title: Effect of eyelid saccades on the position of lateral canthus in young and older subjects.
abstract: OBJECTIVE
  To measure the effect of down and upgaze on lateral canthus height.
  
  
  METHODS
  Observational study. The lateral canthus height of 125 eyes was quantified in the primary position, up, and downgaze. All measurements were monocular. The sample comprised 125 subjects divided into three age groups: 10 to 30, 31 to 50, and 51 to 70 years. All images were acquired with a digital camera and processed with the NIH image software.
  
  
  RESULTS
  The lateral canthus height was influenced by both age and position of gaze. Compared to the primary position of gaze, the mean lateral canthus height decreased significantly in downgaze for all age groups (1.51 mm for group 1, 1.72 mm for group 2, and 2.3 mm for group 3). Upgaze increased the height of the lateral canthus only for groups 2, and 3 (0.66 mm and 0.87 mm, respectively).
  
  
  CONCLUSIONS
  The height of the lateral canthus is strongly influenced by upper and lower eyelid movements. The combined action of contraction of the lower eyelid retractors and relaxation of the levator muscle diminishes the height of the lateral canthus in all age groups. This effect is more pronounced in older subjects, probably reflecting the typical lateral canthal tendon laxity of the aging process.
authors.affiliation: School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil. aavecruz@fmrp.usp.br
authors.forename: Antonio Augusto V
authors.initials: AA
authors.lastname: Cruz
authors.forename: Deborah B Fernandes
authors.initials: DB
authors.lastname: Távora
authors.forename: Luiz Fernando Taranta
authors.initials: LF
authors.lastname: Martin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000886:Anthropometry; D002648:Child; D005123:Eye / Q000033:anatomy & histology; D005143:Eyelids / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012438:Saccades / Q000502:physiology*