had no significant influence on the visual conditions of MPS patients. Visual responses to high spatial frequencies were more deeply impaired than responses to low spatial frequencies. This can be explained by the kind of damage in the visual system that preferentially targets the eye optics.
  
  
  CONCLUSIONS
  VECPs can be used to monitor the degree of visual impairment of MPS patients and to check ERT efficacy.
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Porto Alegre, Brasil.
authors.forename: Bruno Duarte
authors.initials: BD
authors.lastname: Gomes
authors.forename: Givago da Silva
authors.initials: Gda S
authors.lastname: Souza
authors.forename: Gustavo Monteiro
authors.initials: GM
authors.lastname: Viana
authors.forename: Isabel Cristina Neves
authors.initials: IC
authors.lastname: de Souza
authors.forename: Patricia do Socorro Queiroz
authors.initials: Pdo S
authors.lastname: Feio
authors.forename: Ida Vanessa Doederlein
authors.initials: IV
authors.lastname: Schwartz
authors.forename: Diane Ruschel
authors.initials: DR
authors.lastname: Marinho
authors.forename: Manoel da Silva
authors.initials: Mda S
authors.lastname: Filho
authors.forename: Roberto
authors.initials: R
authors.lastname: Giugliani
authors.forename: Luiz Carlos de Lima
authors.initials: LC
authors.lastname: Silveira
authors.forename: Luiz Carlos Santana
authors.initials: LC
authors.lastname: da Silva