To cite the package 'visualFields' in publications use:

Marin-Franch I & Swanson WH. The visualFields package: A tool for analysis and visualization of visual fields. Journal of Vision, 2013, 13(4):10, 1-12 (R package version 0.4).

Corresponding BibTeX entry:

  @Article{,
    title = {The visualFields package: A tool for analysis and
      visualization of visual fields},
    author = {Ivan Marin-Franch and William H Swanson},
    year = {2013},
    note = {R package version 0.4},
    journal = {Journal of Vision},
    volume = {13},
    number = {4},
    pages = {10, 1-12},
    doi = {10.1167/13.4.10},
  }